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COMPLEMENTARY AND ALTERNATIVE MEDICINE

Safety Considerations and Potential Interactions of Vitamins: Should Vitamins Be Considered Drugs?

Assistant Director, Pediatric Research in Emergency Therapeutics (PRETx) Program; Post-Doctoral Fellow, Clinical Nutrition and Risk Factor Modification Center, St. Michael's Hospital, Toronto, ON, Canada

Sunita Vohra, MD MSc FRCPC

Director, Complementary and Alternative Research and Education (CARE) Program, Department of Pediatrics, Stollery Children's Hospital; Professor, Faculty of Medicine and Dentistry, and School of Public Health, University of Alberta, Edmonton, AB, Canada

Ran D Goldman, MD

Director, Pediatric Research in Emergency Therapeutics (PRETx) Program; Division Head and Medical Director, Division of Pediatric Emergency Medicine, BC Children's Hospital; Associate Professor, Department of Pediatrics, University of British Columbia; Senior Associate Clinician Scientist, Child & Family Research Institute (CFRI), Vancouver, BC, Canada

Reprints: Dr. Goldman, Division of Pediatric Emergency Medicine, BC Children's Hospital, Room K4-226, Ambulatory Care Building, 4480 Oak St., Vancouver, BC, V6H3V4, Canada, fax 604/875-2414, rgoldman{at}cw.bc.ca

OBJECTIVE: To examine adverse effects, adverse events, and potential interactions of vitamins in light of their current prevalence of use, and to discuss whether vitamins should be considered over-the-counter drugs or natural health products/dietary supplements.

DATA SOURCES: We performed a MEDLINE/PubMed search, explored 4 online databases (Medline Plus, Drug Digest, Natural Medicine Comprehensive Database, and the database of the University of Maryland), and examined reference lists of included studies published from 1966 through October 2009.

STUDY SELECTION AND DATA EXTRACTION: The studies were reviewed, with an emphasis on randomized controlled clinical trials. We included articles with the most clinically important information with regard to adverse events and interactions.

DATA SYNTHESIS: Vitamins are used by over one third of the North American population. Vitamins have documented adverse effects and toxicities, and most have documented interactions with drugs. While some vitamins (biotin, pantothenic acid, riboflavin, thiamine, vitamin B₁₂, vitamin K) have minor and reversible adverse effects, others, such as fat-soluble vitamins (A, E, D), can cause serious adverse events. Two water-soluble vitamins, folic acid and niacin, can also have significant toxicities and adverse events.

CONCLUSIONS: Our recommendation is that vitamins A, E, D, folic acid, and niacin should be categorized as over-the-counter medications. Labeling of vitamins, especially those intended for children and other vulnerable groups, should include information on possible toxicities, dosing, recommended upper intake limits, and concurrent use with other products. Vitamin A should be excluded from multivitamin supplements and food fortificants.

Key Words: complementary and alternative medicine, dietary supplements, drugs, vitamins

Published Online, December 29, 2009. www.theannals.com, DOI 10.1345/aph.1M238

This article has been cited by other articles:

				R. J. Marles Comment: Safety Considerations and Potential Interactions of Vitamins: Should Vitamins Be Considered Drugs? Ann. Pharmacother., July 1, 2010; 44(7): 1351 - 1351. [Full Text] [PDF]

				W. B. Grant, S. J. Whiting, and S. J. Genuis Comment: Safety Considerations and Potential Interactions of Vitamins: Should Vitamins Be Considered Drugs? Ann. Pharmacother., July 1, 2010; 44(7): 1351 - 1352. [Full Text] [PDF]