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Systemic Exposure (systemic + exposure)

Distribution by Scientific Domains

Medical Sciences	80%
Chemistry	19%

Distribution within Medical Sciences

Pharmacology & Pharmaceutical Medicine	35%
Dermatology	8%
11 Other Subdomains	57%

Selected Abstracts

Inflammatory pathways between placenta and foetus

ACTA PAEDIATRICA, Issue 1 2001
Mikko Hallman
Recent evidence indicates that intra-amniotic endotoxin (LPS) and interleukin-1 alpha (IL-1,) accelerate foetal lung maturity and protect from respiratory distress syndrome (RDS) more effectively than does antenatal glucocorticoid. Inflammatory cytokines promote development of chronic lung disease in the premature, acute RDS (ARDS) in children and adults. Systemic exposure to LPS or cytokines can result in generalized multiorgan damage. The abnormal host defence in the foetus and the premature newborn need to be considered in therapeutic interventions. [source]

Clinical Pharmacokinetics of Frovatriptan

HEADACHE, Issue 2002
P. Buchan PhD
Objective.,To review available data on the clinical pharmacokinetics of frovatriptan. Background.,Preclinical data suggest that the pharmacokinetic profile of frovatriptan may differ from that of the currently available triptans. Methods.,Studies of healthy volunteers, subjects with renal or hepatic impairment, elderly subjects, and patients with migraine during and between attacks were reviewed. Results.,Oral bioavailability of frovatriptan is 22% to 30%, and although the time to maximum concentration is typically 2 to 3 hours, approximately 60% to 70% of plasma maximum concentration is achieved within 1 hour of dosing. Frovatriptan distributes into erythrocytes, with binding reversible and time dependent. The relatively long terminal elimination half-life (about 26 hours) confers good systemic exposure and may produce a long duration of therapeutic action, thus reducing migraine recurrence and the need for redosing. Systemic exposure to frovatriptan generally correlates with dose between 1 and 100 mg. Blood and plasma frovatriptan concentrations are consistently higher in females, but there is no need to adjust dose according to gender. Pharmacokinetics are essentially unaffected by food and were predictable after repeat dosing; steady state is approached in about 4 to 5 days. Pharmacokinetics were changed only slightly in subjects with renal impairment or mild-to-moderate hepatic impairment, elderly individuals, and during migraine attacks. Frovatriptan is principally metabolized by the CYP1A2 isoenzyme of cytochrome P-450 and is cleared by the kidney and liver, each having sufficient capacity to compensate for impairment of the other. Conclusions.,Frovatriptan can be taken without regard for food intake, and because of the large therapeutic margin and shallow dose-response curve, there is no need for dosage adjustment in the elderly, in women taking a combined oral contraceptive, in patients with mild-to-severe renal impairment, mild-to-moderate hepatic impairment, or according to gender. The long duration of exposure may reduce the likelihood of early migraine recurrence. [source]

Lipopolysaccharide exposure is linked to activation of the acute phase response and growth failure in pediatric Crohn's disease and murine colitis,

INFLAMMATORY BOWEL DISEASES, Issue 5 2010
Brad A. Pasternak MD
Abstract Background: Systemic exposure to lipopolysaccharide (LPS) has been linked to clinical disease activity in adults with inflammatory bowel disease (IBD). We hypothesized that markers of LPS exposure and the acute phase response (APR) would be increased in pediatric IBD patients with growth failure, and that LPS signaling would be required for induction of the APR in murine colitis. Methods: Serum markers of LPS exposure, endotoxin core IgA antibody (EndoCAb), and the APR, LPS binding protein (LBP) were quantified in pediatric IBD patients and controls. LBP and cytokine production were determined after administration of trinitrobenzene sulfonic acid (TNBS) enemas to mice with genetic deletion of Toll-Like receptor 4 (TLR4), and wildtype (WT) controls. Results: Serum EndoCAb and LBP were significantly elevated in patients with Crohn's disease (CD), compared to disease controls with ulcerative colitis (UC) and healthy controls (P < 0.001). This was independent of disease activity or location. CD patients with elevated serum EndoCAb and LBP exhibited linear growth failure which persisted during therapy. Serum LBP increased in WT mice following TNBS administration, in conjunction with increased serum TNF-,, IL-6, and IL-10, and expansion of regulatory T-cell numbers. Both the APR and expansion of foxp3+ T cells were abrogated in TLR4-deficient mice, in conjunction with a reduction in acute weight loss. Conclusions: LPS exposure and a persistent APR are associated with growth failure in pediatric CD. LPS signaling is required for the APR in murine colitis. Therapies targeting this pathway may benefit the subset of patients with refractory growth failure. (Inflamm Bowel Dis 2010) [source]

Pharmacokinetics of mesalazine pellets in children with inflammatory bowel disease

INFLAMMATORY BOWEL DISEASES, Issue 5 2004
Heleen Wiersma MD
Abstract Mesalazine is a first-line drug in pediatric inflammatory bowel disease (IBD), and is customarily used to induce and maintain remission in mild to moderate disease. In children, pharmacokinetic data are scarce, and dosage recommendations are largely extrapolated from studies in adults. Aim of the study was to obtain the pharmacokinetic profile of a new mesalazine pellet formulation in children with ulcerative colitis and Crohn's colitis. A single oral dose of 20 mg/kg mesalazine was administered to 13 patients (age 6,16 years). Serial blood and urine sampling for determination of mesalazine and acetylmesalazine was performed before and during 24 hours following ingestion. Maximum plasma concentration of mesalazine (Cmax) was 1332 ng/mL (geometric mean, geometric coefficient of variation [CV]: 0.57), obtained 3.7 hours (tmax; CV: 0.31) after drug administration. Systemic exposure as determined by area under the plasma concentration-time curve (AUC0,, ) was 8712 ng/ml*h (CV: 0.44). Terminal half-life of elimination of mesalazine was 3.5 hours (t1/2; CV: 1.43). This study presents extensive pharmacokinetic data on mesalazine in children with mild-moderately active ulcerative colitis and Crohn's colitis. In comparison with previous experience in adults, pharmacokinetics of mesalazine administered as pellets appear to be similar in both populations. [source]

