CHAPTER 3-33: FOLIC ACID

INTRODUCTION

1. Pharmacology. Folic acid is a B-complex vitamin that is essential for protein synthesis and erythropoiesis. In addition, the administration of folate to patients with methanol poisoning may enhance the conversion of the toxic metabolite formic acid to carbon dioxide and water, based on studies in folate-deficient primates. Note: Folic acid requires metabolic activation and may not be effective for the treatment of acute poisoning by dihydrofolate reductase inhibitors (eg, methotrexate and trimethoprim). Leucovorin is the proper agent in these situations.

2. Indications. Adjunctive treatment for methanol poisoning and possibly ethylene glycol poisoning.

3. Contraindications. No known contraindications.

4. Adverse effects

   1. Rare allergic reactions have been reported after intravenous administration.

   2. Use in pregnancy. FDA Category A (Introduction). Folic acid is a recommended supplement.

5. Drug or laboratory interactions. This agent may decrease phenytoin levels by enhancing its metabolism.

6. Dosage and method of administration. The dose required for methanol (or ethylene glycol) poisoning is not established, although 1–2 mg/kg (typical doses are 50–70 mg IV) every 4–6 hours has been recommended. Folic acid should be readministered following hemodialysis as it is readily removed by the procedure.

7. Formulations

   1. Parenteral. Sodium folate 5 mg/mL, 10-mL vials.

   2. Suggested minimum stocking levels to treat a 100-kg adult for the first 8 hours and 24 hours: folate sodium, first 8 hours: 100–200 mg or 2–4 vials (5 mg/mL, 10 mL each); first 24 hours: 300–600 mg or 6–12 vials (5 mg/mL, 10 mL each).