A comparison of alphaprodine and meperidine pharmacokinetics.

We have developed a gas-liquid chromatographic analysis for measuring plasma alphaprodine. The analysis is sufficiently sensitive for studying therapeutic-dose pharmacokinetics in man. Single intravenous bolus injections of either alphaprodine or meperidine were given to volunteer subjects. Plasma concentration data were fitted to a biexpoential equation and pharmacokinetic parameters were calculated. Consistent with alphaprodine's shorter clinical duration compared to meperidine, we found that plasma levels of alphaprodine decline at a more rapid rate. Plasma clearances for the two narcotics are nearly identical (1.04 l./kg/min for alphaprodine and 1.01 l./kg/min for meperidine). The apparent volume of distribution for alphaprodine is smaller than for meperidine (1.90 l./kg for alphaprodine and 3.37 l./kg for meperidine).