Combined Therapy with Atorvastatin and Calcineurin Inhibitors: No Interactions with Tacrolimus

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 9 2005
W. P. D. Lemahieu
Increased systemic exposure to statins and consequent risk for complications has been reported in patients concomitantly treated with cyclosporin A (CsA). This has been ascribed to inhibition of drug catabolism by cytochrome P450 3A4 (CYP3A4) or drug transport by P-glycoprotein (PGP) and organic anion transporting polypeptide (OATP1B1). It is not known whether the combination of statins and tacrolimus (Tac) also suffers from this drawback. Therefore, a pharmacokinetic study of atorvastatin and its metabolites was performed in 13 healthy volunteers after 4 days' treatment, and after short (12 h) concomitant exposure to CsA and Tac. A complementary assessment of overall CYP, and hepatic and intestinal CYP3A4 + PGP activity was performed after each treatment episode and compared to baseline (no drugs). Systemic exposure to atorvastatin acid and its metabolites was significantly increased when administered with CsA. In contrast, intake of Tac did not have any impact on atorvastatin pharmacokinetics. Concomitantly, a profound decrease of hepatic and intestinal PGP and an increase of intestinal CYP3A4 were noted with CsA, whereas no effect was seen after atorvastatin therapy with or without Tac. Based on these findings treatment with Tac appears a safer option for patients needing a combination of statins and calcineurin inhibitors. [source]

CYP2C19 Polymorphism and Proton Pump Inhibitors

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 1 2004
Ulrich Klotz
In different populations three phenotypes have been identified: extensive metabolizers, poor metabolizers and individuals carrying one wild type and one mutant allele (het extensive metabolizers). Systemic exposure to the proton pump inhibitors as expressed by the AUC (area under the plasma level time profiles) is 5,12-times higher in poor metabolizers than in extensive metabolizers. As the pharmacodynamic response (elevation of intragastric pH) to the proton pump inhibitors is related directly to their AUC, a much higher pH can be monitored over 24 hr in poor metabolizers than in extensive metabolizers. Furthermore, clinical efficacy of all proton pump inhibitors depend on maintaining intragastric pH above certain threshold levels and significantly higher eradication rates of Helicobacter pylori have been observed in patients of the poor metabolizers and het extensive metabolizers phenotype if compared to extensive metabolizers. Likewise, limited data suggest that proton pump inhibitors-induced healing rates in gastro-oesophageal reflux disease are apparently higher in poor metabolizers/het extensive metabolizers than in extensive metabolizers of CYP2C19. Therefore initial genotyping for this enzyme and higher dosage in extensive metabolizers is likely to improve the clinical efficacy of proton pump inhibitors. [source]

Pharmacokinetics of sildenafil after single oral doses in healthy male subjects: absolute bioavailability, food effects and dose proportionality

BRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 2002
Donald J. Nichols
Aims, To determine the absolute bioavailability, dose proportionality and the effects of food on the pharmacokinetics of single oral doses of sildenafil citrate. Methods, Three open-label, randomized crossover studies were conducted in healthy male subjects. Absolute bioavailability was determined by comparing pharmacokinetic data after administration of single oral and intravenous 50-mg doses of sildenafil (n=12 subjects). Food effects were examined by comparing pharmacokinetic data for sildenafil and its primary circulating metabolite, UK-103,320, after administration of a single oral 100-mg dose in the fasted and fed states (n=34 subjects). Dose proportionality was assessed from pharmacokinetic data obtained after administration of four single oral doses of sildenafil (25, 50, 100 and 200 mg) to 32 subjects. The safety and tolerability of sildenafil were also assessed in all of these studies. Results, The calculated absolute oral bioavailability of sildenafil was 41% (90% CI: 36,47). Food slowed the rate of absorption, delaying mean tmax by approximately 1 h and reducing Cmax by 29% (90% CI: 19,38). Systemic exposure, as assessed by the mean area under the plasma concentration,time curve (AUC), was reduced by 11% (90% CI: 6,16). These food effects were not considered to be of clinical significance. There was statistical evidence of nonproportionality in Cmax and AUC over the dose range 25,200 mg. However the degree of nonproportionality was small, with predicted increases in Cmax and AUC of 2.2- and 2.1-fold, respectively, for a doubling in dose, and was thought to be clinically nonsignificant. Sildenafil was well tolerated in the three studies; the majority of adverse events were mild and transient. Conclusions, Sildenafil had a mean absolute bioavailability of 41%. Food caused small reductions in the rate and extent of systemic exposure; these reductions are unlikely to be of clinical significance. Across the dose range of 25,200 mg, systemic exposure increased in a slightly greater than dose-proportional manner. [source]

Chronic Pharmacological and Safety Evaluation of HematideÔ, a PEGylated Peptidic Erythropoiesis-Stimulating Agent, in Rodents

