Summary
Following i. v. administration, the plasma concentration-time curve of verapamil could best be described by either a mono- or biexponential equation. Total plasma clearance (1.26 l/min) approached liver blood flow (1.5 l/min), so it can be concluded that its clearance is liver blood flow-dependent. Although absorption was almost complete after oral administration, absolute bioavailability (20%) was low, due to extensive hepatic first-pass metabolism. The approach using stable isotope-labelled and unlabelled drug permits simultaneous administration by the intravascular and extravascular routes, thus allowing determination of absolute bioavailability in a single experiment.
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Eichelbaum, M., Somogyi, A., von Unruh, G.E. et al. Simultaneous determination of the intravenous and oral pharmacokinetic parameters of D,L-verapamil using stable isotope-labelled verapamil. Eur J Clin Pharmacol 19, 133–137 (1981). https://doi.org/10.1007/BF00568400
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DOI: https://doi.org/10.1007/BF00568400