Comparison of oral MK 421 and propranolol in mild to moderate essential hypertension and their effects on arterial and venous vessels of the forearm

The efficacy of MK 421 and propranolol was compared in 48 patients with mild to moderate hypertension. Each patient was randomly assigned to receive 1 of the drugs for 12 weeks. Additionally, a subgroup of 28 patients underwent studies of forearm arterial and venous circulation by means of pulsed Doppler and mercury-in-silastic plethysmography. Both drugs reduced supine and standing blood pressure (BP) (p < 0.001). Propranolol reduced heart rate (p < 0.001), while MK 421 did not change it. Brachial artery diameter, blood velocity and flow increased after MK 421 (p < 0.001), but were not changed after propranolol therapy. Forearm vascular resistance decreased after MK 421 (p < 0.001) and after propranolol (p < 0.05). Forearm venous tone was unaffected on MK 421, but increased after propranolol (p < 0.01). Thus, in moderate hypertension, 3 months of treatment with MK 421 or propranolol similarly decrease BP, but affect the forearm circulation differently: MK 421 dilates both the brachial artery and the arterioles of the forearm, but does not affect the venous vessels and propranolol causes little arterial change but increases the forearm venous tone.