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Mean AUC (mean + auc)
Selected AbstractsCardiovascular Actions of Orexin-A in the Rat Subfornical OrganJOURNAL OF NEUROENDOCRINOLOGY, Issue 1 2007P. M. Smith Orexin-A is a neuropeptide, primarily produced in the lateral hypothalamic/perifornical hypothalamus. Orexin receptors and immunoreactive neuronal fibres are widely distributed throughout the brain, suggesting integrative neurotransmitter roles in a variety of physiological systems. Intracerebroventricular injections of orexin-A increase blood pressure and stimulate drinking, and the subfornical organ (SFO), a circumventricular structure implicated in autonomic control, is a potential site at which orexin may act to exert these effects. We have therefore used microinjection techniques to examine the effects of orexin-A administered directly into the SFO on blood pressure and heart rate in urethane anaesthetised male Sprague-Dawley rats. Orexin-A microinjection (50 fmol) into the SFO caused site-specific decreases in blood pressure (SFO: mean area under curve (AUC) = ,681.7 ± 46.8 mmHg*s, n = 22 versus non-SFO: 63.68 ± 54.69 mmHg*s, n = 15, P < 0.001), and heart rate (SFO: mean AUC = ,26.7 ± 2.8 beats, n = 22, versus non-SFO: mean AUC = 1.62 ± 2.1 beats, n = 15, P < 0.001). Vagotomy did not alter the hypotensive or bradycardic responses elicited by orexin-A microinjection. Prior ,-adrenoceptor blockade with phenoxybenzamine (1 mg/kg, i.v.) masked the orexin-A induced blood pressure (mean AUC = ,122.6 ± 17.6 mmHg*s, n = 4, P < 0.01 paired t-test) and heart rate (mean AUC = ,6.7 ± 1.7 beats, n = 4, P < 0.05, paired test) response. The orexin-A induced heart rate response was attenuated when ,-adrenoceptors were blocked with propranolol (1 mg/kg, i.v.; mean AUC = 0.6 ± 2.8 beats, n = 5, P < 0.01 paired t-test). These studies demonstrate that microinjection of orexin-A into the SFO causes site specific decreases in blood pressure and heart rate which is mediated by a reduction in sympathetic tone. [source] Interconversion pharmacokinetics of eplerenone, a selective aldosterone blocker, and its lactone-ring open formJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2002Chyung S. Cook Abstract The interconversion pharmacokinetics of eplerenone and its lactone-ring open form, SC-70303, were examined in dogs using a stable isotope method. [13CD3]EP and SC-70303 were coadministered orally (10 mg/kg) and intravenously (5 mg/kg) as aqueous solutions under fasted conditions. After I.V. administration of [13CD3]EP, the mean AUC of [13CD3]EP was 16.0 h,·,,g/mL, while the Cmax, Tmax, and AUC for [13CD3]SC-70303 acid were 0.744 ,g/mL, 0.5 h, and 3.49 h,·,,g/mL, respectively. After I.V. administration of SC-70303, the AUC for SC-70303 acid was 6.36 h,·,,g/mL, while the Cmax, Tmax, and AUC for EP were 2.26 ,g/mL, 0.5 h, and 9.48 h,·,,g/mL, respectively. After oral administration of [13CD3]EP, the Cmax, Tmax, and AUC for [13CD3]EP were 6.01 ,g/mL, 0.5 h, and 27.7 h,·,,g/mL, respectively, and the corresponding values for [13CD3]SC-70303 acid were 0.972 ,g/mL, 0.75 h, and 5.52 h,·,,g/mL, respectively. After oral administration of SC-70303, the Cmax, Tmax, and AUC for EP were 1.38 ,g/mL, 0.83 h, and 9.29 h,·,,g/mL, respectively, and the corresponding values for SC-70303 acid were 0.330 ,g/mL, 0.67 h, and 2.19 h,·,,g/mL, respectively. The systemic availability was 90% for [13CD3]EP and 17.5% for SC-70303 acid. EP and SC-70303 acid were rapidly interconvertible in the dog. The percentage of dose converted to [13CD3]SC-70303 acid following I.V. administration of [13CD3]EP was 55.0%, while the percentage of dose converted to EP following I.V. administration of SC-70303 was 60.2%. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:1383,1389, 2002 [source] Pharmacokinetics of ceftiofur in red deer (Cervus elaphus)JOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 1 2004Mark L. Drew Twelve adult female red deer (Cervus elaphus) were given 250 mg of ceftiofur sodium by intramuscular injection (i.m.) and ballistic implant in a crossover design. Blood samples were taken from an in-dwelling jugular catheter prior to drug administration and at 0.25, 0.5, 1, 2, 4, 8, 12, 24, 36, 48, and 72 h postadministration of the drug. Samples were centrifuged and plasma kept frozen at ,70 °C until analysis for ceftiofur and active metabolites using an HPLC method. The pharmacokinetics of ceftiofur and metabolites after i.m. dosing and following ballistic implant were quite different. Absorption after i.m. injection was rapid; whereas following ballistic