methyldopa (Aldomet)
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Introduction
Tradename: Aldomet.
Indications
- management of moderate to severe hypertension
- in pregnancy-induced hypertension, alpha-methyldopa is considered the drug of choice since it appears to have no apparent adverse effects on the fetus
Contraindications
- concurrent use of MAO inhibitor
Dosage
- Start 250 mg PO BID/TID, max 3 g/day.
- IV loading dose 250 mg, then 250-500 mg every 6 hours.
- Maximum cumulative dose 2 g.
Tabs: 125, 250, 500 mg.
Suspension: 250 mg/5 mL.
Pharmacokinetics
- oral bioavailability is 42%
- IV bioavailability similar to oral
- 10-15% of drug bound to plasma proteins
- decarboxylated to form alpha-methyl-dopamine & alpha-methyl- norepinephrine in CNS
- eliminated in the urine
- 1/2life is 1.8 hours, increased with renal insufficiency
elimination via kidney
elimination via liver
1/2life = 1.6-2.0 hours
protein binding = 20 %
elimination by hemodialysis = +
elimination by peritoneal dialysis = +
Monitor
- serum ALT or serum AST baseline & periodically especially during the 1st 6-11 weeks of therapy, or when unexplained fever occurs[6]
- complete blood cout (CBC) within 180 days[5]
Adverse effects
- common (> 10%)
- less common (1-10%)
- drug fever, depression, anxiety, nightmares, drowsiness, dry mouth, headache C3) uncommon (< 1%)
- colitis, cholestasis, hepatitis, jaundice, pancreatitis, nausea/vomiting, cirrhosis, hepatic necrosis, fever/chills, dyspnea, hemolytic anemia, leukopenia (transient), thrombocytopenia, decreased libido, hyperprolactinemia, gynecomastia, SLE-like syndrome, orthostatic hypotension, sinus bradycardia, sedation, vertigo, depression, paresthesias, weakness, memory disturbance, rash, sodium retention, black tongue
- other
- drug adverse effects of adrenergic receptor agonists
- drug adverse effects of sympathomimetic(s)
- drug adverse effects of antihypertensive agents
Drug interactions
- phenothiazines, tricyclic antidepressants in combination decrease hypotensive effect & may result in psychomotor retardation & memory impairment
- MAO inhibitors are contraindicated
- lithium in combination may result in lithium toxicity
- levodopa in combination may result in additive hypotensive effect & psychosis
- iron preparations decrease absorption of methyldopa by 60-70%
Test interactions
- direct Coomb's test may be positive (10-20% @ 6-12 months of therapy)
- methyldopa may interfere with fluorometric assay for catecholamines
Laboratory
Mechanism of action
- central adrenergic agonist
- decarboxylated to form alpha-methyl-norepinephrine in CNS
- alpha-methyl-norepinephrine stimulates centrally-acting adrenergic receptors thus lowering blood pressure
More general terms
More specific terms
Component of
References
- ↑ The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
- ↑ Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
- ↑ Kaiser Permanente Northern California Regional Drug Formulary, 1998
- ↑ Clinical Guide to Laboratory Tests, NW Tietz (ed) 3rd ed, WB Saunders, Philadelpha 1995
- ↑ 5.0 5.1 deprecated reference
- ↑ 6.0 6.1 Prescriber's Letter 17(7): 2010 Recommended Lab Monitoring for Common Medications Liver Function Test Scheduling Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=260704&pb=PRL (subscription needed) http://www.prescribersletter.com