BASIC AND CLINICAL PHARMACOLOGY & TOXICOLOGY, Issue 2 2009
Kathryn W. Woodburn
To support the safety of long-term dosing of chronic renal failure patients, a comprehensive toxicology programme was implemented including rat subchronic and chronic studies. Rats were administered 0, 0.1, 1 and 10 mg/kg of Hematide every 3 weeks for 3 months via subcutaneous injection or for 6 months via intravenous injection. The dosing period was followed by a 6-week follow-up period. The primary pharmacology of Hematide resulted in erythroid polycythemia as measured by elevated haemoglobin levels that were time- and dose-dependent. The pharmacology profiles were similar regardless of administration route. For example, for male rats at Day 90, subcutaneous dosing resulted in haemoglobin increases of 2.7, 4.5 and 6.9 g/dl for 0.1, 1 and 10 mg Hematide/kg respectively, compared to 2.8, 5.7 and 7.4 g/dl increases for intravenous dosing. Histopathological changes were related to the prolonged severe polycythemia induced in normocythemic animals administered an erythropoiesis-stimulating agent. The findings included extramedullary haematopoiesis in the spleen and liver, bone marrow hypercellularity and organ congestion. Microscopic findings were reversible, demonstrating a return towards control findings within 6 weeks following cessation of dosing. Systemic exposures, based on both area under the curve (AUC) and maximum concentration (Cmax), were substantially greater for intravenous than subcutaneous administration. No Hematide-specific antibodies were detected. In conclusion, Hematide is a potent erythropoiesis-stimulating agent, and the studies provide support for the safety of clinical development, including chronic dosing, for the treatment of anaemia associated with chronic renal failure. [source]

Drug-elicited systemic allergic (contact) dermatitis , update and possible pathomechanisms

CONTACT DERMATITIS, Issue 4 2008
Jacob Pontoppidan Thyssen
An allergic dermatitis reaction may develop after systemic exposure to a hapten that reaches the skin through haematogenous transport. This condition can be observed with and without previous cutaneous sensitization to the hapten but has traditionally been described following topical exposure. A heterogeneous clinical picture, in combination with limited insight to its pathomechanisms, makes such systemic reactions an area in need of further study. This article summarizes knowledge about systemic dermatitis elicited by drugs, with a special emphasis on possible pathomechanisms. A list of putative pathomechanisms is offered for future research. Literature was examined using PubMed,MEDLINE, EMBASE, Biosis, and Science Citation Index. Based on the literature, it is likely that humoral type 3, delayed-type hypersensitivity, and drug-driven (i.e. p-i concept) reactions are involved. As commonly used terms may be misleading because skin contact is not a prerequisite, we suggest that the term ,systemic allergic dermatitis' should be used in the future. [source]

Application of pharmacokinetic modelling to the routine therapeutic drug monitoring of anticancer drugs

FUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 4 2002
Annick Rousseau
Abstract Over the last 10 years, proofs of the clinical interest of therapeutic drug monitoring (TDM) of certain anticancer drugs have been established. Numerous studies have shown that TDM is an efficient tool for controlling the toxicity of therapeutic drugs, and a few trials have even demonstrated that it can improve their efficacy. This article critically reviews TDM tools based on pharmacokinetic modelling of anticancer drugs. The administered dose of anticancer drugs is sometimes adjusted individually using either a priori or a posteriori methods. The most frequent clinical application of a priori formulae concerns carboplatin and allows the computation of the first dose based on biometrical and biological data such as weight, age, gender, creatinine clearance and glomerular filtration rate. A posteriori methods use drug plasma concentrations to adjust the subsequent dose(s). Thus, nomograms allowing dose adjustment on the basis of blood concentration are routinely used for 5-fluorouracil given as long continuous infusions. Multilinear regression models have been developed, for example for etoposide, doxorubicin, carboplatin, cyclophosphamide and irinotecan, to predict a single exposure variable [such as area under concentration,time curve (AUC)] from a small number of plasma concentrations obtained at predetermined times after a standard dose. These models can only be applied by using the same dose and schedule as the original study. Bayesian estimation offers more flexibility in blood sampling times and, owing to its precision and to the amount of information provided, is the method of choice for ensuring that a given patient benefits from the desired systemic exposure. Unlike the other a posteriori methods, Bayesian estimation is based on population pharmacokinetic studies and can take into account the effects of different individual factors on the pharmacokinetics of the drug. Bayesian estimators have been used to determine maximum tolerated systemic exposure thresholds (e.g. for topotecan or teniposide) as well as for the routine monitoring of drugs characterized by a very high interindividual pharmacokinetic variability such as methotrexate or carboplatin. The development of these methods has contributed to improving cancer chemotherapy in terms of patient outcome and survival and should be pursued. [source]

Clinical Pharmacokinetics of Frovatriptan

Pimecrolimus in dermatology: atopic dermatitis and beyond

INTERNATIONAL JOURNAL OF CLINICAL PRACTICE, Issue 8 2005
Paolo Gisondi
Summary Pimecrolimus is a calcineurin inhibitor developed for the topical therapy of inflammatory skin diseases, particularly atopic dermatitis (AD). Pimecrolimus selectively targets T cells and mast cells. Pimecrolimus inhibits T-cell proliferation, as well as production and release of interleukin-2 (IL-2), IL-4, interferon-, and tumour necrosis factor-,. Moreover, pimecrolimus inhibits mast cell degranulation. In contrast to tacrolimus, pimecrolimus has no effects on the differentiation, maturation and functions of dendritic cells. In contrast to corticosteroids, pimecrolimus does not affect endothelial cells and fibroblasts and does not induce skin atrophy. Given the low capacity of pimecrolimus to permeate through the skin, it has a very low risk of systemic exposure and subsequent systemic side-effects. In different randomised controlled trials, topical pimecrolimus as cream 1% (Elidel®) has been shown to be effective, well tolerated and safe in both adults and children with mild to moderate AD. In addition, pimecrolimus has been successfully used in inflammatory skin diseases other than AD, including seborrheic dermatitis, intertriginous psoriasis, lichen planus and cutaneous lupus erythematosus. [source]

Synthesis of the stable isotope labeled antiviral nucleoside analog [8- 13C,7,9- 15N2]-ganciclovir

JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2006
Naiyu Zheng
Abstract Ganciclovir, a nucleoside analog of 2,-deoxyguanosine, is a drug used in suicide gene therapy for the treatment of mesothelioma. We required a stable isotope analog of ganciclovir for use in pharmacokinetic studies in order to monitor the systemic exposure of patients to the drug. Therefore, a facile and efficient synthesis of [8- 13C,7,9- 15N2]-ganciclovir, was devised. The synthesis was achieved in 4 steps with 25% total yield using commercially-available [8- 13C,7,9- 15N2]-guanine, without the need for purification of intermediates. The key step of the synthesis involved the coupling of [8- 13C,7,9- 15N2]-guanine with 3-propionyloxy-2-propionyloxy-methoxypropyl propionate. The latter was synthesized from a commercially available dichlorohydrin. Each step of the reaction could be easily monitored by liquid chromatography,mass spectrometry. The structure of the labeled ganciclovir was confirmed using 1H, 13C, and 15N nuclear magnetic resonance spectroscopy. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Intranasal delivery to the central nervous system: Mechanisms and experimental considerations

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 4 2010
Shyeilla V. Dhuria
Abstract The blood,brain barrier (BBB) limits the distribution of systemically administered therapeutics to the central nervous system (CNS), posing a significant challenge to drug development efforts to treat neurological and psychiatric diseases and disorders. Intranasal delivery is a noninvasive and convenient method that rapidly targets therapeutics to the CNS, bypassing the BBB and minimizing systemic exposure. This review focuses on the current understanding of the mechanisms underlying intranasal delivery to the CNS, with a discussion of pathways from the nasal cavity to the CNS involving the olfactory and trigeminal nerves, the vasculature, the cerebrospinal fluid, and the lymphatic system. In addition to the properties of the therapeutic, deposition of the drug formulation within the nasal passages and composition of the formulation can influence the pathway a therapeutic follows into the CNS after intranasal administration. Experimental factors, such as head position, volume, and method of administration, and formulation parameters, such as pH, osmolarity, or inclusion of permeation enhancers or mucoadhesives, can influence formulation deposition within the nasal passages and pathways followed into the CNS. Significant research will be required to develop and improve current intranasal treatments and careful consideration should be given to the factors discussed in this review. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1654,1673, 2010 [source]

In Vivo use of the P450 inactivator 1-aminobenzotriazole in the rat: Varied dosing route to elucidate gut and liver contributions to first-pass and systemic clearance

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2006
Timothy J. Strelevitz
Abstract The small intestine is regarded as an absorptive organ in the uptake of orally administered drugs, but also has the ability to metabolize drugs by both phase 1 and phase 2 reactions. The amount of drug that reaches the systemic circulation can be reduced by both intestinal and hepatic metabolism. 1-Aminobenzotriazole (ABT) is an irreversible inhibitor of cytochrome P450s. Through in vivo and in vitro studies, ABT has been evaluated for its utility in studying intestinal metabolism in rats. Rats have been exposed to ABT through varied routes of administration followed by p.o. and i.v. administration of midazolam (MDZ), a CYP3A substrate. The MDZ bioavailablity in rats dosed orally and in rats dosed intravenously with ABT is 58.5% and 0.7%, respectively (%F,=,2.3% w/o ABT). The approximately 80-fold difference between the two groups suggests the majority of the extraction occurs in the intestine following an oral dose. To further study the utility of ABT, the antihistamine fexofenadine (Fex), which is not significantly metabolized and is a substrate for the uptake and efflux transporters, OATP and P-gp, was tested in rat. There was no change in oral or systemic exposure of Fex when animals were predosed with ABT, suggesting that ABT does not affect these transporters. These findings may lead to a better understanding of the interdependent role of absorption and metabolism and the specificity of ABT. This method should have utility in drug discovery for the identification of factors limiting oral bioavailability. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:1334,1341, 2006 [source]

,-cyclodextrin reduces bioavailability of orally administered [3H]benzo[a]pyrene in the rat

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2005
Goran Westerberg
Abstract The excretion and plasma kinetics of total radioactivity were studied following single oral administration of [3H]benzo[a]pyrene after multiple oral administration of ,-cyclodextrin at 0, 5, 50, or 500 mg/kg/day. The AUC and Cmax values in male and female rats following administration of [3H]benzo[a]pyrene in combination with 5 to 500 mg/kg ,-cyclodextrin were considerably lower than that in rats administered [3H]benzo[a]pyrene alone. At all dose levels of ,-cyclodextrin, the excretion of total radioactivity was almost entirely via feces, with <2% recovered in urine, demonstrating either that absorption of the orally administered dose was low or that, for any absorbed material, biliary excretion was the main route of excretion. However, following administration of vehicle, up to 5% of the administered radioactivity was recovered in the urine, suggesting that absorption may have been reduced by the presence of ,-cyclodextrin in the intestine. At all dose levels of ,-cyclodextrin, there was minimal retention of radioactivity in the carcase at the end of the collection period. ,-Cyclodextrin did not affect the apparent terminal half-life of radioactivity. Therefore, the reduced systemic exposure of rats to radioactivity in the presence of ,-cyclodextrin is likely related to a reduced oral bioavailability. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:114,119, 2005 [source]

