Class: Essential B Vitamin
Dosage Forms. Tablet: 0.4 mg, 0.8 mg, 1 mg; Capsule: 5 mg, 20 mg
Common FDA Label Indication, Dosing, and Titration.
1. Folic acid deficiency: Adults, 0.4-1 mg po daily; Children, infants, 0.1 mg/d; age under 4 y, up to 0.3 mg/d; age 4 y or older, 0.4-1 mg/d
2. Pregnancy, prophylaxis: 0.4-1 mg po daily
1. Hyperhomocysteinemia: 0.4-5 mg po daily
MOA. Folic acid is required for the conversion of deoxyuridylate to thymidylate, which is a rate limiting step in DNA synthesis, which presents clinically as macrocytic anemia when red blood cells are unable to extrude their nucleus.
Drug Characteristics: Folic Acid
Medication Safety Issues: Folic Acid
Drug Interactions: Folic Acid
Adverse Reactions: Folic Acid
Efficacy Monitoring Parameters. B12 and folic acid levels, normalization of MCV, normalization of Hgb, resolution of symptoms of anemia (fatigue, shortness of breath).
Toxicity Monitoring Parameters. Seek medical attention if severe shortness of breath, skin rash, or hives.
Key Patient Counseling Points. May require several weeks for maximum effect. Avoid alcohol as it inhibits the absorption of folic acid.
Clinical Pearls. Drugs that interfere with folate metabolism (methotrexate, hydroxyurea, pemetrexed) will cause an elevated MCV in the absence of vitamin B deficiency. Folic acid is given to women intending to become pregnant and in the early months of pregnancy to reduce the risk of neural tube defects and other birth defects (imperforate anus, cleft lip). Patients on pemetrexed receive folic acid to reduce pemetrexed toxicity. Enriched flour, bread, corn meal, pasta, rice, and other grain products have added folic acid to help decrease the risk of neural tube defects by increasing folic acid intake. Other foods which contain folic acid include dark green leafy vegetables, citrus fruits and juices, and lentils.