The treatment of resistant hypertension.

Resistant hypertension can be defined in terms of lack of blood pressure response to hypotensive agents, but there may be a big difference between standing and lying blood pressure levels. In general target organ damage and papilloedema improve if the standing blood pressure is controlled; however, progression can occasionally be documented when only the supine blood pressure remains uncontrolled. Resistant hypertension was a frequent phenomenon when ganglion blocking agents and hydrallazine were the only effective hypotensive agents. With the advent of the thiazides, effective control of the blood pressure became the exception rather than the rule; however, it was not until the advent of adrenergic blocking agents that reduction of supine blood pressures was regularly achieved. The addition of hydrallazine or prazosin to a combination of a thiazide and beta-adrenoreceptor blocking agent produces a further significant fall in the blood pressure lying and standing. This combination will control the blood pressure in most patients, but a few remain refractory to maximum doses and will require treatment with oral diazoxide or minoxidil. Both these powerful vasodilators are very effective in resistant hypertension. Oral diazoxide permits excellent control and allows a 10-fold reduction in the doses of other agents. Minoxidil usually needs to be combined with moderate doses of beta-blocking agents to reduce the marked reflex tachycardia. Only a 50% reduction in other hypotensive agents was achieved in patients treated with minoxidil and two patients proved resistant to minoxidil, but subsequently responded to oral diazoxide.