methyldopa: clinical use

Prescribing considerations

• Assess renal function because renal elimination is important and sensitivity may increase with impairment.
• Older people may be more susceptible to syncope and hypotension.
• Review mood history and monitor for depressive symptoms, particularly around childbirth.
• Inform anaesthetic teams; anaesthetic requirements may be reduced.
• Dialysis removes methyldopa, potentially allowing hypertension to recur.
• Methyldopa can interfere with several biochemical tests and urinary catecholamine measurements.

Contraindications and cautions

• Hypersensitivity to methyldopa or an excipient, including hepatic injury associated with previous methyldopa therapy
• History of depression
• Active hepatic disease, including acute hepatitis or active cirrhosis
• Concurrent monoamine oxidase inhibitor treatment
• Porphyria
• Not suitable for hypertension caused by phaeochromocytoma or paraganglioma

Monitoring

• Monitor blood-pressure response and symptoms of postural hypotension or bradycardia.
• Check liver function and full blood count before treatment and during early therapy, and investigate unexplained fever or jaundice promptly.
• Investigate suspected anaemia for haemolysis; stop treatment if methyldopa-related haemolytic anaemia is confirmed.
• Record a positive direct Coombs test where transfusion or cross-matching is planned.
• Monitor fluid retention, heart-failure features, involuntary movements and mood changes.

Clinical pharmacology

Methyldopa is incompletely absorbed and metabolised to alpha-methylnoradrenaline, which produces predominantly central antihypertensive effects. Elimination is substantially renal, and it crosses the placenta and enters breast milk.

Formulation and product differences

• The selected product is a round, yellow, film-coated biconvex tablet.
• It contains lactose and should remain in its original packaging to protect it from light.

Tablet

Route: Oral

Strengths: 125 mg, 250 mg, 500 mg