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Captopril

Also indexed as: Capoten®

Combination drugs: Acezide®, Capto-Co®, Captozide®, Co-Zidocapt

Captopril is an angiotensin-converting enzyme (ACE) inhibitor—a family of drugs used to treat high blood pressure and some types of heart failure. Captopril is also used to slow the progression of kidney disease in people with diabetes.

Interactions with Dietary Supplements

Potassium
An uncommon yet potentially serious side effect of taking ACE inhibitors is increased blood potassium levels.1 2 3 This problem is more likely to occur in people with advanced kidney disease. Taking potassium supplements,4 potassium-containing salt substitutes (No Salt®, Morton Salt Substitute®, and others),5 6 7 or large amounts of high-potassium foods at the same time as ACE inhibitors could cause life-threatening problems.8 Therefore, individuals should consult their healthcare practitioner before supplementing additional potassium and should have their blood levels of potassium checked periodically while taking ACE inhibitors.

Zinc
Preliminary research has found significant loss of zinc in urine triggered by taking captopril.9 In this trial, depletion of zinc reduced red blood cell levels of zinc. Although details remain unclear, it now appears that chronic use of captopril may lead to a zinc deficiency.10

It makes sense for people taking captopril long term to consider taking a zinc supplement or a multimineral tablet containing zinc as a precaution. (Such multiminerals usually contain no more than 99 mg of potassium, probably not enough to trigger the above-mentioned interaction.) Supplements containing zinc should also contain copper, to protect against a zinc-induced copper deficiency.

Summary of Interactions for Captopril

Depletion or interference Zinc
Adverse interaction High-potassium foods*
Potassium supplements*
Salt substitutes*
Side effect reduction/prevention None known
Supportive interaction None known
Reduced drug absorption/bioavailability None known

For the convenience of the reader, the information in the summary is categorized as follows: “Depletion or interference” indicates the drug may deplete or interfere with the absorption or function of the supplement or herb. “Adverse interaction” indicates that the supplement or herb used together with the drug may result in undesirable effects. “Side effect reduction/prevention” indicates the supplement or herb may reduce the likelihood and/or severity of a potential side effect caused by the drug. “Supportive interaction” indicates the supplement or herb may support or aid the function of the drug. “Reduced drug absorption/bioavailability” indicates that the supplement or herb may decrease the absorption and/or activity of the drug in the body. An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.

References:

1. Good CB, McDermott L, McCloskey B. Diet and serum potassium in patients on ACE inhibitors. JAMA 1995;274:538.

2. Rush JE, Merrill DD. The Safety and tolerability of lisinopril in clinical trials. J Cardiovasc Pharmacol 1987;9(Suppl 3):S99–107.

3. Sifton DW, ed. Physicians’ Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 1965–8.

4. Burnakis TG, Mioduch HJ. Combined therapy with captopril and potassium supplementation. A potential for hyperkalemia. Arch Intern Med 1984;144:2371–2.

5. Burnakis TG. Captopril and increased serum potassium levels. JAMA 1984;252:1682–3 [letter].

6. Ray K, Dorman S, Watson R. Severe hyperkalemia due to the concomitant use of salt substitutes and ACE inhibitors in hypertension: a potentially life threatening interaction. J Hum Hypertens 1999;13:717–20.

7. Sifton DW, ed. Physicians’ Desk Reference. Montvale, NJ: Medical Economics Company, Inc., 2000, 1965–8.

8. Stoltz ML. Severe hyperkalemia during very-low-calorie diets and angiotensin converting enzyme use. JAMA 1990;264:2737–8 [letter].

9. Golik A, Modai D, Averbukh Z, et al. Zinc metabolism in patients treated with captopril versus enalapril. Metabolism 1990;39:665–7.

10. Golik A, Zaidenstein R, Dishi V, et al. Effects of captopril and enalapril on zinc metabolism in hypertensive patients. J Am Coll Nutr 1998;17:75–80.