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Pronunciation:

(meth il DOE pa)

Synonyms:

Aldomet; Methyldopate Hydrochloride

Generic Available:

Yes

Canadian Brand Names:

Apo-Methyldopa®; Nu-Medopa

Use:

Management of moderate to severe hypertension

Pregnancy Risk Factor:

Pregnancy Implications:

Crosses the placenta. Hypotension reported. A large amount of clinical experience with the use of these drugs for the management of hypertension during pregnancy is available. Available evidence suggests safe use during pregnancy.

Lactation:

Enters breast milk/compatible

Contraindications:

Hypersensitivity to methyldopa or any component of the formulation; active hepatic disease; liver disorders previously associated with use of methyldopa; on MAO inhibitors; bisulfite allergy if using oral suspension or injectable

Warnings/Precautions:

May rarely produce hemolytic anemia and liver disorders; positive Coombs' test occurs in 10% to 20% of patients (perform periodic CBCs); sedation usually transient may occur during initial therapy or whenever the dose is increased. Use with caution in patients with previous liver disease or dysfunction, the active metabolites of methyldopa accumulate in uremia. Patients with impaired renal function may respond to smaller doses. Elderly patients may experience syncope (avoid by giving smaller doses). Tolerance may occur usually between the second and third month of therapy. Adding a diuretic or increasing the dosage of methyldopa frequently restores blood pressure control. Because of its CNS effects, methyldopa is not considered a drug of first choice in the elderly. Often considered the drug of choice for treatment of hypertension in pregnancy. Do not use injectable if bisulfite allergy.

Adverse Reactions:

>10%: Cardiovascular: Peripheral edema

1% to 10%:

Central nervous system: Drug fever, mental depression, anxiety, nightmares, drowsiness, headache

Gastrointestinal: Dry mouth

<1% (Limited to important or life-threatening): Orthostatic hypotension, bradycardia (sinus), sodium retention, sexual dysfunction, gynecomastia, hyperprolactinemia, thrombocytopenia, hemolytic anemia, positive Coombs' test, leukopenia, transient leukopenia or granulocytopenia, cholestasis or hepatitis and heptocellular injury, increased liver enzymes, jaundice, cirrhosis, dyspnea, SLE-like syndrome

Overdosage/Toxicology:

Symptoms of overdose include hypotension, sedation, bradycardia, dizziness, constipation or diarrhea, flatus, nausea, and vomiting. Treatment is supportive and symptomatic. Can be removed by hemodialysis.

Drug Interactions:

Barbiturates and TCAs may reduce response to methyldopa.

Beta-blockers, MAO inhibitors, phenothiazines, and sympathomimetics: Hypertension, sometimes severe, may occur.

Iron supplements can interact and cause a significant increase in blood pressure.

Lithium: Methyldopa may increase lithium toxicity; monitor lithium levels.

Tolbutamide, haloperidol, anesthetics, and levodopa effects/toxicity are increased with methyldopa.

Ethanol/Nutrition/Herb Interactions:

Herb/Nutraceutical: Avoid dong quai if using for hypertension (has estrogenic activity). Avoid ephedra, yohimbe, ginseng (may worsen hypertension). Avoid valerian, St John's wort, kava kava, gotu kola (may increase CNS depression). Avoid natural licorice (causes sodium and water retention and increases potassium loss). Avoid garlic (may have increased antihypertensive effect).

Stability:

Injectable dosage form is most stable at acid to neutral pH; stability of parenteral admixture at room temperature (25°C): 24 hours; stability of parenteral admixture at refrigeration temperature (4°C): 4 days; standard diluent: 250-500 mg/100 mL D5W

Compatibility:

Stable in dextran 6% in NS, D5NS, D5W, sodium bicarbonate 5%, NS

Y-site administration: Compatible: Esmolol, heparin, meperidine, morphine, theophylline. Variable (consult detailed reference): TPN

Compatibility when admixed: Compatible: Aminophylline, ascorbic acid injection, chloramphenicol, diphenhydramine, heparin, magnesium sulfate, multivitamins, potassium chloride, promazine, sodium bicarbonate, succinylcholine, verapamil, vitamin B complex with C. Incompatible: Amphotericin B, methohexital

Mechanism of Action:

Stimulation of central alpha-adrenergic receptors by a false transmitter that results in a decreased sympathetic outflow to the heart, kidneys, and peripheral vasculature

Pharmacodynamics/Kinetics:

Onset of action: Peak effect: Hypotensive: Oral/parenteral: 3-6 hours

Duration: 12-24 hours

Distribution: Crosses placenta; enters breast milk

Protein binding: <15%

Metabolism: Intestinal and hepatic

Half-life elimination: 75-80 minutes; End-stage renal disease: 6-16 hours

Excretion: Urine (85% as metabolites) within 24 hours

Dosage:

Children:

Oral: Initial: 10 mg/kg/day in 2-4 divided doses; increase every 2 days as needed to maximum dose of 65 mg/kg/day; do not exceed 3 g/day.

I.V.: 5-10 mg/kg/dose every 6-8 hours up to a total dose of 65 mg/kg/24 hours or 3 g/24 hours

Adults:

Oral: Initial: 250 mg 2-3 times/day; increase every 2 days as needed (maximum dose: 3 g/day): usual dose range (JNC 7): 250-1000 mg/day in 2 divided doses

I.V.: 250-500 mg every 6-8 hours; maximum dose: 1 g every 6 hours

Dosing interval in renal impairment:

Clcr >50 mL/minute: Administer every 8 hours.

Clcr 10-50 mL/minute: Administer every 8-12 hours.

