Methyldopa

Indications

Methyldopa is used for: Hypertension

Adult Dose

Oral Hypertension Adult: Monotherapy: Initially, 250 mg bid-tid for 2 days; adjust at intervals of at least 2 days according to response. Maintenance: 500-2,000 mg daily. Max: 3,000 mg daily. Combination therapy: Initial dose should not exceed 500 mg daily in divided doses. Elderly: Initially, 125 mg bid; gradually increase according to response. Max: 2,000 mg daily.

Child Dose

Oral Hypertension Child: <12 yr Initially, 10 mg/kg or 300 mg/m2 daily in 2-4 divided doses; adjust at intervals of at least 2 days according to response. Max: 65 mg/kg, 2,000 mg/m2 or 3,000 mg daily, whichever is least.

Renal Dose

Renal Impairment Adjust dosage frequency with renal impairment CrCl >50 mL/min: q8hr CrCl 10-50 mL/min: q8-12hr CrCl <10 mL/min: q12-24hr

Administration

May be taken with or without food.

Contra Indications

Active liver disease (e.g. acute hepatitis, active cirrhosis) or depression. Concomitant use w/ MAOIs.

Precautions

Patient w/ history of haemolytic anaemia, liver disease or depression; parkinsonism, hepatic porphyria. Not intended for the treatment of phaeochromocytoma. Renal or hepatic impairment. Childn, elderly. Pregnancy and lactation. Patient Counselling May impair ability to drive or operate machinery. Monitoring Parameters Monitor BP, blood counts, liver enzymes; direct Coombs' test. Lactation: distributed in breast milk but not in clinically significant amounts; compatible w/ breastfeeding

Pregnancy-Lactation

Pregnancy Category: B Lactation: distributed in breast milk but not in clinically significant amounts; compatible w/ breastfeeding

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

Adverse Effects

Side effects of Methyldopa : Drowsiness, orthostatic hypotension, nausea, headache, weakness, fatigue, decreased libido, impotence, impaired concentration and memory, mild psychoses, depression, disturbed sleep, nightmares, paraesthesias, Bell's palsy, parkinsonism, involuntary choreoathetotic movements, oedema, fluid retention, exacerbation of angina pectoris, bradycardia, syncope, prolonged carotid sinus hypersensitivity, paradoxical HTN, GI disturbances (e.g. nausea, vomiting, diarrhoea, constipation), black/sore tongue, inflamed salivary glands, dry mouth, fever, eosinophilia, liver function disturbances, hepatitis, lupus-like syndrome, rashes, lichenoid and granulomatous eruptions, toxic epidermal necrolysis, flu-like syndrome, nocturia, uraemia, nasal congestion, retroperitoneal fibrosis, hyperprolactinaemia, breast enlargement (including gynaecomastia), galactorrhoea, amenorrhoea. Rarely, pancreatitis and colitis, immune thrombocytopenia, reversible leucopenia (primarily granulocytopenia). Potentially Fatal: Hepatic necrosis, haemolytic anaemia, hypersensitivity myocarditis.

Mechanism of Action

Methyldopa stimulates alpha 2-adrenoceptors which results in reduced sympathetic tone and fall in BP.