Modification of the antihypertensive effect of indapamide by indomethacin.

Oral treatment with indapamide was found to reduce blood pressure of hypertensive rats but not of normotensive rats. Chronic indomethacin treatment had no effect on blood pressure of untreated normotensive and hypertensive rats. Also indomethacin did not modify the antihypertensive effect of indapamide excluding the direct involvement of PGs in the antihypertensive effect of indapamide. Vascular reactivity to pressor agents NA, ADR and ANG was significantly increased after indomethacin treatment. This may be due to the blockade of the actions of PG in modifying vascular reactivity to vasoconstrictor agents or may be a direct effect of indomethacin on calcium fluxes. Indapamide reduced the reactivity to NA and ANG in the presence of indomethacin suggesting that the antihypertensive effect of indapamide may be through a decrease in reactivity to pressor agents which is independent of increase in the synthesis of vasodilator PGs.