folic acid: clinical use

Prescribing considerations

• Establish the cause of macrocytosis or megaloblastic anaemia and assess cobalamin status before folic-acid monotherapy.
• Investigate persistent malabsorption, haemolysis, poor nutrition, medicine-related deficiency or an inadequate response.
• In pregnancy, distinguish routine supplementation from prescribed treatment for deficiency or increased neural-tube-defect risk.
• Review antiepileptic and antifolate medicines.
• Check product-specific excipients and suitability when selecting a tablet or oral solution.

Contraindications and cautions

• Hypersensitivity to folic acid or a product excipient.
• Do not use folic acid alone for untreated vitamin B12 deficiency or pernicious anaemia because blood-count improvement can mask continuing neurological injury.
• Avoid in folate-dependent tumours or malignant disease unless folate-deficient megaloblastic anaemia is an important complication.
• Lexpec is contraindicated in hydroxybenzoate hypersensitivity; excipient restrictions differ by product.

Monitoring

• Consider full blood count, folate and vitamin B12 assessment and investigation of the underlying cause before treatment.
• Assess clinical and haematological response; review the diagnosis if the expected response is absent.
• The Colonis product information additionally advises considering potassium and iron or ferritin status.
• Monitor seizure control when correcting folate deficiency in someone taking an antiepileptic.

Clinical pharmacology

Folic acid is absorbed from the gastrointestinal tract and converted to active reduced folates involved in purine, pyrimidine and methionine synthesis. Excess folate is mainly eliminated in urine, and folic acid is removed by haemodialysis.

Formulation and product differences

• Selected products include a tablet and oral solutions of different concentrations; liquid volumes are not interchangeable.
• The Colonis solution includes a graduated oral syringe and bottle adaptor and contains sodium methyl parahydroxybenzoate; it is essentially sodium-free at the stated unit volume.
• Lexpec contains hydroxybenzoates, propylene glycol, sodium and strawberry flavour; neonatal propylene-glycol exposure requires particular attention.
• The selected tablet contains lactose and sucrose, which may matter in specific hereditary carbohydrate-intolerance disorders.
• Storage and in-use shelf life differ; follow the individual packaging and leaflet.

Oral solution

Route: Oral

Strengths: 1 mg/mL, 2.5 mg/5 mL

Tablet

Route: Oral

Strengths: 5 mg