1. Minoxidil, an experimental arteriolar dilator, has been used in conjunction with a diuretic and a sympathetic nervous system suppressant in 510 patients with refractory hypertension, of whom 323 remain on treatment. The results in two of a total of twenty aetiological groups are described.
2. Of eighty-eight patients with refractory hypertension who were on maintenance haemodialysis when minoxidil was first administered, forty-six currently remain on treatment. In these the average blood pressure fell to 150/100 mmHg from an average of 190/130 mmHg before minoxidil. Healing occurred in the nineteen who had had grade 3 or 4 optic fundi. Side effects resulted in discontinuation of the drug in four of the eighty-eight patients.
3. Thirty-five patients with essential hypertension and good renal function were treated for from 3 to 12 months. The supine blood pressures before minoxidil averaged 280/128 mmHg and averaged 160/97 mmHg whilst the drug was given. The serum creatinine concentration did not change significantly. The optic fundi improved in nine; in nine others episodes of congestive heart failure were reduced in frequency.
4. If careful attention is directed to salt balance and to heart rate, minoxidil may help control otherwise refractory hypertension.