Studies on the absorption and disposition of meptazinol following rectal administration

1 Rectal administration of the new analgesic drug, meptazinol, resulted in rapid absorption of the compound both in the monkey and in man. Peak plasma levels were observed within 0.5 h of dosing. 2 Absorption of the drug following rectal administration was extensive as shown by the recovery of 65-90% of the dose in the urine. 3 Despite substantial inter-individual variation in the observed maximum plasma concentrations of the drug, it was still evident that concentrations after rectal dosage were considerably higher than when the same dosage was given orally. 4 Elimination of the drug from plasma took place rapidly in an apparently mono-exponential manner in both species. The half-life of elimination in monkeys was 1.25 h and in man 2.0 h.