The likelihood of remaining normotensive following antihypertensive drug withdrawal

To determine the proportion and characteristics of mild hypertensives who remain normotensive after withdrawal from drug treatment.

Longitudinal descriptive study.

A university family practice unit (FPU) and a large steel company (DOFASCO) in Hamilton, Ontario.

Participants were 107 of 125 (86%) eligible hypertensives at the two sites; 103 (96%) subjects completed the study.

Subjects discontinued antihypertensive medication and were followed until blood pressure (BP) became elevated or for 12 months, whichever was shorter.

BPs were monitored according to a predefined schedule and before, during, and after mental and physical stress tests. Thirty-eight (37%, 95% confidence interval [CI] 27-46%) subjects remained normotensive at 12 months. Predictors of remaining normotensive included lower medicated standing diastolic blood pressure (DBP) (87.6 versus 91.8 mm Hg, 95% CI for the difference 2.2-6.2, p less than 0.001) and longer duration of normotension on drugs (12.6 months versus 8.7, 95% CI for the difference 0.9-6.9, p = 0.012). There was no significant relationship between maintenance of normotension and age, medication potency, duration of hypertension, weight, lying BP, change in heart rate, or BP during mental or physical stress tests; the power to detect a clinically important difference in lying DBP was 99% but for other variables was lower (21-75%).

The probability of hypertensives' remaining normotensive for one year after drug withdrawal increases as the medicated standing DBP decreases and as the number of months of BP control while on medication increases. Studies with larger sample sizes are warranted to determine whether other variables may be significant predictors.