Interactions between non-steroidal anti-inflammatory drugs and antihypertensives and diuretics.

Non-steroidal anti-inflammatory drugs (NSAIDs) may increase blood pressure and antagonise the effects of antihypertensive agents. They can cause salt and water retention and an increase in extracellular volume. NSAIDs also cause a decrease in prostaglandin synthesis in blood vessel walls which removes a direct vasodilatory influence and also increases the vascular response to vasoconstrictor stimuli. The hypotensive effects of frusemide and captopril are due in part to their stimulation of prostaglandin synthesis. Hence the antagonism of the hypotensive effect of these agents is probably due to NSAID-induced inhibition of prostaglandin synthesis. However, the interactions of NSAIDs with the other antihypertensive agents may not be related to inhibition of antihypertensive-induced release of prostaglandin but to independent and opposing actions of the NSAIDs on the various physiological mechanisms which regulate blood pressure. Clinicians should remain alert to these potential drug interactions.