Pharmacokinetic aspects of biotechnology products

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2004
Lisa Tang
Abstract In recent years, biotechnologically derived peptide and protein-based drugs have developed into mainstream therapeutic agents. Peptide and protein drugs now constitute a substantial portion of the compounds under preclinical and clinical development in the global pharmaceutical industry. Pharmacokinetic and exposure/response evaluations for peptide and protein therapeutics are frequently complicated by their similarity to endogenous peptides and proteins as well as protein nutrients. The first challenge frequently comes from a lack of sophistication in various analytical techniques for the quantification of peptide and protein drugs in biological matrices. However, advancements in bioassays and immunoassays,along with a newer generation of mass spectrometry-based techniques,can often provide capabilities for both efficient and reliable detection. Selection of the most appropriate route of administration for biotech drugs requires comprehensive knowledge of their absorption characteristics beyond physicochemical properties, including chemical and metabolic stability at the absorption site, immunoreactivity, passage through biomembranes, and active uptake and exsorption processes. Various distribution properties dictate whether peptide and protein therapeutics can reach optimum target site exposure to exert the intended pharmacological response. This poses a potential problem, especially for large protein drugs, with their typically limited distribution space. Binding phenomena and receptor-mediated cellular uptake may further complicate this issue. Elimination processes,a critical determinant for the drug's systemic exposure,may follow a combination of numerous pathways, including renal and hepatic metabolism routes as well as generalized proteolysis and receptor-mediated endocytosis. Pharmacokinetic/pharmacodynamic (PK/PD) correlations for peptide and protein-based drugs are frequently convoluted by their close interaction with endogenous substances and physiologic regulatory feedback mechanisms. Extensive use of pharmacokinetic and exposure/response concepts in all phases of drug development has in the past been identified as a crucial factor for the success of a scientifically driven, evidence-based, and thus accelerated drug development process. Thus, PK/PD concepts are likely to continue and expand their role as a fundamental factor in the successful development of biotechnologically derived drug products in the future. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:2184,2204, 2004 [source]

Application of pharmacokinetic,pharmacodynamic modeling to predict the kinetic and dynamic effects of anti-methotrexate antibodies in mice

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2003
Evelyn D. Lobo
Abstract We have shown that intravenous (iv) administration of anti-methotrexate (MTX) antibodies (AMAb) reduces the systemic exposure of intraperitoneal (ip) MTX therapy, and we have proposed that AMAb effects on MTX systemic exposure would allow a reduction in MTX-induced systemic toxicity (i.e., producing a desirable antagonistic effect). However, many literature reports have shown that anti-toxin antibodies occasionally demonstrate unexpected agonist-like activity, increasing the extent of toxicity induced by their ligand. In this report, we have utilized a pharmacokinetic,pharmacodynamic (PKPD) model to predict the potential of AMAb to increase or decrease the magnitude of MTX-induced body weight loss in mice. Simulations predicted that both anti-MTX immunoglobulin G (AMI) and anti-MTX Fab fragments (AMF) would lead to increases or decreases in MTX toxicity, with effects dependent on the dosing protocol used. Based on the computer simulations, two protocols were selected for in vivo evaluation of predicted agonistic or antagonistic effects. Murine monoclonal AMI and AMF were produced, purified, and characterized. Agonistic effects were tested after 24-h infusion of ip MTX (10 mg/kg) and iv administration of an equimolar dose of AMI. Antagonistic effects were tested after 72-h infusion of ip MTX (5 mg/kg) and iv infusion of an equimolar dose of AMF. Consistent with model predictions of agonist-like activity, the 24-h AMI protocol led to significantly increased animal mortality (all animals died, p,<,0.005) and mean nadir weight loss (p,<,0.005). Also consistent with the predictions of the PKPD model, the 72-h AMF protocol significantly decreased animal mortality and mean nadir body weight loss (p,<,0.01). Thus, these studies demonstrate that agonistic and antagonistic effects of anti-toxin antibodies may be predicted through the use of an integrated PKPD model. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1665,1676, 2003 [source]

Rapid absorption of sumatriptan powder and effects on glyceryl trinitrate model of headache following intranasal delivery using a novel bi-directional device

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 9 2009
Dr Remy Luthringer
Abstract Objectives The aim was to investigate the pharmacokinetics of intranasal sumatriptan (administered using a novel bi-directional powder delivery device) and study its effects on quantitative electroencephalography in patients with migraine. The safety profiles of the two formulations were also compared. Methods The pharmacokinetics of intranasal sumatriptan (10 mg and 20 mg) administered using a novel breath-actuated bi-directional powder delivery device were compared with subcutaneous sumatriptan (6 mg), along with an investigation of their effects on the electroencephalogram (EEG) following glyceryl trinitrate (GTN) challenge in 12 patients with migraine using a randomized, three-way cross-over design. Key findings Following intranasal delivery, median tmax was 20 min with both doses compared with 10 min after the subcutaneous dose. Mean ± SD values for Cmax were 96 ± 25, 11 ± 7 and 16 ± 6 ng/ml for subcutaneous, intranasal 10 mg and intranasal 20 mg formulations, respectively. Values for area under the curve were also lower with the intranasal doses. Intranasal and subcutaneous sumatriptan induced similar EEG changes characterized by reduced theta-power and increased beta-power. The majority of study participants were free of pain according to the headache severity score with all treatments from 15 min through to 8 h post-dose. All treatments were well tolerated and there were no reports of bitter aftertaste after intranasal delivery. Sumatriptan was rapidly absorbed after intranasal administration using the new device. Using the GTN challenge, sumatriptan powder delivered intranasally at a dose of 20 mg by the new device had effects similar to those of subcutaneous sumatriptan on EEG and reported headache pain, despite much lower systemic exposure. Conclusions Administration of sumatriptan intranasally at doses of 10 mg and 20 mg by the breath actuated bi-directional powder delivery device results in rapid absorption. Delivery to target sites beyond the nasal valve induced a similar EEG profile to subcutaneous sumatriptan 6 mg and prevented migraine attacks in patients following GTN challenge. Intranasal administration of sumatriptan powder with the breath actuated bi-directional powder delivery device was well tolerated. [source]

Effects of non-steroidal anti-inflammatory drugs on the pharmacokinetics and elimination of aciclovir in rats

