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methyldopa (Aldomet)

Tradename: Aldomet. Indications: 1) management of moderate to severe hypertension 2) 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. Injection: 50 mg/mL (5 mL) Pharmacokinetics: 1) oral bioavailability is 42% 2) IV bioavailability similar to oral 3) 10-15% of drug bound to plasma proteins 4) decarboxylated to form alpha-methyl-dopamine & alpha-methyl- norepinephrine in CNS 5) eliminated in the urine 6) 1/2life is 1.8 hours, increased with renal insufficiency 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: 1) common (> 10%) - peripheral edema 2) 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 4) other - weight gain - nasal stuffiness Drug interactions: 1) phenothiazines, tricyclic antidepressants in combination decrease hypotensive effect & may result in psychomotor retardation & memory impairment 2) MAO inhibitors are contraindicated 3) lithium in combination may result in lithium toxicity 4) levodopa in combination may result in additive hypotensive effect & psychosis 5) iron preparations decrease absorption of methyldopa by 60-70% Test interactions: 1) direct Coomb's test may be positive (10-20% @ 6-12 months of therapy) 2) methyldopa may interfere with fluorometric assay for catecholamines Laboratory: 1) specimen: serum, plasma (heparin, EDTA) 2) methods: fluorometry, color, HPLC, MS 3) interferences: -> HPLC: high concentrations of L-dopa may interfere Mechanism of action: 1) central adrenergic agonist 2) decarboxylated to form alpha-methyl-norepinephrine in CNS 3) alpha-methyl-norepinephrine stimulates centrally-acting adrenergic receptors thus lowering blood pressure

Interactions

drug interactions drug adverse effects (more general classes)

Specific

methyldopate (Aldomet ester)

General

centrally-active alpha-adrenergic receptor agonist

Properties

AGONIST-FOR: adrenergic receptor MISC-INFO: elimination route KIDNEY LIVER 1/2life 1.6-2.0 HOURS therapeutic-range 1-5 UG/ML toxic-range >7 UG/ML protein-binding 20% elimination by hemodialysis + peritoneal dialysis + pregnancy-category B safety in lactation ?

Database Correlations

PUBCHEM correlations

References

  1. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  2. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  3. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  4. Clinical Guide to Laboratory Tests, NW Tietz (ed) 3rd ed, WB Saunders, Philadelpha 1995
  5. deprecated reference
  6. Prescriber's Letter 17(7): 2010 Recommended Lab Monitoring for Common Medications Liver Function Test Scheduling Detail-Document#: 260704 (subscription needed) http://www.prescribersletter.com

Component-of

chlorothiazide/methyldopa (Aldoclor) hydrochlorothiazide/methyldopa; HCTZ/methyldopa (Aldoril)