Khat chewing and arterial blood pressure. A randomized controlled clinical trial of alpha-1 and selective beta-1 adrenoceptor blockade.

Objective: The aim of this work was to study prospectively the effect of alpha-1 and selective beta-1 adrenoceptor blockade on cardiovascular effects of khat chewing in healthy volunteers.

Methods: Sixty-three male volunteers chewed khat for 3 hours on 3 separate occasions, 1 or 2 weeks apart. Fifty age and weight matched male controls did not chew. The khat chewers received in a double blind 3-arm crossover design either indoramin 25 mg, atenolol 50 mg or placebo one hour before starting to chew. The non-chewing controls received atenolol 50 mg on a separate occasion. Pulse and blood pressure were measured at regular intervals before, during and after the chewing period. The study was carried out in Sana'a, Yemen between December 2001 and November 2003.

Results: Khat chewers in the atenolol treated group had significantly lower readings for systolic blood pressure (SBP) and pulse rate one, 2 and 3 hours after starting to chew than khat chewers pre-treated with placebo or indoramin and comparable to non-khat chewers. Three hour SPB readings in khat chewers with placebo, with atenolol and with indoramin (mean values [95% confidence interval]) were 123 (120.2-125.7), 115.7 (113.0-118.4), and 119.8 (116.9-122.8) (p<0.0001). Blood pressure and pulse rate were not altered in non-khat chewers taking 50 mg atenolol. Diastolic blood pressure during khat chewing rose in the atenolol, indoramin and placebo groups.

Conclusion: The effect of khat chewing on systolic blood pressure and pulse rate is blocked by atenolol but not by indoramin. Beta-1 adrenoreceptors are probably important in mediating the cardiovascular effects of khat in man.