Alpha Methyldopa; Indications/Uses, Dosage, Side effects, Interaction ,Pregnancy

Methyldopa

Methyldopa is a phenylalanine derivative and an aromatic amino acid decarboxylase inhibitor with antihypertensive activity. Methyldopa is an alpha-2 adrenergic agonist that has both central and peripheral nervous system effects. Its primary clinical use is as an antihypertensive agent. Methyldopa is a prodrug and is metabolized in the central nervous system. The antihypertensive action of methyldopa seems to be attributable to its conversion into alpha-methylnorepinephrine, which is a potent alpha-2 adrenergic agonist that binds to and stimulates potent central inhibitory alpha-2 adrenergic receptors. This results in a decrease in sympathetic outflow and decreased blood pressure.

 

Methyldopa is a medication used for high blood pressure. It is one of the preferred treatments for high blood pressure in pregnancy. For other types of high blood pressure including very high blood pressure resulting in symptoms other medications are typically preferred. It can be given by mouth or by injection into a vein. The onset of effects is around 5 hours and them last about a day.

Mechanism of Action of Alpha Methyldopa

Although the mechanism of action has yet to be conclusively demonstrated, the resultant hypotensive effect is most likely due to the drug’s action on the CNS. Methyldopa is converted into the metabolite, alpha-methylnorepinephrine, in the CNS, where it stimulates the central inhibitory alpha-adrenergic receptors, leading to a reduction in sympathetic tone, total peripheral resistance, and blood pressure. Reduction in plasma renin activity, as well as the inhibition of both central and peripheral norepinephrine and serotonin production, may also contribute to the drug’s antihypertensive effect, although this is not a major mechanism of action. This is done through the inhibition of the decarboxylation of dihydroxyphenylalanine (dopa)—the precursor of norepinephrine—and of 5-hydroxytryptophan (5-HTP)—the precursor of serotonin—in the CNS and in most peripheral tissues.

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Indications of Alpha Methyldopa

Contra-Indications of Alpha Methyldopa

The dosage of Alpha Methyldopa

Strengths:  250 mg; 500 mg; 125 mg; 50 mg/mL, 250 mg/5 mL

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.

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.

Side Effects of Alpha Methyldopa

The most common

More common

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Rare

Drug Interactions of Alpha Methyldopa

Alpha-methyldopa may interact with following drug, supplements, & may change the efficacy of the drug

Pregnancy Catagory of Alpha Methyldopa

FDA Pregnancy Category B
Pregnancy

Methyldopa crosses the placenta, and may cause mild hypotension in neonates of treated mothers. Because it has been safely and successfully used to treat hypertension during pregnancy, some experts consider it to be the drug of choice for the treatment of nonemergent hypertension during pregnancy.

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Lactation

Because of the low levels of methyldopa in breastmilk, amounts ingested by the infant are small and would not be expected to cause any adverse effects in breastfed infants. No special precautions are required.

References