Drugs online research references
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Acyclovir controlled-release capsules (CRCs) were prepared by a three-step process: (1) melt granulation of acclovir; (2) coating of granules with ethyl-cellulose, (3) incorporation of coated granules into hard gelatin capsules. In vitro release experiments showed that the main factors affecting the release rate were the mean particle size of the actylovir raw material and the amount of coating material applied. Release of acyclovir from the capsules was in accordance with the Higuchi equation. Pharmacokinetic studies in dogs after oral administration of acyclovir controlled-release capsules showed that the formulation was successful in providing slow release of aciclovir and was superior to a commercially available controlled-release formulation.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11694016&dopt=Abstract
J Pharm Biomed Anal. 1998 Oct;18(1-2):249-54.
Determination and pharmacokinetics of acyclovir after ingestion of suspension form.
Jankowski A, Jankowska AL, Lamparczyk H.
Medical Center of Postgraduate Education, Department of Biopharmaceutics, Bydgoszcz, Poland.
The study describes, simple, precise, sensitive and accurate HPLC assay with spectrofluorimetric detection for the determination of acyclovir in human plasma. The method was linear over a range 25 1200 ng ml(-1). The average yield in this method exceeded 80%. Limits of quantitation and detection were 25 and 10 ng ml(-1), respectively. On the basis of reported method, a single-dose of pharmacokinetics on 24 men, in two doses (200 and 400 mg) of acyclovir suspension has been investigated. Pharmacokinetic parameters obtained from both doses of the drug were compared. The linearity of acyclovir pharmacokinetics in the investigated dose ranges has been confirmed.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9863965&dopt=Abstract
Drug Metab Dispos. 1994 Jan-Feb;22(1):55-9.
Metabolic fate and pharmacokinetics of the acyclovir prodrug valaciclovir in cynomolgus monkeys.
de Miranda P, Burnette TC.
Division of Experimental Therapy, Burroughs Wellcome Co., Research Triangle Park, NC 27709.
Valaciclovir, the L-valyl ester of acyclovir (ZOVIRAX), demonstrated good oral absorption and nearly complete conversion to acyclovir in cynomolgus monkeys, indicating its suitability as an orally administered prodrug. The major urinary metabolites of [8-14C]valaciclovir, administered orally (10 and 25 mg/kg) or intravenously (10 mg/kg) to male monkeys, were acyclovir (46%-59% of urinary radioactivity), 8-hydroxyacyclovir (25%-30%), and 9-(carboxymethoxymethyl)guanine (CMMG) (11%-12%). Following oral and intravenous dosing, intact prodrug accounted for only 0.5% and 6% of urinary radioactivity, respectively. Dose-independent kinetics were observed for acyclovir derived from orally administered [8-14C]valaciclovir at the 10 and 25 mg/kg dose levels, with both AUC (24 and 60 microM.hr, respectively) and Cmax (8 and 23 microM, respectively) increasing nearly in proportion to the dose. Acyclovir was present in plasma at all sampling times (5 min to 7 hr postdose) after both oral doses, whereas the prodrug was not detected following either oral dose. The elimination of acyclovir after oral administration was monophasic, with an apparent half-life of 1.3-1.5 hr. Similar to acyclovir, both 8-hydroxyacyclovir and CMMG demonstrated dose-independent kinetics with apparent elimination half-lives of 1-1.6 hr. Intravenously administered [8-14C]valaciclovir (10 mg/kg) was rapidly converted to acyclovir, with the elimination half-life of acyclovir (0.9 hr) being 1.5-fold that of the prodrug (0.6 hr). The oral bioavailability of acyclovir derived from valaciclovir in cynomolgus monkey was 67 +/- 13%, representing a significant improvement over the limited bioavailability after acyclovir administration to primates.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=8149890&dopt=Abstract
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