Potentiation of the epileptogenic effect of penicillin G by marihuana smoking.

Abstract

Marihuana smoking is known to produce many subtle neurological modifications in animal and man. We investigated the effects of subconvulsive doses of penicillin after acute or chronic marihuana smoking. Twenty-four mongrel dogs weighing from 15 to 25 kg received 4 mg morphine per kilogram, intramuscularly, and 750 000 IU sodium penicillin G per kilogram, intravenously. In acute experiments, the animals smoked eight cigarettes containing approximately 6 mg of Δ9-tetrahydrocannabinol. In chronic experiments, they smoked four cigarettes per day for 10 weeks before being studied. Ten animals (five controls and five acute smokers) were observed visually while the electrocorticogram (ECoG) was recorded in the 14 others (five controls, five acute, four chronic). This last group received 20–30 mg succinylcholine chloride as muscle relaxant. Penicillin had no effect either on the behaviour or on the ECoG in 9 of the 10 controls. On the other hand, 9 out of the 10 acute smokers showed modifications (coarse tremors of the limbs and epileptiform waves). Two of the four chronic smokers had typical epileptiform episodes. The results suggest that marihuana smoking produces a blood–brain barrier permeability change towards sodium penicillin G. Another explanation could be that Cannabis modifies the excitability threshold of the brain.