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 3 2005
Hye-Sun Gwak
This study aims to investigate the effect of commonly used non-steroidal anti-inflammatory drugs (NSAIDs) on the pharmacokinetics and the renal elimination of aciclovir in rats. Pharmacokinetic parameters were determined following an intravenous administration of aciclovir (5 mg kg,1) to rats in the presence and absence of ketoprofen or naproxen (25 mg kg,1). Compared with the control (given aciclovir alone), pre-treatment with ketoprofen or naproxen 30 min before aciclovir administration significantly altered the pharmacokinetics of aciclovir. Renal clearance of aciclovir was reduced by approximately two fold in the presence of ketoprofen or naproxen. Consequently, the systemic exposure (AUC) to aciclovir in the rats pre-treated with ketoprofen or naproxen was significantly (P < 0.05) higher than that from the control group given aciclovir alone. Furthermore, the mean terminal plasma half-life of aciclovir was enhanced by 4,5 fold by pre-treatment with ketoprofen or naproxen. These results suggest that NSAIDs, such as ketoprofen and naproxen, are effective in altering the pharmacokinetics of aciclovir by inhibiting the organic anion transporter-mediated tubular secretion of aciclovir. Therefore, concomitant use of ketoprofen or naproxen with aciclovir should require close monitoring for clinical consequence of potential drug interaction. [source]

The effects of the phytoestrogenic isoflavone genistein on the hepatic disposition of preformed and hepatically generated gemfibrozil 1- O -acyl glucuronide in the isolated perfused rat liver

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 10 2003
Anthony N. Lucas
ABSTRACT Foods and complementary medicines contain phytoestrogenic isoflavones such as genistein, which undergo hepatic glucuronidation and excretion into bile and can potentially interfere with the hepatic elimination of other compounds. To investigate this potential, livers from Sprague-Dawley rats were perfused in single-pass mode with preformed gemfibrozil 1- O -acyl glucuronide (GG) (1 ,M, n = 12) for 60 min followed by a 30-min washout phase, or with gemfibrozil (1 ,M n = 10) for 120 min. Half of each group of livers were co-perfused with genistein (10 ,M) throughout the experiment. Perfusate and bile were analyzed for GG and gemfibrozil by HPLC. Co-perfusion with genistein significantly (P < 0.05) decreased the biliary extraction ratio of preformed GG from a mean of 0.82 to 0.65 and the first-order rate constant for transport of GG into bile from 0.054 + 0.010 to 0.032 + 0.008 min,1, but increased the first-order rate constant for sinusoidal efflux of GG from 0.128 + 0.023 to 0.227 + 0.078 min,1. Co-perfusion with genistein also significantly decreased the biliary extraction ratio of hepatically generated GG from 0.95 + 0.01 to 0.83 + 0.05. The findings confirm that genistein increases the potential for hepatic and systemic exposure to hepatically generated glucuronides, which may be important for patients on conventional drugs who consume isoflavones. [source]

Review article: 5-aminosalicylate formulations for the treatment of ulcerative colitis , methods of comparing release rates and delivery of 5-aminosalicylate to the colonic mucosa

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 6 2008
G. R. LICHTENSTEIN
Summary Background, Many oral 5-aminosalicylic acid (5-ASA) formulations are designed to maximize 5-ASA release in the colon where it acts topically on the colonic mucosa. Delayed-release formulations and azo-prodrugs minimize 5-ASA absorption in the upper gastrointestinal (GI) tract. Aims, To review methods for assessing 5-ASA release and colonic distribution from oral formulations, and the potential use of this information for guiding clinical decisions. Methods, PubMed and recent conference abstracts were searched for articles describing techniques used to assess 5-ASA release from ulcerative colitis (UC) therapies. Results, In-vitro GI models, although unable to simulate more complex aspects of GI physiology, can provide useful data on 5-ASA release kinetics and bioaccessibility. Gamma-scintigraphy is useful for investigating GI disintegration of different formulations, but may not accurately reflect 5-ASA distribution. Plasma pharmacokinetic studies provide data on systemic exposure, but not on colonic distribution or mucosal uptake. Mucosal biopsies provide direct evidence of colonic distribution and may predict clinical efficacy, but must be interpreted cautiously because of considerable inter-subject variability and other confounding factors. Conclusion, While assessment of 5-ASA release is important, limitations of individual measurement techniques mean that randomized clinical studies in UC patients remain the best guide for dosing and treatment regimen decisions. [source]

Individualized population pharmacokinetic model with limited sampling for cyclosporine monitoring after liver transplantation in clinical practice

ALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 10 2007
P. LANGERS
Summary Background, We recently developed and validated limited sampling models (LSMs) for cyclosporine monitoring after orthotopic liver transplantation based on individualized population pharmacokinetic models with Bayesian modelling. Aim, To evaluate LSM in practice, and to seek optimal balance between benefit and discomfort. Methods, In 30 stable patients, more than 6 months after orthotopic liver transplantation, previously switched from trough- to 2 h post-dose (C2)-monitoring, we switched to 3-monthly LSM 0,1,2,3 h-monitoring. During 18 months we evaluated dose, creatinine clearance, calculated area under the curve, intra-patient pharmacokinetic variability and ability to assess systemic exposure by several previously validated LSMs. Results, Within patients, there was variability of cyclosporine-area under the curve with the same dose (CV of 15%). Compared to C2-monitoring, there was no significant difference in dose (P = 0.237), creatinine clearance (P = 0.071) and number of rejections. Some models showed excellent correlation and precision with LSM 0,1,2,3 h comparing area under the curves (0,2 h: r2 = 0.88; 0,1,3 h: r2 = 0.91; 0,2,3 h: r2 = 0.92, all P < 0.001) with no difference in advised dose. Conclusions, The limited sampling model, with only trough- and 2-h sampling, yields excellent accuracy and assesses systemic exposure much better than C2 with less bias and greater precision. Considering the calculated intra-patient variability, more precision is redundant, so LSM 0,2 h seems the optimal way of cyclosporine-monitoring. [source]

