methyldopa (redirected from Dopamet)

methyldopa /meth·yl·do·pa/ (-do´pah) a phenylalanine derivative used in the treatment of hypertension.

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meth·yl·do·pa (mthl-dp)

n.

A drug used in the treatment of high blood pressure.

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methyldopa

[-dō′pə]

an alpha₂ receptor agonist that acts in the central nervous system to decrease sympathetic nervous system outflow.

indications It is prescribed for the reduction of hypertension in moderate to severe cases.

contraindications Use of monoamine oxidase inhibitors, liver dysfunction, or known hypersensitivity to this drug prohibits its use.

adverse effects Among the more serious adverse effects are liver toxicity and blood dyscrasias. Sedation, dry mouth, nasal stuffiness, and postural hypotension may occur.

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methyldopa

Aldomet (UK), Apo-Methyldopa (CA), Dopamet (CA), Novomedopa (CA), Nu-Medopa (CA)

Pharmacologic class: Centrally acting antiadrenergic

Therapeutic class: Antihypertensive

Pregnancy risk category B

Action

Stimulates CNS alpha-adrenergic receptors, decreasing sympathetic stimulation to heart and blood vessels. Also reduces arterial pressure and plasma renin.

Availability

Injection: 50 mg/ml in 5- and 10-ml vials

Oral suspension (contains bisulfites): 250 mg/5 ml

Tablets: 125 mg, 250 mg, 500 mg

⊘Indications and dosages

➣ Hypertension

Adults: 250 mg P.O. two to three times daily for 2 days (not to exceed 500 mg/day in divided doses if used with other agents); may increase q 2 days as needed. Usual maintenance dosage is 500 mg to 2 g/day (not to exceed 3 g/day) P.O. in two to four divided doses or 250 to 500 mg I.V. q 6 hours (up to 1 g q 6 hours).

Children: 10 mg/kg/day (300 mg/m²/day) P.O. in two to four divided doses. May increase q 2 days up to 65 mg/kg/day (2 g/m²/day), or 3 g/day in divided doses (whichever is lower) or 5 to 10 mg/kg I.V. q 6 hours; up to 65 mg/kg/day (2 g/m²/day), or 3 g/day in divided doses (whichever is lower).

Contraindications

• Hypersensitivity to drug or its components
• Pheochromocytoma
• Active hepatic disease or history of methyldopa-associated hepatic disorders
• MAO inhibitor use within past 14 days

Precautions

Use cautiously in:
• heart failure, edema, hemolytic anemia, hypotension, severe bilateral cerebrovascular disease
• dialysis patients
• elderly patients
• pregnant or breastfeeding patients.

Administration

☞ Don't give within 14 days of MAO inhibitors.
• To prepare I.V. infusion, add prescribed dosage to 100 ml 5% dextrose injection. Or administer in 5% dextrose injection in a concentration of 100 mg/10 ml. Give each dose over 30 to 60 minutes.
• Dilute and administer ADD-Vantage vials containing 50 mg/ml according to manufacturer's instructions.
☞ Don't stop drug therapy abruptly.

Route	Onset	Peak	Duration
P.O.	Unknown	4-6 hr	24-48 hr
I.V.	Unknown	4-6 hr	10-16 hr

Adverse reactions

CNS: headache, asthenia, weakness, dizziness, sedation, decreased mental acuity, depression, paresthesia, parkinsonism, Bell's palsy, involuntary choreoathetotic movements

CV: bradycardia, edema, orthostatic hypotension, myocarditis

EENT: nasal congestion

GI: nausea, vomiting, diarrhea, constipation, abdominal distention, colitis, dry mouth, sialadenitis, sore or black tongue, pancreatitis GU: breast enlargement, gynecomastia, failure to ejaculate, erectile dysfunction

Hematologic: eosinophilia, hemolytic anemia

Hepatic: hepatitis

Other: fever

Interactions

Drug-drug. Adrenergics, MAO inhibitors: excessive sympathetic stimulation

Amphetamines, barbiturates, nonsteroidal anti-inflammatory drugs, phenothiazines, tricyclic antidepressants: decreased antihypertensive effect

Anesthestics, antihypertensives, nitrates: additive hypotension

Ferrous gluconate, ferrous sulfate: decreased methyldopa blood level

Haloperidol: increased haloperidol effects, increased risk of psychoses

Levodopa: additive hypotension and CNS toxicity

Lithium: increased risk of lithium toxicity

Nonselective beta-adrenergic blockers: paradoxical hypertension

Tolbutamide: increased tolbutamide effects

Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, bilirubin, blood urea nitrogen, creatinine, potassium, prolactin, sodium, uric acid: increased levels

Direct Coombs' test: positive result

Liver function tests: abnormal results

Prothrombin time: prolonged

Drug-herbs. Capsicum: reduced antihypertensive effects

Drug-behaviors . Alcohol use: increased hypotension

Patient monitoring

• Obtain direct Coombs' test before therapy starts and 6 and 12 months later.
• Monitor periodic blood counts to detect adverse hematologic reactions.
• Monitor liver function tests and check for signs and symptoms of hepatic dysfunction (particularly during first 6 to 12 weeks of therapy).
• Check for edema or weight gain to help determine if diuretic should be added to regimen.
• Monitor blood pressure. Drug tolerance may occur during second and third months of therapy.

Patient teaching

• Tell patient that sedation usually occurs when therapy starts and during dosage titration. To lessen this effect, advise him to begin dosage titration in evening.
☞ Tell patient not to stop taking drug abruptly.
☞ Instruct patient to report fever, yellowing of skin or eyes, fatigue, abdominal pain, flulike symptoms, swelling, or significant weight gain.
• Inform patient that urine may darken after exposure to air.
• Advise patient to move slowly when changing position, to avoid dizziness from sudden blood pressure decrease.
• Caution patient to avoid driving and other hazardous activities until effects of drug are known or dosage titration is completed.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.