Cardiovascular and neuromuscular effects of dimethyl tubocurarine in anaesthetized cats and rhesus monkeys.

Intravenous dose-response relationships for dimethyl tubocurarine showed that vagal blockade only became appreciable (50-83%) at doses 8-16 times those sufficient for full neuromuscular paralysis in anaesthetized cats (0.0625 mg/kg) and rhesus monkeys (0.125 mg/kg); heart rate was unchanged. Sympathetic function was unimpaired by supramaximal paralysing doses of 0.5 and 1 mg/kg in cats, but was reduced (20-41%) by comparable neuromuscular paralysing doses of 1 and 2 mg/kg in rhesus monkeys; these doses decreased carotid arterial pressure by 22-36%. The duration of action of dimethyl tubocurarine was prolonged; more than 60 min was required for recovery from full neuromuscular paralysis; the drug was even more persistent in rhesus monkeys than in cats. Thus the need remains for a drug resembling dimethyl tubocurarine in its highly specific action at the neuromuscular junction, but with a much shorter duration of action.