Intra-arterial ambulatory blood pressure monitoring in the assessment of antihypertensive drugs

Direct measurement of blood pressure in ambulatory patients was performed with the intra-arterial “Oxford System” to assess the effectiveness of differing antihypertensive agents. The betablocker, metoprolol (200 mg daily), decreased daytimed blood pressure from 174/95 mmHg to 158/85 mmHg; the combination of metoprolol and chlorthalidone (25 mg daily) further decreased the mean daytime pressure to 143/78 mmHg (p < 0.001 systolic, p < 0.005 diastolic). The calcium channel blockers, nifedipine (20–40 mg twice daily) and verapamil (120–160 mg three times daily), each significantly decreased the nifedipine, but decreased significantly with verapamil. The angiotensin converting enzyme inhibitor, enalopril (20–40 mg daily), significantly decreased blood pressure for 18 of 24 hours, the antihypertensive effect being most pronounced during the daytime period. These experiences indicate that the technique of direct ambulatory blood pressure monitoring is of value in studying both the efficacy and the duration of antihypertensive treatment.mean hourly blood pressure during most of the day (23 of 24 hours with nifedipine, 15 of 24 hours of verapamil). Heart rate did not change with nifedipine, but decreased significantly with verapamil. The angiotensin converting enzyme inhibitor, enalopril (20–40 mg daily), significantly decreased blood pressure for 18 of 24 hours, the antihypertensive effect being most pronounced during the daytime period. These experiences indicate that the technique of direct ambulatory blood pressure monitoring is of value in studying both the efficacy and the duration of antihypertensive treatment.