implant there was a lag-time until concentrations were detectable in plasma. The maximum concentration reached in plasma was higher following injection compared with ballistic implant, however the AUC calculated after ballistic implant was almost identical to the mean AUC found after i.m. dosing. The results indicate that i.m. administration of ceftiofur maintains adequate plasma levels for most susceptible bacterial pathogens for at least 12 h; therefore twice daily administration is needed in red deer. Ballistic implants produced plasma concentrations above the MIC for most bacterial pathogens from 4 to 24 h in most animals after administration; however, absorption of the drug was variable and some did not maintain effective concentrations for more than a few hours. Ceftiofur is a useful drug in red deer and twice daily i.m. administration dosing should allow treatment for susceptible bacterial pathogens. [source] Pharmacokinetics of nifedipine in TaiwaneseBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 2 2004Shu-Chen Chien Abstract To elucidate the pharmacokinetics of nifedipine in Taiwanese, a retrospective review of nifedipine bioequivalence studies completed in Taiwan in the past 5 years was conducted. A total of 198 healthy male volunteers were given a single dose of a 10 mg Adalat® capsule as a reference drug after overnight fasting. Pharmacokinetic parameters derived from Adalat® administration were calculated by non-compartmental analysis with the WinNonlin program. After oral administration of an immediate-release dosage form of a 10 mg nifedipine capsule to Taiwan residents, a skewed distribution with no clear evidence of bimodality of pharmacokinetic parameters was observed. The mean Cmax was 143.12±53.48 ng/ml, the mean AUC was 293.77±115.62 ng·h/ml, the mean T1/2 was 3.08±1.61 h, and the median value of Tmax was 0.61 h. Compared with other published studies, the Cmax and AUC of nifedipine after 10 mg administration were significantly higher in Taiwanese than in British and American subjects. However, the Cmax and AUC were similar to those of Indian and Mexican subjects. According to the antimode of AUC distribution of 22.5 ng·h/ml/mg proposed by Kleinbloesem, 69.7% of Taiwanese can be categorized as slow metabolizers. Based on the results in this study, the majority of Taiwanese show lower activity of nifedipine metabolism. Copyright © 2004 John Wiley & Sons, Ltd. [source] Influence of methotrexate exposure on outcome in patients treated with MBVP chemotherapy for primary central nervous system lymphomaBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 3 2010Hélčne Blasco WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT Although treated using the same high-dose methotrexate (HD-MTX)-based multiagent chemotherapy, patients with primary central nervous system lymphoma (PCNSL) have significant differences in outcome. However, little information has been published about factors influencing outcome in PCNSL. As it is known that the pharmacokinetics of MTX vary considerably between subjects leading to different exposure in patients receiving the same dose, it is important to evaluate its role in response to chemotherapy. WHAT THIS STUDY ADDS This study is the first to evaluate the exposure,response relationship in patients treated with MBVP chemotherapy. We found that patients who were early non-responders to MBVP chemotherapy had poor survival, whatever the salvage regimen. Tumour response at early evaluation was not associated with MTX pharmacokinetics and increasing the dose would probably not improve results. AIMS Although the standard treatment for primary central nervous system lymphoma (PCNSL) consists of three cycles of MBVP (methotrexate, BCNU, VP16, methylprednisolone) and radiotherapy, early failure of treatment may require modification of the treatment. However, our understanding of the outcome in such patients and of the factors involved in early failure of treatment is poor. In addition to known prognostic factors, we evaluated the influence of methotrexate (MTX) exposure on the response to MBVP chemotherapy in patients treated for PCNSL after the first two cycles. METHODS We retrospectively analyzed all patients with PCNSL treated with the MBVP regimen over the previous 10 years. Clinical, personal data and known prognostic factors were studied. The parameters of MTX exposure were estimated using a population pharmacokinetic approach with NONMEM. Objective response (OR), overall survival (OS) and failure-free survival (FFS) were evaluated in all patients. RESULTS Thirty-seven