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Mechanism of Action
US Drug Names
Follow directions for specific product chosen, as per its package label. Usual dose for most products is 1 tablet PO once per day. Use before conception (even just 1 month before fertilization) appears to have benefits, including the reduction of nausea/vomiting in early pregnancy per the American College of Gynecology and Obstetrics (ACOG).
1 tablet or dose, as defined on the product label, PO per day.
Safety and efficacy have not been established.
Do not use.
Specific guidelines for dosage adjustments in hepatic impairment are not available; it appears that no dosage adjustments are needed.
Specific guidelines for dosage adjustments in renal impairment are not available; it appears that no dosage adjustments are needed.
Prenatal multivitamins and minerals products consist of a variety of vitamins and minerals intended to be taken before, during and after pregnancy and may also be used postpartum in lactating and non-lactating mothers. Many vitamins and minerals, such as folic acid, iron, and calcium, are all vital for proper fetal growth and development. The available preparations may vary depending on the manufacturer and nutritional focus (e.g., some preparations may contain DHA or a higher iron content). Some products contain a stool softener to help prevent constipation. All contain folic acid, a vitamin vital in the prevention of neural tube defects, particularly in the first trimester; many prenatal supplements contain 1 mg of this important vitamin. Women of childbearing potential should ensure adequate dietary intake of folic acid pre-conception, and are advised to start taking folate supplementation several weeks before desiring to conceive and to continue taking them through the first 12 weeks of pregnancy or longer. ACOG guidelines state that taking prenatal vitamins for 1 month before conception may help reduce the incidence and severity of nausea/vomiting of pregnancy.
For storage information, see the specific product information within the How Supplied section.
Common gastrointestinal complaints when taking prenatal multivitamins and minerals include nausea, dyspepsia, constipation or gastric irritation (gastritis). Some effects can be reduced or circumvented by taking the vitamin with a meal and with plenty of liquid to reduce stomach upset or nausea, or adding a stool softener to relieve complaints of constipation. Stool discoloration (darkening) may be noted by patients taking supplements containing iron.
Allergic sensitization has been reported following both oral and parenteral administration of folic acid. Allergic reactions could potentially occur due to other components of prenatal multivitamins and minerals products as well. Be alert for rare reactions like dyspnea, rash (unspecified), pruritus, or urticaria.
NOTE: This monograph discusses prenatal multivitamin and mineral products when taken as marketed. Clinicians may wish to refer to individual component monographs for more information regarding individual supplements contained in the products of interest.
Prenatal multivitamins and minerals products are contraindicated in patients hypersensitive to any particular product components. Carefully review product components prior to selecting a particular product for a given patient.
Prenatal multivitamins and minerals preparations are not intended for ingestion by pre-pubescent children or adolescent males. The supplement is intended for females of child-bearing potential only. Accidental overdose of iron-containing products is a leading cause of fatal poisoning in children and infants under 6 years of age. Keep this product out of reach of children and infants. In case of accidental exposure via ingested overdose, call a doctor or poison control center immediately.
Certain prenatal multivitamins and minerals products contain fish oils or omega-3-fatty acids. Ingestion of more than 3 grams of omega-3 fatty acids (such as DHA) per day has been shown to have potential antithrombotic effects, including an increased bleeding time and International Normalized Ratio (INR). Administsration of omega-3 fatty acids should generally be avoided in patients taking anticoagulant therapy and in those known to have an inherited or acquired predisposition to bleeding.
Prenatal multivitamins and minerals are generally recognized as safe (GRAS) for meeting nutritional requirements of females during pre-conception, pregnancy and breast-feeding. No particular precautions are advised. Use before conception (even just 1 to 3 months before fertilization) appears to have benefits, including the reduction of neural tube defects in the fetus, and reduction in symptoms of nausea/vomiting in early pregnancy.   
Folic acid alone is improper therapy in the treatment of pernicious anemia and other vitamin B12 deficiency megaloblastic anemia where vitamin B12 is deficient. Folic acid in doses above 1 mg daily may obscure pernicious anemia in that hematologic remission can occur while neurological manifestations progress.
Those suffering from hereditary/genetic hemochromatosis or hemochromatosis due to secondary iron overload (e.g., as in iron-loading anemias such as thalassemia or sideroblastic anemia) need to avoid prenatal multivitamins and minerals containing iron supplements. Hemochromatosis causes the body to lose its ability to regulate the amount of iron that is absorbed, leading to excess iron absorption and tissue storage. Massive deposition of iron (hemosiderosis) in parenchymal tissues in these conditions may damage the liver, heart, pancreas and other tissues. Porphyria cutanea tarda (PCT) is sometimes associated with parenchymal iron deposits; patients with PCT should avoid iron supplements unless prescribed by a physician. Excess iron supplementation in patients with PCT can contribute to hepatic uroporphinogen decarboxylase deficiency, but the mechanism is not clear. Some patients with chronic hepatic disease may have hemochromatosis or moderate iron overload in hepatic tissues. The liver is one of the main storage sites for iron, and advanced chronic liver disease may result in excess storage iron in the liver. Thus patients with hepatic disease should receive iron supplementation with caution and only under the direction of a health care prescriber.
For specific mechanisms of action, please refer to individual monographs discussing the specific vitamin, mineral or supplement components.
Prenatal multivitamins and minerals are administered orally. The products contain varying components of fat-soluble and water-soluble vitamins and important minerals.
Affected Cytochrome P450 (CYP450) enzymes and drug transporters: Varies
Some prenatal vitamin and mineral products contain other dietary supplements and herbs,some of which might affect drug metabolism and transport. Specific pharmacokinetic information is not available for these combination products. Clinicians are advised to review individual product components and consider review of pharmacokinetic information found on individual monographs for more information.
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