Interaction of ACE inhibitors and aspirin in patients with congestive heart failure

The beneficial effects of aspirin and ACE inhibitors in CHF have been well established; however, the clinical relevance of the drug interaction between these agents remains controversial. The exact mechanism of this interaction is not known, but the proposed theory involves the opposing effects of aspirin and ACE inhibitors on prostaglandins. The medical literature dose not provide a clear picture of the clinical significance of concomitant aspirin and ACE inhibitor therapy. Some studies suggest that the dose of aspirin may influence the clinical relevance of this interaction. Short-term use of aspirin ≥300 mg was found to attenuate enalapril's effect on hemodynamic variables. However, short-term use of low-dose aspirin (236 mg) produced no effect on blood pressure. Patients with CHF who require therapy with both aspirin and ACE inhibitors may want to consider low doses of aspirin with active monitoring of hemodynamic parameters. However, chronic aspirin therapy in patients with CHF on concomitant ACE inhibitors has not been adequately studied at this time. Data concerning a possible interaction between angiotensin II receptor antagonists and aspirin are not available. However, because angiotensin II receptor antagonists do not interfere with kininase II activity, it would seem unlikely that aspirin would interact similarly with an angiotensin II receptor antagonist. Further studies are needed to examine the exact mechanism of the interaction between aspirin and ACE inhibitors. These studies should focus on the effects of different doses of aspirin given concomitantly with ACE inhibitors in patients with CHF. Prospective, randomized studies are also needed to determine the long-term effects of aspirin and ACE inhibitor therapy on mortality in patients with CHF.