Drug Interaction Report

Angiotensin-converting enzyme (ACE) inhibitors may interfere with the effects of both endogenous and exogenous erythropoietin, although data are conflicting with respect to the latter. A retrospective investigation of 43 dialysis patients treated with human recombinant erythropoietin for an average of ten months found that the group also receiving captopril had lower hemoglobin and hematocrit levels than the control group when given the same dosage of erythropoietin, and the difference was statistically significant. However, another retrospective investigation found no significant differences in the mean hematocrit level and erythropoietin dosage in 14 stable hemodialysis patients for up to 16 weeks before and 16 weeks after initiation of ACE inhibitor therapy. Previous studies have suggested that ACE inhibitors may interfere with hematopoiesis by decreasing the synthesis of endogenous erythropoietin or decreasing bone marrow production of red blood cells, but an actual pharmacokinetic or pharmacodynamic interaction with erythropoietin has not been reported. Until further data are available, it may be appropriate to monitor patients for potentially diminished hematopoietic response to recombinant erythropoietin therapy following the addition of an ACE inhibitor. It is not known if other erythropoiesis-stimulating agents are similarly affected.

GENERALLY AVOID: Moderate-to-high dietary intake of potassium can cause hyperkalemia in some patients who are using angiotensin converting enzyme (ACE) inhibitors. In some cases, affected patients were using a potassium-rich salt substitute. ACE inhibitors can promote hyperkalemia through inhibition of the renin-aldosterone-angiotensin (RAA) system.

MANAGEMENT: It is recommended that patients who are taking ACE inhibitors be advised to avoid moderately high or high potassium dietary intake. Particular attention should be paid to the potassium content of salt substitutes.