Oral Availability (oral + availability)

Distribution by Scientific Domains

Selected Abstracts

Bioavailability and efficacy of antisense morpholino oligomers targeted to c- myc and cytochrome P-450 3A2 following oral administration in rats

Vikram Arora
Abstract Antisense phosphorodiamidate Morpholino oligomers (PMO) are resistant to degradation by cellular hydrolases, DNases, RNases, and phosphodiesterases, but remain sensitive to prolonged exposure to low pH. The present studies evaluate the oral fractional bioavailability, stability, and efficacy of two distinct PMO sequences targeted to c- myc and cytochrome P-450 (CYP) 3A2. The c- myc antisense 20-mer, AVI-4126 (5,-ACGTTGAGGGGCATCGTCGC-3,), slowed the regenerative process in the rat liver after a 70% partial hepatectomy (PH). Rats were administered 3.0 mg/kg AVI-4126 in 0.1 mL saline via a bolus intravenous injection or in 0.5 mL sterile phosphate-buffered saline via gavage immediately following PH. The areas under the plasma concentration versus time curves revealed a fractional oral availability of 78.8% over a period of 10 min through 24 h. Immunoblot analysis of liver tissue from rats treated orally with AVI-4126 demonstrated a sequence-specific reduction in the target protein c-Myc, as well as secondary proliferation markers: proliferating cell nuclear antigen (PCNA), cyclin D1, and p53. The CYP3A2 antisense 22-mer AVI-4472 (5,-GAGCTGAAAGCAGGTCCATCCC-3,) caused a sequence-dependent reduction of approximately five-fold in the rat liver CYP3A2 protein levels and erythromycin demethylation activity in 24 h following oral administration at a dose of 2 mg/kg. It is concluded that oral administration of PMOs can inhibit c- myc and CYP3A2 gene expression in rat liver by an antisense-based mechanism of action. These studies highlight the potential for development of PMOs as orally administered therapeutic agents. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:1009,1018, 2002 [source]

Pharmacokinetics of sulfadimethoxine and ormetoprim in a 5:1 ratio following intraperitoneal and oral administration, in the hybrid striped bass (Morone chrysops × Morone saxitalis)

R. S. Bakal
Selected pharmacokinetic parameters for sulfadimethoxine and ormetoprim, administered in a 5:1 ratio, via the oral and intraperitoneal (i.p.) routes were determined in the hybrid striped bass (Morone chrysops × Morone saxitalis). Plasma concentrations of both drugs were determined by high-performance liquid chromatography. A first-order one-compartment model adequately described plasma drug disposition. The elimination half-lives for sulfadimethoxine following i.p. and oral administration were 26 and 10.5 h, respectively. The half-lives for ormetoprim administered via i.p. and oral routes were 7.5 and 3.9 h, respectively. Cmax for sulfadimethoxine via the i.p. and oral routes were calculated to be 27.7 (±9.0) ,g/mL at 3.6 h and 3.2 (±1.2) ,g/mL at 1.2 h, respectively. Cmax for ormetoprim via the i.p. route was calculated to be 1.2 (±0.5) ,g/mL at 9.1 h and 1.58 (±0.7) ,g/mL at 5.7 h for the oral route. The oral availability of sulfadimethoxine relative to the i.p. route was 4.6%, while the oral availability of ormetoprim relative to the i.p. route was 78.5%. Due to the nonconstant ratio of these drugs in the plasma of the animal, the actual drug ratio to use for determining minimum inhibitory concentration (MIC) is unclear. Using the ratio of the total amount of each drug that is absorbed as a surrogate for the mean actual ratio may be the best alternative to current methods. Using this ratio as determined in these studies, (2.14:1 sulfadimethoxine:ormetoprim) to determine the MICs the single 50 mg/kg oral dose of the 5:1 combination of sulfadimethoxine and ormetoprim appears to provide plasma concentrations high enough to inhibit the growth of Yersinia ruckeri, Edwardsiella tarda, and Escherichia coli. [source]

Validation of Microdialysis Sampling for Oral Availability Studies by Means of a New Ganciclovir Prodrug

Karin Lindén
Three different techniques were used in the study; microdialysis, blood and urinesampling. The oral uptake (11±2%) and the urinary recovery (106±5%) were determined. Animals given ganciclovir subcutaneously were subject either to microdialysis and blood sampling or to microdialysis alone. There was no significant difference between microdialysis and blood sampling in terms of blood concentration data, CL, Vd, half-life or AUC by means of Student's t-test. The oral bioavailability of the prodrug was 40±7% estimated from microdialysis sampling data and 48±4% estimated from urine sampling data. It is concluded that microdialysis is a valid method to use in pharmacokinetic studies of oral availability as well as for basic pharmacokinetic parameter estimation. [source]

ADME Investigations of Unnatural Peptides: Distribution of a 14C-Labeled ,,3 -Octaarginine in Rats

Markus Weiss
Abstract The highly positively charged, cell-penetrating ,,3 -octaarginine has been prepared with a radioactive label by acetylation at the N-terminus with a doubly 14C-labeled acetyl group (14CH314CO). With the radioactive compound, an ADME study (Absorption, Distribution, Metabolism, Excretion) was performed in male rats following an intravenous or oral dose of 1,mg/kg. Sampling was carried out after periods ranging from 5,min to 4,d or 7,d for blood/excretia and quantitative whole-body autoradioluminography (QWBA), respectively. After p.o. dosing, no systemic exposure to peptide-related radioactivity was observed, and the dose was completely excreted in the feces within 24,h suggesting the absence of relevant absorption; less than 3% of the i.v. dose was excreted from the animals within 4,d. Blood levels, after i.v. dosing, dropped within 4,d to less than 2% of Cmax and decreased afterwards only very slowly. No metabolites were observed in the systemic circulation. QWBA Data indicated that the distribution of the acetyl- , -octaarginine-related radioactivity in the organs and tissues shifted over time. Notably, after 7,d, the highest concentration was measured in the lymph nodes, and the largest amount was found in the liver. A comparison with the results of two previous ADME investigations of , -peptides (cf. Table,1) reveals that the distribution of the compounds within the animals is structure-dependent, and that there is a full range from oral availability with rather rapid excretion (of a tetrapeptide) to essentially complete lack of both oral absorption and excretion after i.v. administration (of a highly charged octapeptide). A discussion is presented about the in vivo stability and ,drug-ability' of peptides. In general, , -peptides bearing proteinogenic side chains are compared with peptides consisting entirely of D - , -amino acid residues (the enantiomers of the ,natural' building blocks), and suggestions are made regarding a possible focus of future biomedical investigations with , -peptides. [source]