A trial of oral delta-1-(trans)-tetrahydrocannabinol in reversible airways obstruction.

Sixteen patients with proven reversible airways obstruction were admitted to a double-blind study to compare the bronchodilator effects of oral delta-1-(trans)-tetrahydrocannabinol (delta-1-THC) and salbutamol. Measurements of forced vital capacity, forced expired volume in one second, peak expiratory flow rate, and maximum expiratory flow rate at 50 percent vital capacity after 10 mg oral delta-1-THC did not differ significantly from the effect of placebo, whereas increases after salbutamol were significant. Analyses of mood, pulse rate, blood pressure, and electrocardiogram showed no important changes after oral delta-1-THC. In vitro studies with isolated tracheal muscle indicate that the activity of delta-1-THC is 1,000 times less than the equivalent dose of isoprenaline, and the effect of delta-1-THC is not abolished by beta-adrenoreceptor blocking agents. It is concluded that oral delta-1-THC, at a dose of 10 mg, does not produce clinically significant bronchodilatation in patients with reversible airways obstruction.