Three male beagle dogs were given 2.5 mg/kg doses of [14C]triprolidine HCl monohydrate (2.09 mg/kg of the free base) by intravenous and oral routes, in a nonrandomized cross-over experiment. After either route of administration, approximately 75% of the dose was excreted in the urine, and the remainder was excreted in the feces. Triprolidine was extensively metabolized, with less than 1% of the parent drug recovered in the excreta after either route of administration. Three metabolites were isolated from excreta and identified, including the major metabolite (metabolite 1, 219C69), in which the toluene ring methyl group was oxidized to a carboxylic acid, a metabolite (metabolite 2) in which the pyrrolidine ring was opened with oxidation of the terminal carbon to a carboxylic acid (a gamma-aminobutyric acid), and a metabolite (metabolite 3) that was a pyrrolidinone derivative of 219C69. Other metabolites in urine and feces were present in amounts too small for quantitation or identification. Route of administration had little effect on the metabolic pattern of triprolidine. Thus, after oral administration of triprolidine, a mean of 49.1% of the dose was excreted as 219C69, 12.0% as metabolite 2, 3.4% as metabolite 3, and 0.6% as triprolidine, while after intravenous administration, a mean of 50.8% of the dose was excreted as 219C69, 11.1% as metabolite 2, 4.2% as metabolite 3, and 0.8% as triprolidine. Plasma contained triprolidine, 219C69, and metabolite 2, as well as other apparent metabolites that were present at levels too low for quantitation. Mean pharmacokinetic parameters calculated for triprolidine after intravenous dosing were: CL = 24.4 ml/min/kg, Vdss = 5.8 liters/kg, and Vc = 1.6 liters/kg.(ABSTRACT TRUNCATED AT 250 WORDS)