【藥品性質提示】 根據 2019 AGS Beers Criteria，本藥品為【潛在不適當用藥 (PIM)】，不建議用於老年人。

高血壓 (其他) Methyldopa is used alone or in combination with other classes of antihypertensive agents in the management of hypertension.

Methyldopa is decarboxylated to form α-methylnorepinephrine in the CNS, where it lowers arterial pressure by stimulation of central inhibitory α-adrenergic receptors. Reduction of plasma renin activity (PRA) may also contribute to the hypotensive effect of methyldopa.

Methyldopa is partially absorbed from the GI tract. The degree of absorption varies among individuals and in the same patient from day to day, but generally about 50% of an oral dose is absorbed. Methyldopa and its metabolites are weakly bound to plasma proteins. Methyldopa is extensively metabolized mainly to the conjugate, methyldopa mono-O-sulfate, probably in the GI tract and the liver. Methyldopa is excreted in urine largely by glomerular filtration, primarily unchanged and as the mono-O-sulfate conjugate. Plasma concentrations of methyldopa decline in a biphasic manner; in patients with normal renal function, 95% of the drug is eliminated during the initial phase with a plasma half-life of 1.8 hours; the second phase is much slower.

Methyldopa is contraindicated in patients receiving monoamine oxidase (MAO) inhibitors and in patients who are hypersensitive to the drug or any ingredient in its formulation.

Methyldopa has been used for many years in the management of hypertension in pregnant women, and the drug is generally considered safe for mother and fetus when used in association with careful prenatal management.

Since methyldopa is distributed into milk, the drug should be used with caution in nursing women; the possibility of adverse effects on a nursing infant cannot be excluded.

Drowsiness, dryness of mouth and headache.

The usual initial adult oral dosage of methyldopa is 250 mg 2 or 3 times daily for 2 days. Dosage may then be increased or decreased at intervals of at least 2 days until an adequate response is achieved. The usual maintenance dosage of methyldopa recommended by the manufacturers is 500 mg to 2 g daily given in 2–4 divided doses; dosages exceeding 3 g daily are not recommended by the manufacturers.