Low Systemic Absorption and Good Tolerability of Pimecrolimus, Administered as 1% Cream (Elidel®) in Infants with Atopic Dermatitis , A Multicenter, 3-Week, Open-Label Study

PEDIATRIC DERMATOLOGY, Issue 5 2005
Doris Staab M.D.
Here we evaluate pimecrolimus blood concentrations and tolerability to pimecrolimus cream 1% in 22 infants below 2 years of age with atopic dermatitis (10,92% body surface area affected at baseline). Efficacy was assessed as a secondary objective. Pimecrolimus cream 1% was applied twice daily for 3 weeks. Blood concentrations were low, typically (96% of total 100 concentrations measured) below 2 ng/mL, the majority (71%) remaining below 0.5 ng/mL. The highest concentration observed was 2.26 ng/mL. At steady state, there was no indication of accumulation. Pimecrolimus was well tolerated locally and systemically, with no serious adverse events recorded. Most adverse events recorded (35 in 17/22 patients) were typical of the young pediatric population studied, of mild to moderate severity, and not considered to be study-medication related, with the exception of four local adverse effects limited to the site of cream application. No clinically relevant change was observed in physical examination, vital signs, or laboratory safety parameters. A rapid onset of therapeutic effect was observed within the first four days of treatment. Pimecrolimus cream 1% is well tolerated in infants 3 to 23 months of age treated for 3 weeks, and results in minimal systemic exposure. [source]

The science of aerosol delivery in cystic fibrosis

PEDIATRIC PULMONOLOGY, Issue S9 2008
David E. Geller MD
Abstract Aerosolized drugs are universally used for treatment of cystic fibrosis airway disease. Inhalation can increase topical efficacy and reduce systemic exposure and toxicity of many drugs. A wide variety of inhaled drugs already exist with many more in the therapeutic pipeline. Understanding the principles of aerosol delivery and how aerosol devices function is important in designing the best therapeutic regimens for CF patients. The variables that determine where an aerosol deposits are numerous and complex. Important aerosol-related variables include particle-size distribution, hygroscopic properties, viscosity and surface tension of the drug. Patient-related variables include inspired flow rate, tidal volume, respiratory rate, breath-holding, upper airway anatomy, lower airways obstruction, and the cognitive and physical ability to use the device. These factors vary widely between patients of different age groups and disease severities, and cause the high variability in drug delivery seen with aerosol drugs. Classic aerosol delivery devices like metered dose inhalers and dry-powder inhalers are small, portable, and have short treatment times. However, they are limited by small drug payloads and user technique problems. Jet nebulizers are commonly used for CF drugs, are easy to operate, require no special breathing pattern, and can deliver very large quantities of drug. However, they require a power or air source, cleaning and sanitizing, and are relatively time consuming. Recently, novel aerosol delivery systems and formulations have been developed to improve delivery efficiency and reduce variability and delivery time. These new systems can ease the treatment burden and improve adherence and outcomes in cystic fibrosis. Pediatr Pulmonol. 2008; 43:S5,S17. © 2008 Wiley-Liss, Inc. [source]

Novel tobramycin inhalation powder in cystic fibrosis subjects: Pharmacokinetics and safety

PEDIATRIC PULMONOLOGY, Issue 4 2007
David E. Geller MD
Abstract Aerosolized antibiotics are associated with a high treatment burden that can result in non-adherence to chronic therapy. We evaluated the pharmacokinetics (PK) and safety of tobramycin inhalation powder (TIP), a novel dry-powder formulation designed to deliver a high payload of tobramycin topically to the lungs for management of chronic Pseudomonas aeruginosa infections. This was a multi-center, open-label, sequential-cohort, single-dose, dose-escalation study using the standard 300 mg dose of tobramycin solution for inhalation (TSI) as an active control. Subjects were randomized to TIP or TSI in a 3:1 ratio in each of five cohorts. Measurements included serum and sputum tobramycin concentrations, administration time, serum chemistries, acute change in lung function, and adverse events (AEs). Out of 90 randomized subjects, 86 had data for safety analysis; and 84 had data for PK analysis. Serum tobramycin PK profiles were similar for TIP and TSI. Four capsules of 28 mg TIP (total tobramycin dose 112 mg) produced comparable systemic exposure to 300 mg TSI, in less than one-third the administration time. The most common AEs associated with TIP were cough (20%) and dysgeusia (17%). TIP allows for faster and more efficient pulmonary delivery of tobramycin than TSI and has a safety profile that supports continued clinical investigation. The increased rate of local respiratory tract irritation noted with TIP is not unexpected with a high-payload powder formulation. The development of dry powder inhaled antibiotics may represent an important advance in the treatment of chronic lung infections. Pediatr Pulmonol. 2007; 42:307,313. © 2007 Wiley-Liss, Inc. [source]

