Quinapril is an angiotensin-converting enzyme (ACE) inhibitor, a family of drugs used to treat high blood pressure and some types of heart failure.
Summary of Interactions with Vitamins, Herbs, and Foods
In some cases, an herb or supplement may appear in more than one category, which may seem contradictory. For clarification, read the full article for details about the summarized interactions.
 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 |
An asterisk (*) next to an item in the summary indicates that the interaction is supported only by weak, fragmentary, and/or contradictory scientific evidence.
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 taking ACE inhibitors could cause life-threatening problems.8 Therefore, people should consult their healthcare practitioner before supplementing additional potassium and should have their blood levels of potassium checked periodically while taking ACE inhibitors.
Zinc
In a study of 34 people with hypertension, six months of captopril or enalapril (ACE inhibitors related to quinapril) treatment led to decreased zinc levels in certain white blood cells,9 raising concerns about possible ACE inhibitor–induced zinc depletion.
While zinc depletion has not been reported with quinapril, until more is known, it makes sense for people taking quinapril long term to consider, as a precaution, taking a zinc supplement or a multimineral tablet containing zinc. (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.10
Interactions with Foods and Other Compounds
Food
High-fat meals may reduce quinapril absorption;11 otherwise, quinapril may be taken with or without food.12
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, Zaidenstein R, Dishi V, et al. Effects of captopril and enalapril on zinc metabolism in hypertensive patients. J Am Coll Nutr 1998;17:75–8.
10. Lee SC, Park SW, Kim DK, et al. Iron supplementation inhibits cough associated with ACE inhibitors. Hypertension 2001;38:166–70.
11. Threlkeld DS, ed. Diuretics and Cardiovasculars, Antihypertensives, Angiotensin Converting Enzyme Inhibitors. In Facts and Comparisons Drug Information. St. Louis, MO: Facts and Comparisons, Apr 1998, 165q.
12. Ferry JJ, Horvath AM, Sedman AJ, et al. Influence of food on the pharmacokinetics of quinapril and its active diacid metabolite, CI-928. J Clin Pharmacol 1987;27:397–9.
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2006-09-07
