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# Folic Acid ## Overview Folic acid (vitamin B9) is a water-soluble B vitamin essential for DNA synthesis, repair, and erythropoiesis. It is a synthetic form of folate used for therapeutic supplementation. ## Primary Indications * Treatment of folate-deficiency anemia. * Prevention of neural tube defects (NTDs) in pregnancy. * Prophylaxis in patients with high folate turnover (e.g., hemolytic anemia, dialysis) or drug-induced deficiency (e.g., methotrexate). ## Adult Dosing * **Folate-Deficiency Anemia:** 1 mg daily. Severe cases may require up to 5 mg daily. * **Pregnancy/Lactation (Prevention of NTDs):** 0.4–0.8 mg daily. High-risk patients (history of NTD pregnancy) may require 4–5 mg daily starting 1 month before conception and through the first trimester. * **Maintenance:** 0.4 mg daily. * **Methotrexate-induced toxicity:** 1–5 mg/day (varies by regimen and local protocol). ## Pediatric Dosing * **Maintenance:** * Infants: 0.1 mg daily. * Children 1–3 years: 0.15 mg daily. * Children 4–8 years: 0.2 mg daily. * Children >9 years: 0.4 mg daily. * **Deficiency Treatment:** 0.5–1 mg daily. Refer to specialist/local clinical protocols for severe pediatric malabsorption cases. ## Dose Adjustments * **Renal Impairment:** No standard adjustment required; however, patients on dialysis lose folate and require daily supplementation. * **Hepatic Impairment:** No adjustments required. ## Contraindications * Hypersensitivity to any component of the formulation. * Undiagnosed anemia (specifically vitamin B12 deficiency). **Warning:** Folic acid can mask symptoms of B12 deficiency (pernicious anemia) while allowing neurological damage to progress. ## Adverse Effects Generally well-tolerated. Rare reports include: * Gastrointestinal: Bloating, nausea, abdominal pain. * Dermatologic: Allergic rash, pruritus. * Hypersensitivity: Anaphylaxis (very rare). ## Key Drug Interactions * **Methotrexate:** Folic acid can reduce the efficacy of methotrexate when used for oncologic or autoimmune conditions. * **Anticonvulsants (Phenytoin, Phenobarbital, Primidone):** Folic acid may decrease serum concentrations of these medications, potentially increasing seizure risk. * **Sulfonamides:** May inhibit folate absorption or metabolism. ## Monitoring * **Baseline:** Complete blood count (CBC) and serum B12 concentrations to rule out pernicious anemia. * **Therapeutic:** Monitor hemoglobin and hematocrit indices to assess treatment response. ## Clinical Pearls * Never treat anemia with folic acid alone without excluding vitamin B12 deficiency. * Supplementation is most effective for NTD prevention if initiated at least one month preconception. * Parenteral administration is rarely necessary unless severe malabsorption is present. * Folic acid is photosensitive; protect storage from light. *** **Educational Disclaimer:** This information is for educational purposes only. Clinical practice guidelines and local protocols vary significantly. Always verify specific dosing, safety profiles, and therapeutic indications using current, institutional-approved drug references (e.g., Lexicomp, Micromedex) or your organization’s pharmacy department before prescribing or administering medication.