Captopril

Summary of Interactions with Vitamins, Herbs, and Foods
(for details about the summarized interactions, read the full article)

May be Beneficial: Depletion or interference—The medication may deplete or interfere with the absorption or function of the nutrient. Taking these nutrients may help replenish them.	Zinc
May be Beneficial: Side effect reduction/prevention—Taking these supplements may help reduce the likelihood and/or severity of a potential side effect caused by the medication.	Iron
Avoid: Adverse interaction—Avoid these supplements when taking this medication because taking them together may cause undesirable or dangerous results.	High-potassium foods* Potassium supplements* Salt substitutes*
Supportive interaction	None known
Reduced drug absorption/bioavailability	None known

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.

Iron
In a double-blind study of patients who had developed a cough attributed to an ACE inhibitor, supplementation with iron (in the form of 256 mg of ferrous sulfate per day) for four weeks reduced the severity of the cough by a statistically significant 45%, compared with a nonsignificant 8% improvement in the placebo group.¹¹

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.

11. Lee SC, Park SW, Kim DK, et al. Iron supplementation inhibits cough associated with ACE inhibitors. Hypertension 2001;38:166–70.

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The information presented in Healthnotes is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over-the-counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires March 2005.