patients were studied. We observed lower FFS and OS (0.49 years) in patients who were not able to receive the planned treatment (group 1, n= 12) than in those who received three cycles (8.04 years) (group 2, n= 25). Known prognostic factors were comparable in both groups, but mean dose of MTX and mean AUC tended to be lower in patients who failed prematurely or showed no response after two cycles. CONCLUSIONS We found that patients who were early non-responders to MBVP chemotherapy had poor survival, without major influence of MTX exposure. It is thus probably unlikely that increasing the dose of MTX would improve outcome. [source] Exposure to oral oxycodone is increased by concomitant inhibition of CYP2D6 and 3A4 pathways, but not by inhibition of CYP2D6 aloneBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 1 2010Juha Grönlund WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT , Oxycodone is an opioid analgesic that is metabolized mainly in the liver by cytochrome P450 (CYP) 2D6 and 3A4 enzymes. , So far, the effects of CYP2D6 or CYP3A4 inhibitors on the pharmacokinetics of oxycodone in humans have not been systematically studied. WHAT THIS STUDY ADDS , Drug interactions arising from CYP2D6 inhibition most likely have minor clinical importance for oral oxycodone. , When both of CYP2D6 and CYP3A4 pathways are inhibited, the exposure to oral oxycodone is increased substantially. AIM The aim of this study was to find out whether the inhibition of cytochrome P450 2D6 (CYP2D6) with paroxetine or concomitant inhibition of CYP2D6 and CYP3A4 with paroxetine and itraconazole, altered the pharmacokinetics and pharmacological response of orally administered oxycodone. METHODS A randomized placebo-controlled cross-over study design with three phases was used. Eleven healthy subjects ingested 10 mg of oral immediate release oxycodone on the fourth day of pre-treatment with either placebo, paroxetine (20 mg once daily) or paroxetine (20 mg once daily) and itraconazole (200 mg once daily) for 5 days. The plasma concentrations of oxycodone and its oxidative metabolites were measured for 48 h, and pharmacological (analgesic and behavioural) effects were evaluated. RESULTS Paroxetine alone reduced the area under concentration,time curve (AUC(0,0,48 h)) of the CYP2D6 dependent metabolite oxymorphone by 44% (P < 0.05), but had no significant effects on the plasma concentrations of oxycodone or its pharmacological effects when compared with the placebo phase. When both oxidative pathways of the metabolism of oxycodone were inhibited with paroxetine and itraconazole, the mean AUC(0,,) of oxycodone increased by 2.9-fold (P < 0.001), and its Cmax by 1.8-fold (P < 0.001). Visual analogue scores for subjective drug effects, drowsiness and deterioration of performance were slightly increased (P < 0.05) after paroxetine + itraconazole pre-treatment when compared with placebo. CONCLUSIONS Drug interactions arising from CYP2D6 inhibition most likely have minor clinical importance for oral oxycodone if the function of the CYP3A4 pathway is normal. When both CYP2D6 and CYP3A4 pathways are inhibited, the exposure to oral oxycodone is increased substantially. [source] Influence of CYP2C19 polymorphism on the pharmacokinetics of nelfinavir and its active metaboliteBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 5 2009Bharat D. Damle WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT , The true influence of CYP2C19*2 mutation on the pharmacokinetics of nelfinavir and its active metabolite, M8, is not clear. , Often, published studies have combined *2 hetero- and homozygous poor metabolizers (PMs) and/or have very limited data from *2 homozygotes, which contributes to the lack of clarity. WHAT THIS STUDY ADDS , The pharmacokinetics of nelfinavir was delineated using pharmacogenomic data from 66 healthy subjects. , The exposure of nelfinavir was elevated, whereas that of M8 was reduced, in heterozygous and homozygous PMs in an incremental manner consistent with the loss of functional alleles. , However, the exposure of active moiety was only modestly elevated in hetero- and homozygous PMs. AIMS This study reports the pharmacokinetics of nelfinavir, its active metabolite, M8, and active moiety (nelfinavir + M8) in volunteers genotyped for CYP2C19 as extensive metabolizer (*1*1; n = 38), heterozygous poor metabolizer (PM) (*1*2; n = 22) and homozygous PM (*2*2; n = 6). METHODS Subjects received nelfinavir at normal dose (3.5 days of 1250 mg q12h) or high dose (1250 mg q12h for 3 days and single dose of 3125 mg on day 4). Steady-state