Twelve treated hypertensive patients (ages 58-71 years) who had also been treated for joint disease participated in a randomized double-blind crossover placebo-controlled study to investigate the effects of indomethacin (25 mg three times daily) on blood pressure and biochemical parameters over a 6-week period. 2. Blood pressure was increased in all patients throughout the indomethacin treatment period (P less than 0.001)--average mean blood pressure increases were 9 mmHg (casual), 8 mmHg (supine), 10 mmHg (standing). 3. The blood pressure increase during indomethacin treatment was independent of the particular antihypertensive regimen in use. 4. Plasma aldosterone concentration was reduced by 50% (P less than 0.01), plasma renin activity was reduced by 43% (P = 0.102) and plasma urea concentration was increased by 17% (P less than 0.001) during indomethacin treatment. 5. The findings confirm that indomethacin impairs the blood pressure lowering effect of antihypertensive regimens.
