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The central and peripheral haemodynamic effects of the administration of 10 mg nifedipine sublingually in 6 patients with essential hypertension were compared with those observed after the administration of one 20 mg slow release tablet of nifedipine in 7 other hypertensive patients of the same age. The circulatory effects in the forearm were studied by pulsed Doppler velocimetry which allowed simultaneous measurement of the diameter of the brachial artery and of the velocity of blood flow. Both forms of administration significantly reduced the blood pressure by a significant reduction in total peripheral resistance. This reduction in total peripheral resistance was more significant (p less than 0.001 vs p less than 0.01) and more rapid with sublingual administration and was associated with a greater increase in heart rate and cardiac output. Both forms of administration induced an increase in brachial arterial blood flow due to a simultaneous increase in vessel calibre and velocity of blood flow. The results of this study show that both forms of administration act directly on the vessel wall of the arterioles and great arteries leading to a fall in blood pressure associated with an increase in peripheral blood flow. Sublingual nifedipine would seem to be the drug of choice for the treatment of hypertensive crises, whilst the slow release preparation with its lesser baroreflex stimulation would appear better suited for the long-germ treatment of essential hypertension.

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 less than 0.001). Propranolol reduced heart rate (p less than 0.001), while MK 421 did not change it. Brachial artery diameter, blood velocity and flow increased after MK 421 (p less than 0.001), but were not changed after propranolol therapy. Forearm vascular resistance decreased after MK 421 (p less than 0.001) and after propranolol (p less than 0.05). Forearm venous tone was unaffected on MK 421, but increased after propranolol (p less than 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.