Folic Acid

DESCRIPTION Folic acid, N-[ p -[[(2-amino-4- hydroxy-6-pteridinyl) methyl]- amino] benzoyl]-Lglutamic acid, is a B complex vitamin containing a pteridine moiety linked by a methylene bridge to para -aminobenzoic acid, which is joined by a peptide linkage to glutamic acid. Conjugates of folic acid are present in a wide variety of foods, particularly liver, kidneys, yeast, and leafy green vegetables. Commercially available folic acid is prepared synthetically. Folic acid, USP occurs as a yellow or yellowish-orange, odorless, crystalline powder. It is very slightly soluble in water and insoluble in alcohol. Folic acid, USP is readily soluble in dilute solutions of alkali hydroxides and carbonates, and solutions of the drug may be prepared with the aid of sodium hydroxide or sodium carbonate, thereby forming the soluble sodium salt of folic acid (sodium folate). Aqueous solutions of folic acid are heat sensitive and rapidly decompose in the presence of light and/or riboflavin; solutions should be stored in a cool place protected from light. The structural formula of folic acid is as follows: C 19 H 19 N 7 O 6 M.W. 441.40 Each tablet, for oral administration, contains 1 mg folic acid, USP. Folic acid tablets, USP 1 mg contain the following inactive ingredients: lactose monohydrate, microcrystalline cellulose, sodium starch glycolate, Type A and stearic acid. 1

INDICATIONS AND USAGE Folic acid is effective in the treatment of megaloblastic anemias due to a deficiency of folic acid (as may be seen in tropical or nontropical sprue) and in anemias of nutritional origin, pregnancy, infancy, or childhood.

CONTRAINDICATIONS Folic acid is contraindicated in patients who have shown previous intolerance to the drug.

WARNING Administration of folic acid alone is improper therapy for pernicious anemia and other megaloblastic anemias in which vitamin B 12 is deficient.

ADVERSE REACTIONS Allergic sensitization has been reported following both oral and parenteral administration of folic acid. Folic acid is relatively nontoxic in man. Rare instances of allergic responses to folic acid preparations have been reported and have included erythema, skin rash, itching, general malaise, and respiratory difficulty due to bronchospasm. One patient experienced symptoms suggesting anaphylaxis following injection of the drug. Gastrointestinal side effects, including anorexia, nausea, abdominal distention, flatulence, and a bitter or bad taste, have been reported in patients receiving 15 mg folic acid daily for 1 month. Other side effects reported in patients receiving 15 mg daily include altered sleep patterns, difficulty in concentrating, irritability, overactivity, excitement, mental depression, confusion, and impaired judgment. Decreased vitamin B 12 serum levels may occur in patients receiving prolonged folic acid therapy. In an uncontrolled study, orally administered folic acid was reported to increase the incidence of seizures in some epileptic patients receiving phenobarbital, primidone, or diphenylhydantoin. Another investigator reported decreased diphenylhydantoin serum levels in folate-deficient patients receiving diphenylhydantoin who were treated with 5 mg or 15 mg of folic acid daily.

OVERDOSAGE Except during pregnancy and lactation, folic acid should not be given in therapeutic doses greater than 0.4 mg daily until pernicious anemia has been ruled out. Patients with pernicious anemia receiving more than 0.4 mg of folic acid daily who are inadequately treated with vitamin B 12 may show reversion of the hematologic parameters to normal, but neurologic manifestations due to vitamin B 12 deficiency will progress. Doses of folic acid exceeding the Recommended Dietary Allowance (RDA) should not be included in multivitamin preparations; if therapeutic amounts are necessary, folic acid should be given separately.