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Methyl donor (homocystinuria) Pregnancy: Data on a limited number of exposed pregnancies indicate no adverse event on pregnancy or on the health of the foetus/newborn; animal reproduction studies have not been conducted. Should not be used during pregnancy unless clearly necessary. Not known whether excreted in human milk — caution when prescribing to breast-feeding women.

Betaine

Brand names: Cystadane

Betaine (betaine anhydrous) is a methyl-group donor used in the treatment of homocystinuria to lower elevated plasma homocysteine concentrations.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 100 mg/kg/day (total daily dose)
Route: Oral — powder mixed with water, juice, milk, formula or food until completely dissolved, ingested immediately after mixing
Frequency: Given in 2 doses daily
Source SPC is Amversio 1 g oral powder (betaine anhydrous) for homocystinuria; treatment should be supervised by a physician experienced in treating homocystinuria. The SPC states the same regimen for children and adults. The dose should be individually titrated according to plasma levels of homocysteine and methionine; in some patients doses above 200 mg/kg/day were needed to reach therapeutic goals. Caution with up-titration in patients with CBS deficiency due to the risk of hypermethioninaemia — monitor methionine levels closely and keep plasma methionine below 1,000 micromol/L. Aim of treatment is to keep plasma total homocysteine below 15 micromol/L or as low as possible; steady-state response usually occurs within a month. No dose adaptation needed for renal insufficiency or non-alcoholic hepatic steatosis. Leave 30 minutes between betaine anhydrous and amino acid mixtures and/or medicinal products containing vigabatrin and GABA analogues.

Paediatric dose

Dose: 100 mg/kg
Route: Oral
Frequency: Total daily dose of 100 mg/kg/day given in 2 doses daily
Max: Not stated — in some patients doses above 200 mg/kg/day were needed to reach therapeutic goals
The SPC gives a single regimen for "Children and adults": 100 mg/kg/day in 2 doses daily, individually titrated to plasma homocysteine and methionine levels. Measuring spoons dispense 100 mg, 150 mg or 1 g of betaine anhydrous. Interrupt treatment if symptoms of cerebral oedema (morning headaches with vomiting and/or visual changes) appear.

Dose adjustments

Renal

Experience in patients with renal insufficiency has demonstrated no need to adapt the dose regimen.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Paediatric weight-based calculator

The SPC gives a single regimen for "Children and adults": 100 mg/kg/day in 2 doses daily, individually titrated to plasma homocysteine and methionine levels. Measuring spoons dispense 100 mg, 150 mg or 1 g of betaine anhydrous. Interrupt treatment if symptoms of cerebral oedema (morning headaches with vomiting and/or visual changes) appear.

Verify in a children's formulary

Contraindications

  • Hypersensitivity to the active substance

Side effects

  • Blood methionine increased (very common)
  • Gastrointestinal: diarrhoea, glossitis, nausea, stomach discomfort, vomiting (uncommon)
  • Brain (cerebral) oedema — uncommon, associated with hypermethioninaemia in CBS deficiency; complete recovery after discontinuation
  • Agitation, irritability (uncommon)
  • Hair loss, hives, abnormal skin odour, urinary incontinence, anorexia (uncommon)

Interactions

  • No interaction studies have been performed
  • Amino acid mixtures and medicinal products containing vigabatrin and GABA analogues — possible interaction based on in vitro data; leave 30 minutes between doses

Clinical monograph

How it works

It acts as a substrate for betaine-homocysteine methyltransferase, providing a methyl group that remethylates homocysteine to methionine and so reduces homocysteine levels.

Prescribing in practice

  • Cases of cerebral oedema have been reported, particularly with raised plasma methionine, so monitor and adjust treatment under specialist metabolic supervision.
  • It is used as part of comprehensive management of homocystinuria alongside other measures rather than as monotherapy in isolation.
  • Plasma methionine concentrations can rise during treatment and require monitoring.

Monitoring

Monitor plasma homocysteine and methionine concentrations and watch for symptoms of cerebral oedema under specialist guidance.

Counselling the patient

  • This medicine lowers a harmful amino acid called homocysteine.
  • Attend all blood-test appointments arranged by the metabolic team.
  • Report any severe headache, vomiting or visual changes promptly.

Evidence & guidelines

Betaine is an established treatment for lowering homocysteine in homocystinuria as reflected in specialist metabolic guidance and the SPC.

Reference: BIMDG; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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