plasma samples were analysed by high-performance liquid chromatography/ultraviolet assay to determine pharmacokinetics. RESULTS At steady state, the mean Cmax was 42% [95% confidence interval (CI) 19, 69] and 63% (95% CI 20, 122) higher, and mean AUC was 51% (95% CI 24, 83) and 85% (95% CI 32, 159) higher for *1*2 and *2*2 compared with *1*1 subjects, respectively. For M8, the mean Cmax and AUC were 35% (95% CI 6, 55) and 33% (95% CI ,3, 56), respectively, lower for *1*2 compared with *1*1 subjects. M8 was not detectable in *2*2 subjects. The mean Cmax and AUC values for the active moiety were higher by 30,35% for the *1*2 and *2*2 compared with *1*1 subjects. CONCLUSIONS Mutation in CYP2C19 increased the systemic exposure of nelfinavir and reduced the exposure of M8. No significant differences were noted among the heterozygous (*1*2) and homozygous (*2*2) PMs. These changes are not considered to be clinically relevant and hence the use of nelfinavir does not require prior assessment of CYP2C19 genotype. [source] Pharmacokinetics, safety, and efficacy of mycophenolate mofetil in combination with sirolimus or ciclosporin in renal transplant patientsBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 6 2007Mark D. Pescovitz Aims To compare the pharmacokinetics of mycophenolic acid (MPA) and its metabolite (MPAG) when mycophenolate mofetil (MMF) is administered in combination with sirolimus or ciclosporin (CsA) in renal allograft recipients. Safety and efficacy (biopsy-proven acute rejection (BPAR)) were also assessed. Methods Patients (n = 45) were randomized 2 : 1 to receive treatment with sirolimus (n = 30; dosed to maintain trough concentrations of 10,25 ng ml,1 until week 8, and then 8,15 ng ml,1 thereafter) or CsA (n = 15; administered as per centre practice) both in combination with daclizumab, oral MMF and corticosteroids. Pharmacokinetic assessments were performed at day 7, week 4, and months 3 and 6 post-transplant. The primary endpoint was the AUC(0,12 h) for MPA and MPAG. The pharmacokinetics of sirolimus were also assessed. Results MPA exposure was 39,50% lower (month 6 mean AUC(0,12 h) (95%CI): 40.4 (33.8, 47.0) vs. 68.5 (54.9, 82.0) µg ml,1 h) and MPAG exposure was 25,52% higher (722 (607, 838) vs. 485 (402, 569) µg ml,1 h at month 6) in the presence of CsA compared with sirolimus across visits. BPAR was 40.0% with sirolimus and 13.3% with CsA. The incidence of hypertension, tremors and hirsutism was higher with CsA than with sirolimus, while the incidence of diarrhoea, hyperlipidaemia and impaired wound closure was higher with sirolimus. No deaths, malignancies or graft losses were reported. Conclusions Co-administration of sirolimus with MMF led to greater MPA exposure, but lower MPAG exposure, than co-administration with CsA. As rejection rates were higher in the absence of CsA, further study of calcineurin inhibitor-free regimens is required before general recommendations can be made. [source] Effect of an oral contraceptive preparation containing ethinylestradiol and gestodene on CYP3A4 activity as measured by midazolam 1,-hydroxylationBRITISH JOURNAL OF CLINICAL PHARMACOLOGY, Issue 4 2000Sanna Palovaara Aims,To characterize the effect of an oral contraceptive (OC) containing ethinylestradiol and gestodene on the activity of CYP3A4 in vivo as measured by the 1,-hydroxylation of midazolam. Methods,In this randomised, double-blind, cross-over trial nine healthy female subjects received either a combined OC (30 µg ethinylestradiol and 75 µg gestodene) or placebo once daily for 10 days. On day 10, a single 7.5 mg dose of midazolam was given orally. Plasma concentrations of midazolam and 1,-hydroxymidazolam were determined up to 24 h and the effects of midazolam were measured with three psychomotor tests up to 8 h. Results,The combined OC increased the mean AUC of midazolam by 21% (95% CI 2% to 40%; P = 0.03) and decreased that of 1,-hydroxymidazolam by 25% (95% CI 10% to 41%; P = 0.01), compared with placebo. The metabolic ratio (AUC of 1,-hydroxymidazolam/AUC of midazolam) was 36% smaller (95% CI 19% to 53%; P = 0.01) in the OC phase than in the placebo phase. There were no significant differences in the Cmax, tmax, t˝ or effects of midazolam between the phases. Conclusions,A combined OC preparation caused a modest reduction in the activity of CYP3A4, as measured by the 1,-hydroxylation of midazolam, and slightly increased the AUC of oral midazolam. This study suggests that, at the doses used, ethinylestradiol and gestodene have a relatively small effect on CYP3A4 activity in vivo. [source] | ||||||||||