Methyldopa

Indications
 Oral
Hypertension
Adult: Monotherapy: Initially, 250 mg bid-tid for 2 days; adjust according to response not more than every 2 days. Maintenance: 0.5-2 g daily. Max: 3 g daily. Combination therapy: Initial dose should not exceed 500 mg daily in divided doses.
Child: Initially, 10 mg/kg or 300 mg/m2 daily in 2-4 divided doses; increase as necessary. Max: 65 mg/kg, 2 g/m2 or 3 g daily, whichever is least.
Elderly: Initially, 125 mg bid; gradually increase according to response. Max: 2 g daily.
Renal impairment: May respond to smaller doses.
Intravenous
Hypertension
Adult: As methyldopate hydrochloride: 250-500 mg in 100 ml of 5% glucose injected over 30-60 min every 6 hr. Max: 1 g every 6 hr.
Child: As methyldopate hydrochloride: 20-40 mg/kg/24 hr or 0.6-1.2 g/m2/24 hr in equally divided doses every 6 hr. Max 65 mg/kg, 2 g/m2 or 3 g daily, whichever is least.
Renal impairment: May respond to smaller doses.

Incompatibility: Incompatible with amphotericin B, methohexital.
Contraindications
 Phaeochromocytoma, active liver disease. Patients in whom previous methyldopa treatment resulted in liver abnormalities or direct Coombs' positive haemolytic anaemia.
Warnings / Precautions
 History of haemolytic anaemia, depression, parkinsonism, renal or hepatic impairment. May impair ability to drive or operate machinery. Monitor blood counts and perform LFTs. Elderly.
Adverse Reactions
 Peripheral oedema; drug fever, mental depression, anxiety, nightmares, drowsiness, headache; dry mouth; orthostatic hypotension, sinus bradycardia, sodium retention, sexual dysfunction, gynaecomastia, hyperprolactinaemia, thrombocytopenia, positive Coombs' test, transient leukopenia or granulocytopenia, cholestasis or hepatitis and heptocellular injury, increased liver enzymes, jaundice, cirrhosis, dyspnoea, SLE-like syndrome.
Potentially Fatal: Hepatic necrosis, haemolytic anaemia.
Overdose Reactions
 Symptoms: Hypotension, sedation, bradycardia, dizziness, constipation or diarrhoea, flatus, nausea, vomiting. Management: Supportive and symptomatic. Can be removed by hemodialysis.
Drug Interactions
 Reduced hypotensive effects with phenothiazines, TCAs and possibly, amphetamines. Additive hypotensive effects with levodopa; psychosis may also occur. Reduced absorption and effects with oral iron preparations. Reduced doses of general anaesthetics may be required. Effect of ephedrine may be reduced.
Potentially Fatal: Increased risk of severe hypertension with MAOIs. Increased lithium toxicity.
See Below for More methyldopa Drug Interactions
Lab Interactions
 Positive Coombs' test. May interfere with serum creatinine measurement by the alkaline picrate method and with AST estimation by colourimetric methods. May result in falsely high value for urinary catecholamines.
Food Interactions
 Hypertension may be exacerbated with ephedra, yohimbe and ginseng. CNS depression may be increased when used with valerian, St John's wort, kava kava and gotu kola. Natural licorice causes sodium and water retention and increases potassium loss. Garlic may increase antihypertensive effect.
Mechanism of Actions
 Methyldopa stimulates α2-adrenoceptors which results in reduced sympathetic tone and fall in BP.
Onset: 4-6 hr.
Duration: 48 hr (oral); 10-16 hr (IV).
Absorption: Variable and incomplete from the GI tract, via amino acid active transport system (oral).
Distribution: Crosses the placenta; penetrates the blood-brain barrier; enters the breast milk. Protein-binding: Minimal.
Metabolism: Extensively hepatic. CNS: Decarboxylation to α-methyl-noradrenaline.
Excretion: Via urine (as unchanged drug and as o-sulfate conjugate); prolonged in renal impairment; 1.7 hr (elimination half-life).
Administration
 May be taken with or without food.
ATC Classification
 C02AB - Methyldopa ; Used in the treatment of hypertension.
Available As
  • Methyldopa 100 mg
  • Methyldopa 250 mg

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