Indomethacin does not attenuate the effects of hydralazine in normal subjects.

Indomethacin 100 mg/day or matching placebo was given for 2.5 days to 9 healthy volunteers in a double-blind cross-over study, followed by an intravenous injection of 0.2 mg/kg of hydralazine. Compared to placebo, indomethacin produced no statistically significant change in pulse rate or blood pressure in both standing and supine positions. Hydralazine injection was followed by a statistically significant fall in lying and standing diastolic pressure and a rise in lying and standing pulse after both indomethacin and placebo pretreatments. There were no significant differences in these effects following indomethacin compared to placebo pretreatment. These results do not support the hypothesis that endogenous prostaglandins are involved in the mechanism of action of hydralazine.