Effects of seven drugs of abuse on action potential repolarisation in sheep cardiac Purkinje fibres

Seven drugs of abuse have been examined for effects on the action potential in sheep isolated cardiac Purkinje fibres. Phencyclidine (5 μM) induced a significant increase (30.7%) in action potential duration at 90% repolarisation (APD 90). Similarly, 10 μM 3,4-methylenedioxymethamphetamine (MDMA, ‘Ecstasy’) induced a significant increase in APD 90 of 12.1%. Although Δ 9-tetrahydrocannabinol (0.1 μM) induced a small, but statistically significant, 4.8% increase in APD 90, no effects were observed at 0.01 or 1 μM. Cocaethylene (10 μM) induced a significant shortening of APD 90 (− 23.8%). Cocaine (up to 1 μM), (+)-methamphetamine (‘Speed’; up to 5 μM), and the heroin metabolite, morphine (up to 5 μM), had no statistically significant effects. The possible significance of these findings is discussed in the context of other recognised cardiac effects of the tested drugs.