Please check your internet connection and try again.
# Folic Acid
## Overview
Folic acid (vitamin B9) is a water-soluble B-complex vitamin essential for DNA synthesis, erythropoiesis, and amino acid metabolism. Synthetic folic acid is more stable and has higher bioavailability than naturally occurring food folates.
## Primary Indications
* Treatment of folate deficiency megaloblastic anemia.
* Prevention of neural tube defects (NTDs) in pregnancy.
* Prophylaxis in chronic hemolytic anemias or dialysis.
* Adjunct therapy with methotrexate (to reduce gastrointestinal/hematologic toxicity).
## Adult Dosing
* **Folate Deficiency:** 0.4–1 mg daily. Severe cases may require up to 5 mg daily.
* **Pregnancy (Prevention of NTDs):** 0.4–0.8 mg daily, starting ideally 1 month before conception and throughout the first trimester. High-risk patients (history of NTD-affected pregnancy, anti-epileptic use) may require 4–5 mg daily per clinical protocol.
* **Methotrexate Adjunct:** 1–5 mg daily (non-dose day) or 5–10 mg weekly following methotrexate doses, depending on institutional oncology protocols.
## Pediatric Dosing
* **Folate Deficiency:**
* Infants: 0.1 mg daily.
* Children 1–11 years: 0.2–0.3 mg daily.
* Children ≥12 years: 0.4 mg daily.
* Maintenance: 0.1–0.4 mg daily based on age.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No specific dose adjustment defined; however, those on chronic dialysis should receive supplemental folate (typically 1–5 mg/day) as it is readily cleared by hemodialysis.
## Contraindications
* **Untreated Vitamin B12 Deficiency:** Do not use as monotherapy for pernicious anemia or undiagnosed megaloblastic anemia. Folic acid may mask the hematologic symptoms of B12 deficiency while allowing irreversible neurological damage to progress.
## Adverse Effects
* Generally well-tolerated.
* Rare: Allergic reactions (rash, pruritus, dyspnea).
* Gastrointestinal: Nausea, abdominal distension, bitter taste (with high doses).
## Key Drug Interactions
* **Methotrexate:** Folic acid may decrease the efficacy of methotrexate in treating rheumatoid arthritis or psoriasis.
* **Anticonvulsants (Phenytoin, Carbamazepine, Valproic Acid):** Folic acid may lower serum levels of these agents, potentially increasing seizure frequency.
* **Sulfonamides/Pyrimethamine:** May interfere with folate metabolism.
## Monitoring
* Monitor hemoglobin/hematocrit and reticulocyte count.
* Monitor folate and B12 levels.
* Ensure vitamin B12 deficiency is ruled out before initiating high-dose folate therapy.
## Clinical Pearls
* The "ceiling" for folic acid intake is not strictly defined, but chronic high-dose supplementation (≥1 mg/day) may mask B12 deficiency.
* Folic acid is photosensitive; protect containers from light.
* Dietary sources (leafy greens, fortified grains) are preferred for general health maintenance.
***
**Educational Disclaimer:** This information is for educational purposes only. Clinical protocols vary by institution. Always verify dosages, contraindications, and drug interactions against current primary literature, institution-specific guidelines, and the official manufacturer-provided product monograph before prescribing or administering medication.
