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Absolute bioavailability of himantane in rabbits.
E A Litvin1, D V Bastrygin, G B Kolyvanov
1V. V. Zakusov Institute of Pharmacology, Russian Academy of Medical Sciences, Moscow, Russia. zlanomar@gmail.com
Bulletin of Experimental Biology and Medicine
|July 21, 2012
Summary
Himantane exhibits low oral bioavailability (7.95%) in rabbits, indicating significant first-pass metabolism in the liver. The drug is extensively metabolized into compounds with m/z 266 and 250.
Area of Science:
- Pharmacology
- Drug Metabolism
- Pharmacokinetics
Background:
- Understanding drug absorption, distribution, metabolism, and excretion (ADME) is crucial for effective therapeutic use.
- Himantane's pharmacokinetic profile requires detailed investigation to optimize its clinical application.
Purpose of the Study:
- To compare the pharmacokinetic parameters of himantane and its metabolites in rabbit blood plasma.
- To determine the absolute bioavailability of himantane following intravenous and oral administration.
- To elucidate the metabolic pathways and identify major metabolites of himantane.
Main Methods:
- Single dose administration of himantane (25 mg IV, 100 mg PO) to rabbits.
- Blood plasma sampling at various time points post-administration.
- Analysis of himantane and its metabolites using mass spectrometry.
Main Results:
- Himantane demonstrated low absolute oral bioavailability, calculated at 7.95%.
- Evidence of a significant first-pass effect was observed.
- Extensive hepatic metabolism of himantane was confirmed, yielding metabolites with m/z 266 and 250.
Conclusions:
- Himantane undergoes substantial first-pass metabolism, leading to limited systemic exposure after oral administration.
- The identified metabolites (m/z 266 and 250) are key products of himantane's hepatic biotransformation.
- Further research is warranted to explore strategies for improving himantane's oral bioavailability.
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