Increased brain uptake of morphine in the presence of the antihistamine tripelennamine

Abstract

Abstract Disposition of [6 3H (N)]morphine in plasma, brain and liver of rats was studied 15 min after intravenous injection of either a 2 mg kg−1 dose of morphine or a combination of the same dose of morphine with a 6 mg kg−1 dose of tripelennamine. The concentrations of morphine in brain and the brain to plasma morphine ratios in animals receiving the combination of drugs concurrently were significantly higher than those in the control morphine group. No significant differences were seen in the morphine or morphine metabolite concentrations in plasma and liver or liver to plasma morphine concentration ratios in the 2 groups. Data suggest that pharmacokinetic factors play a role in the potentiation of opiate effects by antihistamine on concurrent i.v. administration of the two drugs.