If you are being treated with any of the following medications, you should not use carnitine without first talking to your health care provider.
AZT -- In a laboratory study, L-carnitine supplements protected muscle tissue against toxic side effects from AZT, a medication used to treat HIV and AIDS. More studies are needed to know whether L-carnitine would have the same effect in people.
Doxorubicin -- Treatment with L-carnitine may protect heart cells against the toxic side effects of doxorubicin, a chemotherapy medication used to treat cancer, without making the medication any less effective. Always talk to your oncologist before using any complementary or alternative therapy with chemotherapy.
Isotretinoin (Accutane) -- Accutane, a strong medication used for severe acne, can cause liver problems, as measured by a blood test, as well as high cholesterol and muscle pain and weakness. These symptoms are like those seen with carnitine deficiency. Researchers in Greece showed that a large group of people who had side effects from Accutane got better when taking L-carnitine compared to those who took a placebo.
Thyroid hormone -- Carnitine may stop thyroid hormone from getting into cells, and theoretically may make thyroid hormone replacement less effective. If you take thyroid replacement hormone, talk to your health care provider before taking carnitine.
Valproic acid (Depakote) -- The anti-seizure medication valproic acid may lower blood levels of carnitine. Taking L-carnitine supplements may prevent any deficiency and may also reduce the side effects of valproic acid. However, taking carnitine may increase the risk of seizures in people with a history of seizures.
Benvenga S, Ruggieri RM, Russo A, Lapa D, Campenni A, Trimarchi F. Usefulness of L-carnitine, a naturally occurring peripheral antagonist of thyroid hormone action, in iatrogenic hyperthyroidism: a randomized, double-blind placebo-controlled clinical trial. J Clin Endocrinol Metab. 2001;86(8):3579-3594.
Berni A, Meschini R, Filippi S, Palitti F, De Amicis A, Chessa L. L-carnitine enhances resistance to oxidative stress by reducing DNA damage in Ataxia telangiectasia cells. Mutat Res. 2008;650(2):165-74.
Biagiotti G, Cavallini G. Acetyl-L-carnitine vs tamoxifen in the oral therapy of Peyronie's disease: a preliminary report. BJU Int. 2001;88(1):63-67.
Carrero JJ, Grimble RF. Does nutrition have a role in peripheral vascular disease? Br J Nutr. 2006 Feb;95(2):217-29. Review.
Cavallini G, Modenini F, Vitali G, et al. Acetyl-L-carnitine plus propionyl-L-carnitine improve efficacy of sildenafil in treatment of erectile dysfunction after bilateral nerve-sparing radical retropubic prostatectomy. Urology. 2005;66:1080-1085.
Cruciani RA, Dvorkin E, Homel P, Malamud S, Culliney B, Lapin J, Portenoy RK, Esteban-Cruciani N. Safety, tolerability and symptom outcomes associated with L-carnitine supplementation in patients with cancer, fatigue, and carnitine deficiency: a phase I/II study. J Pain Symptom Manage. 2006 Dec;32(6):551-9.
Custer J, Rau R. Johns Hopkins:The Harriet Lane Handbook, 18th ed. Philadelphia, PA; Elsevier Mosby; 2008.
Dyck DJ. Dietary fat intake, supplements, and weight loss. Can J Appl Physiol. 2000;25(6):495-523.
Fugh-Berman A. Herbs and dietary supplements in the prevention and treatment of cardiovascular disease. Prev Cardiology. 2000;3:24-32.
Head KA. Peripheral neuropathy: pathogenic mechanisms and alternative therapies. Altern Med Rev. 2006 Dec;11(4):294-329. Review.
Hiatt WR, Regensteiner JG, Creager MA, Hirsch AT, Cooke JP, Olin JW, et al. Propionyl-L-carnitine improves exercise performance and functional status in patients with claudication. Am J Med. 2001;110(8):616-622.
Lynch KE, Feldman HI, Berlin JA, Flory J, Rowan CG, Brunelli SM. Effects of L-carnitine on dialysis-related hypotension and muscle cramps: a meta-analysis. Am J Kidney Dis. 2008;52(5):962-71.
Malaguarnera M, Cammalleri L, Gargante MP, Vacante M, Colonna V, Motta M. L-carnitine treatment reduces severity of physical and mental fatigue and increases cognitive functions in centurians: a randomized and controlled clinical trial. Am J Clin Nutr. 2007;86(6):1738-44.
Park M. Pediatric Cardiology for Practitioners, 5th ed. Philadelphia, PA: Mosby Elsevier, 2008.
Pettegrew JW, Levine J, McClure RJ. Acetyl-L-carnitine physical-chemical, metabolic, and therapeutic properties: relevance for its mode of action in Alzheimer's disease and geriatric depression. Mol Psychiatry. 2000;5:616-632.
Rathod R, Baig MS, Khandelwal PN, Kulkarni SG, Gade PR, Siddiqui S. Results of a single blind, randomized, placebo-controlled clinical trial to study the effect of intravenous L-carnitine supplementation on health-related quality of life in Indian patients on maintenance hemodialysis. Indian J Med Sci. 2006 Apr;60(4):143-53.
Sinclair S. Male infertility: nutritional and environmental considerations. Alt Med Rev. 2000;5(1):28-38.
Villani RG, Gannon J, Self M, Rich PA. L-carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women. Int J Sport Nutr Exerc Metab. 2000;10:199-207.
Volek J, et al. Effects of carnitine supplementation on flow-mediated dilation and vascular inflammatory responses to a high-fat meal in healthy young adults. Am J Cardiol. 2008;102(10).
Werbach MR. Nutritional strategies for treating chronic fatigue syndrome. Altern Med Rev. 2000;5(2):93-108.
Witte KK, Clark AL. Micronutrients and their supplementation in chronic cardiac failure. An update beyond theoretical perspectives. Heart Fail Rev. 2006 Mar;11(1):65-74. Review.
Witt KK, Clark AL, Cleland JG. Chronic heart failure and micronutrients. J Am Coll Cardiol. 2001;37(7):1765-1774.
Xue YZ, Wang LX, Liu HZ, Qi XW, Wang XH, Ren HZ. L-carnitine as an adjunct therapy to percutaneous coronary intervention for non-ST elevation myocardial infarction. Cardiovasc Drugs Ther. 2007;21(6):445-8.