Interactions of clonidine and nifedipine in moderately severe hypertensive patients

In ten patients (age: 47-59 yr) with moderately severe essential hypertension, the humoral and hemodynamic effects of a 4-day therapy with 2 x 75 micrograms clonidine, 2 x 20 mg nifedipine (slow-release), and their combination were investigated and compared with baseline values. The following measurements were observed under clonidine (C), nifedipine (N), and on combination (C/N), respectively: heart rate fell significantly under C from a mean of 79 to 67/min (P less than .05), increased to 73/min after N (P greater than .05) and fell again to 68/min under combination (P less than .05). Systolic blood pressure (Riva-Rocci method) decreased from a mean of 184 to 171 (C), 168 (N) and 161 mm Hg (C/N), respectively (P less than .01). Diastolic blood pressure was also significantly altered (113 vs. 104 (C), 107 (N), and 100 mm Hg (C/N); P less than .05). Stroke volume (ECHO) was not altered significantly (77 vs. 71 (C), 79 (N), and 80 mL (C/N), respectively), whereas cardiac output dropped from 5.9 to 4.9 L/min (C; P less than .05), increased to 5.7 (N; P greater than .05), and dropped again to 5.3 L/min (C/N; P greater than .05). Peripheral vascular resistance increased from a mean of 2091 to 2297 (C), fell to 1933 (N), and increased again to 2138 dyn/sec/cm-5 (C/N). Plasma norepinephrine levels fell from 440 to 281 (C; P less than .01), increased to 391 (N; P greater than .05), and fell again to 404 pg/mL (C/N; P greater than .05).(ABSTRACT TRUNCATED AT 250 WORDS)