Numerous multivitamin preparations are marketed, with little standardization of formulas. Useful multivitamin preparations should contain only essential vitamins (those for which there is a recommended daily dietary allowance [RDA]). (See Dosage and Administration.) Preparations containing iron and/or calcium supplements may be useful in some patients (e.g., pregnant or lactating women) but other essential minerals are usually obtained from the diet. The addition of agents such as liver, yeast, and wheat germ to vitamin preparations offers no advantage over pure chemical ingredients, and inclusion of nonessential agents such as choline, bioflavonoids, inositol, betaine, lecithin, and methionine is unwarranted. Combinations of vitamins and other drugs such as hormones are irrational and should not be used.
Vitamin Deficiencies 
When a single vitamin deficiency is evident, other vitamin deficiencies (clinical or subclinical) often accompany it. Therapeutic multivitamin preparations (see Dosage and Administration) may, therefore, be useful in these patients. Therapeutic multivitamins may also be indicated in pathologic conditions in which nutritional requirements are greatly increased (e.g., alcoholism, hyperthyroidism, severe illness or injury, cachexia) or in conditions in which absorption, utilization, or excretion of vitamins is abnormal (including malabsorption syndromes). Therapeutic multivitamins should not be used as dietary supplements, and medical supervision is important when these preparations are given.
Dietary Supplementation
An adequate amount of vitamins and minerals usually is obtained from a well-balanced diet, and healthy individuals consuming such a diet can expect no benefit from additional vitamins. Supplementary multivitamin preparations (see Dosage and Administration) may be used to assure an adequate supply of vitamins in patients with poor dietary habits or temporarily decreased dietary intake. Preparations containing 100-150% of the RDA may be useful in patients with severely restricted food intake. Whenever possible, poor dietary habits should be corrected. Vitamin and mineral supplements may be required to meet temporarily increased demand (e.g., during pregnancy and lactation) or to ensure proper growth of infants and children. Patients undergoing hemodialysis may require vitamin and mineral supplements to compensate for increased losses.
The vitamin combination chosen should fit the needs of the individual patient. In selecting a multivitamin, it should be remembered that increased intake of certain vitamins or nutrients increases the demand for other vitamins. Also, some vitamins (especially vitamins A and D) and many minerals may be toxic in large doses, and dosage of multivitamin preparations containing these agents should take the patient's dietary intake into account. There is a potential danger in administering more than the RDA of folic acid to patients with undiagnosed anemia because folic acid may obscure the diagnosis of pernicious anemia by alleviating hematologic manifestations of the disease while allowing neurologic complications to progress.
Administration
Vitamins are usually administered orally; however, the drugs may be given parenterally in patients in whom oral administration is not feasible, including those receiving total parenteral nutrition. For IV administration, vitamins should be diluted according to the manufacturers' recommendations. Multivitamin injections are reportedly incompatible with IV solutions containing various drugs. Published data are too varied and/or limited to permit generalizations, and specialized references should be consulted for specific compatibility information.
Dosage
Recommended Dietary Allowances
The US Food and Drug Administration has established recommended daily allowances (US RDA) which are used in nutrition labeling. The US RDA is the amount of a vitamin or mineral which is believed to be necessary to maintain health in broad age groups of humans. These should not be confused with the recommended daily dietary allowances (RDA) of the Food and Nutrition Board of the National Research Council. The RDA is the amount of a nutrient which will maintain good nutrition in practically all healthy individuals in the US; the RDA is more specific in relation to age and sex than is the US RDA. Dietary intake of less than the RDA does not necessarily indicate deficiency or substandard nutrition since the RDA allows for large individual variation and is greater than the minimum amount that will prevent deficiency.
Supplementary (prophylactic) multivitamin preparations may reasonably contain 50-150% of the RDA of vitamins and minerals (except the amount of vitamin D and folic acid should not exceed the RDA). Therapeutic multivitamins may reasonably contain 3-5 times the RDA (except the amount of vitamin D and folic acid should not exceed the RDA). Vitamin A dosage should also be limited to avoid hypervitaminosis A. If the required dose of a specific vitamin greatly exceeds the RDA, that vitamin should be given separately.
