Water-Soluble (B9)·Vitamins & Minerals

Folic acid

Folate deficiency megaloblastic anemia, prevention of neural tube defects, adjunct to Methotrexate therapy

VITAMINMegafol0.5 mg tabletUNSCHEDULEDTGA

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At a glance

Dose

5 mg/day

Half-life

Hours

Caution: MTX Rescue

MANDATORY

Pregnancy

NEURAL TUBE

Cautions

Avoid / Cautions

Undiagnosed megaloblastic anemia (Must check B12 levels first to rule out pernicious anemia). Pregnancy Category A. Mandatory requirement.

Where it stands

Rapid Summary

Overview

Vitamin B9. Synthetic folate. Absolutely essential for DNA synthesis, red blood cell formation, and fetal neural tube development.

Clinical Focus

Essential before and during early pregnancy for neural tube defect prevention; exclude or treat vitamin B12 deficiency before high-dose folate for megaloblastic anaemia.

Bottom Line

Folic acid is critical for neural tube defect prevention in pregnancy and managing folate deficiency, but must never be given alone if B12 deficiency is not excluded as it can mask and worsen neurological damage.

Formulation & Access

Brand Names

Megafol

Oral Routes

Tablets (0.5 mg, 5 mg).

Parenteral

Ampoules for IV / IM (Rarely used, oral absorption is near 100%).

Prescribing & PBS

Over The Counter (OTC).

Indications & Use

Primary

TGA

Folate deficiency megaloblastic anemia, prevention of neural tube defects, adjunct to Methotrexate therapy.

Clinical Place

Foundational supplement in antenatal care and rheumatology.

Quick reference

Class & Role

Water-Soluble (B9) — Vitamin B9.

Route / Formulation

Tablets (0.5 mg, 5 mg). (Megafol)

Usual Dose & Max

PO 5 mg OD for 4 months. Max 5 mg/day.

Key Indication Doses

Megaloblastic Anemia: PO 5 mg OD for 4 months. Pregnancy Prophylaxis: PO 0.5 mg OD (Start 1 month before conception). Give 5 mg OD if high risk (e.g., on Valproate/Carbamazepine). Methotrexate Rescue: PO 5 mg ONCE WEEKLY. Must be taken 1 to 2 days *after* the Methotrexate dose.

Best Uses

Key Risks

Neurological: Can mask Vitamin B12 deficiency. If high-dose folate is given to a B12-deficient patient, the anemia improves, but the irreversible neurological damage (subacute combined degeneration of the cord) silently accelerates. Systemic: Extremely benign profile. Virtually zero toxicity as excess is peed out.

Key Interactions

Methotrexate. Folate replaces the exact compound Methotrexate is trying to starve the body of. If taken on the *same day*, the Folate will cancel out the Methotrexate, causing a severe arthritis flare. Must be staggered. Phenytoin and Barbiturates lower folate levels, and paradoxically, giving folate can lower Phenytoin levels, risking seizures.

Monitoring

Always check both Serum Folate AND Vitamin B12 levels together before initiating treatment. Monitor FBC.

Clinical Pearl

Women taking Valproate or Carbamazepine for epilepsy are at a massively increased risk of having a baby with spina bifida (due to folate depletion). They MUST be on the high-dose 5 mg folic acid tablet, not the standard 0.5 mg pregnancy multivitamin.

Access

Megafol0.5 mg tablet

Brand: Megafol
Formulation: Tablets (0.5 mg, 5 mg).

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