Muscle toxicity with statins,

PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 3 2010
Karin Hedenmalm MD
Abstract Purpose Statins rarely cause serious muscle toxicity and rhabdomyolysis. The aim of our investigation was to identify and quantify potential risk factors for statin-induced rhabdomyolysis. Methods All cases of suspected adverse reactions to statins reported to the Swedish Adverse Drug Reactions Advisory Committee until 15 September 2006 containing the codes myalgia, myopathy, increased serum creatine kinase (CK), myoglobinuria or rhabdomyolysis were included in the study. Cases were classified into different CK categories, where cases with CK levels >10 times the upper limit of normal (ULN) laboratory range were compared with cases with normal CK levels (in some analyses cases with CK not measured were also included as controls). Fisher's test and multiple logistic regression were used to test the degree of association. Results A total of 338 cases with muscle toxicity were identified. CK had not been measured in 148 cases. Of the remaining 190 cases, 59 were classified as rhabdomyolysis, 62 had CK increases below the level of rhabdomyolysis, 69 had normal CK and 2 contained insufficient information to classify the degree of CK increase. A high statin dose and concomitant interacting drug treatment were over-represented among cases with rhabdomyolysis compared with cases with normal CK. Renal disease and unusual strenuous muscular activity were also associated with an increased risk of rhabdomyolysis when the control group included cases with CK not measured. Conclusion Results from our study support previous studies indicating that the risk of rhabdomyolysis with statin treatment increases with increase in systemic exposure to the statin. Renal disease and unusual strenuous muscular activity may also contribute to an increased risk of rhabdomyolysis. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Development of a cytokine analog with enhanced stability using computational ultrahigh throughput screening

PROTEIN SCIENCE, Issue 5 2002
Peizhi Luo
Abstract Granulocyte-colony stimulating factor (G-CSF) is used worldwide to prevent neutropenia caused by high-dose chemotherapy. It has limited stability, strict formulation and storage requirements, and because of poor oral absorption must be administered by injection (typically daily). Thus, there is significant interest in developing analogs with improved pharmacological properties. We used our ultrahigh throughput computational screening method to improve the physicochemical characteristics of G-CSF. Improving these properties can make a molecule more robust, enhance its shelf life, or make it more amenable to alternate delivery systems and formulations. It can also affect clinically important features such as pharmacokinetics. Residues in the buried core were selected for optimization to minimize changes to the surface, thereby maintaining the active site and limiting the designed protein's potential for antigenicity. Using a structure that was homology modeled from bovine G-CSF, core designs of 25,34 residues were completed, corresponding to 1021,1028 sequences screened. The optimal sequence from each design was selected for biophysical characterization and experimental testing; each had 10,14 mutations. The designed proteins showed enhanced thermal stabilities of up to 13°C, displayed five-to 10-fold improvements in shelf life, and were biologically active in cell proliferation assays and in a neutropenic mouse model. Pharmacokinetic studies in monkeys showed that subcutaneous injection of the designed analogs results in greater systemic exposure, probably attributable to improved absorption from the subcutaneous compartment. These results show that our computational method can be used to develop improved pharmaceuticals and illustrate its utility as a powerful protein design tool. [source]

Blood concentrations, tolerability and efficacy of pimecrolimus cream 1% in Japanese infants and children with atopic dermatitis

THE JOURNAL OF DERMATOLOGY, Issue 4 2007
Lawrence F. EICHENFIELD
ABSTRACT Pimecrolimus cream 1% is a topical calcineurin inhibitor for the treatment of atopic dermatitis. Minimal systemic exposure to pimecrolimus has been previously observed in Caucasian pediatric patients treated with the cream twice daily for up to 1 year. The objective of this open-label, non-comparative, multicenter study was to assess the systemic exposure, tolerability and efficacy of pimecrolimus cream 1% when used twice daily for 3 weeks in pediatric patients of Japanese background. The patient cohort consisted of 17 Japanese infants and children (age range, 3.6 months to 11.6 years) with atopic dermatitis of at least mild severity affecting ,10% of the total body surface area (range, 10,48%). Pimecrolimus cream 1% was applied twice daily for 3 weeks. Blood levels of pimecrolimus were determined on days 1, 10 and 22. Safety and tolerability were evaluated by monitoring adverse events, laboratory parameters, physical condition and vital signs. Efficacy parameters included the Eczema Area and Severity Index, the Investigators' Global Assessment and the pruritus score. The median exposure to pimecrolimus cream 1% was 22 treatment days (range, 9,29 treatment days). Pimecrolimus blood concentrations were <0.5 ng/mL in 94% of samples on day 1, in 93% of samples on day 10 and in 100% of samples on day 22, with no indication of an increase with increasing body surface area treated (up to 48% of the total body surface area). No drug-related systemic adverse events or serious adverse events were reported. Treatment was effective according to all efficacy parameters. The findings of this study indicate that the use of pimecrolimus cream 1% results in minimal systemic absorption of the active ingredient in pediatric patients of Japanese background with extensive disease. [source]

Pharmacokinetics for Once- Versus Twice-Daily Tacrolimus Formulations in De Novo Kidney Transplantation: A Randomized, Open-Label Trial

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 11 2009
Z. Wlodarczyk
Tacrolimus, a cornerstone immunosuppressant, is widely available as a twice-daily formulation (Tacrolimus BID). A once-daily prolonged-release formulation (Tacrolimus QD) has been developed that may improve adherence and impart long-lasting graft protection. This study compared the pharmacokinetics (PK) of tacrolimus in de novo kidney transplant patients treated with Tacrolimus QD or Tacrolimus BID. A 6-week, open-label, randomized comparative study was conducted in centers in Europe and Australia. Eligible patients received Tacrolimus QD or Tacrolimus BID. PK profiles were obtained following the first tacrolimus dose (day 1), and twice under steady-state conditions. As secondary objectives, efficacy and safety parameters were also evaluated. Sixty-six patients completed all PK profiles (34 Tacrolimus QD, 32 Tacrolimus BID). Mean AUC0,24 of tacrolimus on day 1 was approximately 30% lower for Tacrolimus QD than Tacrolimus BID (232 and 361 ng.h/mL, respectively), but was comparable by day 4. There was a good correlation and a similar relationship between AUC0,24 and Cmin for both formulations. Efficacy and safety data were also comparable over the 6-week period. Tacrolimus QD can be administered once daily in the morning on the basis of the same systemic exposure and therapeutic drug monitoring concept as Tacrolimus BID. [source]