New Dietary Requirements
The National Academy of Sciences (NAS) has issued a comprehensive set of Recommended Dietary Allowances (RDAs) as reference values for dietary nutrient intakes since 1941.100 In late 1997, the NAS Food and Nutrition Board (part of the Institute of Medicine [IOM]) announced that they would begin issuing revised nutrient recommendations that would replace RDAs with Dietary Reference Intakes (DRIs).100 At the time the 2002 edition of AHFS Drug Information went to press, NAS had issued the first, second, third, and fourth sets of such revised recommendations, which are for calcium, fluorides, magnesium, phosphorus, vitamin D, folic acid, niacin, pantothenic acid, pyridoxine, riboflavin, thiamine, vitamin B12, vitamin E, vitamin C, vitamin A, vitamin K, iron, and other micronutrients.100,104,105,106 (See the monographs on Calcium Salts 40:12, Fluorides 92:28, the Vitamin D Analogs General Statement 88:16, those in Vitamin B Complex section 88:08, Vitamin C 88:12, and Vitamin E 88:20, vitamin A 88:04, Phytonadione 88:24, and Iron Preparations 20:04.04.) DRIs are reference values that can be used for planning and assessing diets for healthy populations and for many other purposes and that encompass the Estimated Average Requirement (EAR), the Recommended Dietary Allowance (RDA), the Adequate Intake (AI), and the Tolerable Upper Intake Level (UL).100 DRIs apply to the healthy general population, with RDAs and AIs defining the nutrient levels that should decrease the risk of developing a condition related to an inadequate intake of the given nutrient and associated with a negative functional outcome.100 Intake at the level of the RDA or AI would not necessarily replete the nutrient in undernourished individuals nor would it be adequate for disease states marked by increased requirements of the nutrient.100
The EAR is the nutrient intake value that is estimated to meet the requirement defined by a specific indicator of adequacy (e.g., maximum calcium retention) in 50% of individuals in a life-stage and gender group.100 In the past, recommended nutrient intake values (e.g., RDAs) often were based principally on levels needed to prevent deficiency, whereas EARs consider these levels as well as levels associated with disease risk reduction (e.g., osteoporosis).100,101 The RDA currently is defined as the daily dietary intake level that is sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in a given life-stage and gender group; RDAs apply to individuals not to groups, and the EAR serves as the basis for establishing the RDA.100 Although RDAs also previously were defined as the level of intake of essential nutrients that, on the basis of scientific knowledge, were judged to be adequate to meet the known nutrient needs of practically all healthy individuals,101 the current methods for establishing RDAs differ from those used in the past and, together with EARs and other reference values, address increased understanding of both population and individual nutrient needs.100
The RDA for a given nutrient, in a prescriptive sense, is the goal for dietary intake in individuals.100 If data are insufficient or too controversial to establish an RDA for a given life-stage group, an AI will be used instead.100 AIs are used when scientific evidence is insufficient to calculate a given EAR, which is needed for establishing the RDA.100 AIs are based on observed or experimentally determined approximations of the average nutrient intake, by a defined population or subgroup, that appears to sustain a defined nutritional state (e.g., usual circulating nutrient levels, nutrient levels for normal growth).100 In the absence of definitive data needed to establish the EAR and RDA, the AI may be used as the goal for nutrient intake in healthy individuals; however, the AI should not be considered equivalent to the RDA, and in some cases actually may exceed the RDA that eventually gets established.100
Over time, the current RDAs for other nutrients will become replaced with new DRIs.100 In the interim, the most recent set of RDAs issued by NAS in 1989 can be followed for those nutrients for which the new DRIs have not yet been finalized and issued.100
For information on specific vitamins, see the monographs in 88:00.
AHFS® Drug Information. © Copyright, 1959-2024, Selected Revisions April 1, 2006. American Society of Health-System Pharmacists, Inc., 4500 East-West Highway, Suite 900, Bethesda, MD 20814.
Only references cited for selected revisions after 1984 are available electronically.
100. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes of the Food and Nutrition Board, Institute of Medicine, National Academy of Sciences. Dietary reference intakes for calcium, phosphorus, magnesium, vitamin D, and fluoride. Washington, DC: National Academy Press; 1997. (Uncorrected proofs.)
101. National Research Council Subcommittee on the Tenth Edition of the RDAs. Recommended dietary allowances. 10th ed. Washington, DC: National Academy Press; 1989.
102. Anon. Lactic acidosis traced to thiamine deficiency related to nationwide shortage of multivitamins for total parenteral nutrition-United States, 1997. MMWR Morb Mortal Wkly Rep . 1997; 46:523-8. [PubMed 9191033]
103. American Society for Parenteral and Enteral Nutrition (ASPEN). Multivitamin shortage-Update #17: fatality reported. Press release. 1997 Jul 21.
104. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes of the Food and Nutrition Board, Institute of Medicine, National Academy of Sciences. Dietary reference intakes for thiamin, riboflavin, niacin, vitamin B6, folate, vitamin B12, pantothenic acid, biotin, and choline. Washington, DC; National Academy Press; 1998. Prepublication copy uncorrected proofs.)
105. Committee on the Scientific Evaluation of Dietary Reference Intakes of the Food and Nutrition Board, Institute of Medicine, National Academy of Sciences. Dietary reference intakes for Vitamin C, Vitamin E, selenium, and carotenoids. Washington, DC; National Academy Press; 2000.
106. Standing Committee on the Scientific Evaluation of Dietary Reference Intakes of the Food and Nutrition Board, Institute of Medicine, National Academy of Sciences. Dietary reference intakes for vitamin A, vitamin K, arsenic, boron, chromium, copper, iodine, iron, manganese, molybdenum, nickel, silicon, vanadium, and zinc. Washington, DC: National Academy Press; 2001. (Prepublication copy uncorrected proofs.)