Sustained calcium channel blockade in the treatment of severe hypertension. A two year experience. Thirty-nine patients with severe hypertension (diastolic blood pressure greater than 120 mm Hg) predominantly drawn from an inner-city population were placed on nifedipine gastrointestinal therapeutic system (GITS) for long-term treatment to achieve a sustained diastolic blood pressure less than 95 mm Hg. Fourteen patients failed to complete 6 months of therapy. For the 25 who remained in treatment for 6 months or more, systolic/diastolic blood pressure reductions were 62 +/- 5/40 +/- 2 mm Hg at 6 months; for those followed more than 12 months (n = 18), 58 +/- 7/37 +/- 3 mm Hg at 12 months; and for those followed more than 18 months (n = 11), 54 +/- 6/37 +/- 3 mm Hg at 18 months. Overall, 75% of these severely hypertensive patients were controlled with nifedipine GITS alone; 80% required 90 mg/day or more. During the two years of observation, no patient had a severe medical event, and 44% of those who entered remain in treatment. Left ventricular hypertrophy, as determined by echocardiography, diminished significantly during the course of treatment. These results indicate nifedipine GITS is well-tolerated and effective as monotherapy in the treatment of severe hypertension. 