Drug information of Methyldopa


Drug group:

Methyldopa lowers blood pressure by decreasing the levels of certain chemicals in your blood. This allows your blood vessels (veins and arteries) to relax (widen) and your heart to beat more slowly and easily. Methyldopa is used to treat hypertension (high blood pressure).

Mechanism of effect

Methyldopa is an aromatic-amino acid decarboxylase inhibitor. the antihypertensive effect of Methyldopa probably is due to its metabolism to alpha-methylnorepinephrine, which then lowers arterial pressure by stimulation of central inhibitory alpha-adrenergic receptors, false neurotransmission, and/or reduction of plasma renin activity.


An alpha-2 adrenergic agonist that has both central and peripheral nervous system effects. Its primary clinical use is as an antihypertensive agent.


Absorption from the gastrointestinal tract is variable but averages approximately 50%. The maximum decrease in blood pressure occurs four to six hours after oral dosage. Methyldopa is extensively metabolized. Approximately 70% of the drug which is absorbed is excreted in the urine as Methyldopa and its mono-O-sulfate conjugate Methyldopa crosses the placental barrier, appears in cord blood, and appears in breast milk.


Usual Adult Dose for Hypertension
Initial dose: 250 mg orally 2-3 times a day or 250 to 500 mg IV over 30 to 60 minutes every 6 hours, up to a maximum of 3 g/day.
Maintenance dose: 500 mg to 2 g orally divided in 2 to 4 doses, up to a maximum of 3 g/day.
Usual Adult Dose for Hypertensive Emergency
250 to 500 mg IV over 30 to 60 minutes every 6 hours up to a maximum of 1 g every 6 hours or 4 g/day. Switch to the oral route at the same dosage once blood pressure is under control.


1-It is important to recognize that a positive Coombs test, hemolytic anemia, and liver disorders may occur with Methyldopa therapy.
2- Methyldopa should be used with caution in patients with a history of previous liver disease or dysfunction

Points of recommendation

1-Blood count, Coombs test and liver function tests are recommended before initiating therapy and at periodic intervals
2- Increase dietary intake of magnesium, folate, vitamin B6, B12, and/or consider taking a multivitamin.
3- No iron, zinc or fluoride within 2 hours of taking this medication.
4- Take without regard to meals.

Pregnancy level


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