Clcr<10 mL/minute: Administer every 12-24 hours.

Hemodialysis: Slightly dialyzable (5% to 20%)

Administration:

When methyldopa is administered with antihypertensives other than thiazides, limit initial doses to 500 mg/day

Monitoring Parameters:

Blood pressure, standing and sitting/lying down, CBC, liver enzymes, Coombs' test (direct); blood pressure monitor required during I.V. administration

Test Interactions:

Methyldopa interferes with the following laboratory tests: urinary uric acid, serum creatinine (alkaline picrate method), AST (colorimetric method), and urinary catecholamines (falsely high levels)

Dietary Considerations:

Dietary requirements for vitamin B12 and folate may be increased with high doses of methyldopa.

Patient Education:

Inform prescriber of all prescriptions, OTC medications, or herbal products you are taking, and any allergies you have. Do not take any new medication during therapy unless approved by prescriber (especially any cough or cold remedies, diet pills, stay-awake medications). Oral: Take as directed. Do not skip dose or discontinue without consulting prescriber. Follow recommended diet and exercise program. This medication may cause altered color of urine (normal); drowsiness, dizziness, or impaired judgment (use caution when driving or engaging in tasks that require alertness until response to drug is known); postural hypotension (use caution when rising from sitting or lying position or when climbing stairs); or dry mouth or nausea (frequent mouth care or sucking lozenges may help). Report altered CNS status (eg, nightmares, depression, anxiety, increased nervousness); sudden weight gain (weigh yourself in the same clothes at the same time of day once a week); unusual or persistent swelling of ankles, feet, or extremities; palpitations or rapid heartbeat; persistent weakness, fatigue, or unusual bleeding; or other persistent side effects.

Nursing Implications:

Transient sedation or depression may be common for first 72 hours of therapy; usually disappears over time; infuse over 30 minutes; assist with ambulation

Anesthesia and Critical Care Concerns/Other Considerations:

Most effective if used with diuretic. Titrate dose to optimal blood pressure control with minimal side effects. Patients on methyldopa may need less anesthetic agents. Hypotension readily responds to vasopressors because the adrenergic receptors remain sensitive.

It is used in the management of pregnancy-associated hypertension. Although the drug crosses the placenta and may cause hypotension, there is a large body of experience using this drug in the treatment of pregnancy-associated hypertension. Overall, the medication appears to be safe during pregnancy and lactation.

Cardiovascular Considerations:

Methyldopa is not routinely used for the treatment of essential hypertension. However, it is still used in the management of pregnancy-associated hypertension. Although the drug crosses the placenta and may cause hypotension, there is a large body of experience using this drug in the treatment of pregnancy-associated hypertension. Overall, the medication appears to be safe during pregnancy and lactation. Important side effects to note are hemolytic anemia, drowsiness, and depression.

Dental Health: Effects on Dental Treatment:

Key adverse event(s) related to dental treatment: Xerostomia (normal salivary flow resumes upon discontinuation). Anticholinergic side effects can cause a reduction of saliva production or secretion, contributing to discomfort and dental disease (ie, caries, oral candidiasis, and periodontal disease).

Dental Health: Vasoconstrictor/Local Anesthetic Precautions:

No information available to require special precautions

Mental Health: Effects on Mental Status:

May cause drowsiness, dizziness, anxiety, nightmares, or depression

Mental Health: Effects on Psychiatric Treatment:

Contraindicated with MAO inhibitors; may rarely cause leukopenia; use caution with clozapine and carbamazepine; associated with lithium toxicity; use alternative antihypertensive agent; methyldopa may interact with psychotropics; monitor blood pressure and clinical status

Dosage Forms:

Injection, solution, as methyldopate hydrochloride: 50 mg/mL (5 mL) [contains sodium bisulfite]

Tablet: 250 mg, 500 mg

International Brand Names:

Aldomet® (AR, AU, BE, BR, CH, CZ, DK, EG, ES, FR, GB, HK, IE, IT, LU, MX, NL, NO, NZ, PT, RO, SE, TH, ZA); Aldometil® (AT); Aldomet® [inj.] (GB); Aldomin® (IL); Alfamet® (TR); Alphadopa® (IN); Apo-Methyldopa® (CA, SG); Dopagrand® (AR); Dopamed® (TH); Dopamet® (BD, CY, CZ, EG, HK, ID, IE, JO, KW, LB); Dopanol® (PL); Dopasian® (TH); Dopatral® (AR); Dopegyt® (BD, CZ, DE, EG, HK, HU, PL, RO, RU, SG, SY, TH); Farcodopa® (RO); Fidopa® (BD); Hydopa® (AU); Hy-Po-Tone® (ZA); Isomet® (TH); Kindomet® (BR); Medopa® (ID, TH); Medopren® (IT); Mefpa® (TH); Meldopa® (IE); Merck-Methyldopa® (ZA); Methyldopa Alpharma ApS® (SG); Methyldopa® (CY, GB, NZ, PL, RO, YU); Methyldopa Stada® (DE); Metildopa® (BR, CL, YU); Metildopa Fabra® (AR); Metildopa L.CH.® (CL); Metyldopa Dak® (DK); Normopress® (ZA); Nu-Medopa (CA); Presinol® (DE); Prodopa® (NZ); Rolab-Methyldopa® (ZA); Scandopa® (HK); Siamdopa® (TH); Tensodopa® (PE)

References

Chobanian AV, Bakris GL, Black HR, et al, "The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure: The JNC 7 Report,"JAMA, 2003, 289(19):2560-71.

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