A comparison of the pharmacokinetic properties of these agents is listed in Table 19.2. All three drugs are well absorbed following oral administration. Verapamil and diltiazem undergo greater first-pass metabolism rel-ative to nifedipine, resulting in lower bioavailability of the former two drugs. Hepatic metabolism of nifedipine is complete, yielding inactive metabolites; this is unlike verapamil and diltiazem, whose metabolites have phar-macological activity. Verapamil is metabolized stereose-lectively in favor of the more active ( ) enantiomer, thus requiring higher plasma concentrations after oral administration.