Adult: As methyldopate HCl: 250-500 mg 6 hrly over 30-60 min as required. Max: 1,000 mg 6 hrly. Child: 20-40 mg/kg or 600-1,200 mg/m2 daily in equally divided doses 6 hrly. Max: 65 mg/kg, 2,000 mg/m2 or 3,000 mg daily, whichever is least.
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. 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. Elderly: Initially, 125 mg bid; gradually increase according to response. Max: 2,000 mg daily.
May respond to smaller doses.
May be taken with or without food.
Add the required dose to 100 mL of dextrose 5% inj. Alternatively, the required dose may be administered in dextrose 5% inj in a concentration of 100 mg/10 mL.
Active liver disease (e.g. acute hepatitis, active cirrhosis) or depression. Concomitant use w/ MAOIs.
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.
Monitor BP, blood counts, liver enzymes; direct Coombs' test.
Symptoms: Acute hypotension, brain and GI malfunction (e.g. excessive sedation, weakness, bradycardia, dizziness, light-headedness, constipation, distension, flatus, diarrhoea, nausea, vomiting). Management: Symptomatic treatment. Induce emesis or perform gastric lavage if ingestion is recent. Infusions may help promote urinary excretion. May admin sympathomimetic agents.
Potentiation of hypotensive effects w/ diuretics and other antihypertensives. Reduced metabolism w/ COMT inhibitors (e.g. entacapone). Sympathomimetics may antagonise the hypotensive effects of methyldopa. Paradoxical antagonism of hypotensive effects w/ TCAs, antipsychotics and β-blockers. May increase lithium toxicity. Potentially Fatal: Diminished hypotensive effect w/ MAOIs.
Positive Coombs' test. May interfere w/ the measurement of urinary uric acid by the phosphotungstate method, serum creatinine by the alkaline picrate method, and AST (SGOT) by colorimetric method. May interfere w/ the diagnosis of phaeochromocytoma.
Description: Methyldopa stimulates central α-adrenergic receptors by a false neurotransmitter (α-methylnorepinephrine) which results in reduced sympathetic tone and fall in BP. Onset: 4-6 hr. Duration: 12-24 hr (single oral dose); 24-48 hr (multiple oral dose); 10-16 hr (IV). Pharmacokinetics: Absorption: Variably and incompletely absorbed from the GI tract. Bioavailability: Approx 50%. Time to peak plasma concentration: 2-4 hr (oral). Distribution: Crosses the blood-brain barrier and placenta; enters breast milk (small amounts). Volume of distribution: 0.23 L/kg. Plasma protein binding: Minimal (10-15%). Metabolism: Extensively metabolised; converted to active α-methylnorepinephrine via decarboxylation in the CNS. Excretion: Via urine, mainly as unchanged drug and the O-sulfate conjugate. Biphasic elimination half-life: Approx 1.7 hr (initial phase); more prolonged (2nd phase).
C02AB - Methyldopa ; Used in the treatment of hypertension.
Anon. Methyldopa. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 12/10/2015.Buckingham R (ed). Methyldopa. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com/. Accessed 09/10/2015.McEvoy GK, Snow EK, Miller J et al (eds). Methyldopa, Methyldopate Hydrochloride. AHFS Drug Information (AHFS DI) [online]. American Society of Health-System Pharmacists (ASHP). https://www.medicinescomplete.com. Accessed 09/10/2015.Methyldopate Hydrochloride Injection, Solution (American Regent, Inc.). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 12/10/2015.