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Methyldopa chemical structure
Methyldopa

(2S)-2-amino-3-(3,4-dihydroxyphenyl)-2-methyl-propanoic acid
IUPAC name
CAS number
555-30-6
ATC code

C02AB01

PubChem
4138
DrugBank
APRD01106
Chemical formula {{{chemical_formula}}}
Molecular weight 211.215 g/mol
Bioavailability approximately 50%
Metabolism Hepatic
Elimination half-life 105 minutes
Excretion Renal for metabolites
Pregnancy category a drug of choice in PIH
Legal status Rx-only
Routes of administration Oral, IV

Methyldopa or alpha-methyldopa (brand names Aldomet, Apo-Methyldopa, Dopamet, Novomedopa) is a centrally-acting adrenergic antihypertensive medication. Its use is now deprecated following introduction of alternative safer classes of agents. However it continues to have a role in otherwise difficult to treat hypertension and pregnancy-induced hypertension.

Pharmacokinetics[edit | edit source]

Methyldopa has variable absorption from the gut of approximately 50%. It is metabolized in the intestines and liver; its metabolite alpha-methylnorepineprine acts in the brain to stimulate alpha-adrenergic receptors decreasing total peripheral resistance. It is excreted in urine.

Mechanism of action[edit | edit source]

Methyldopa, in its active metabolite form, is a central alpha-2 receptor agonist. Using methyldopa leads to alpha-2 receptor-negative feedback to sympathetic nervous system (SNS) (centrally and peripherally), allowing peripheral sympathetic nervous system (PSNS) tone to decrease. Such activity leads to a decrease in total peripheral resistance (TPR) and cardiac output.

Rebound effect[edit | edit source]

Rebound hypertension has been reported in some cases when methyldopa has been abruptly withdrawn after extended use[1]. This results because the long term use of methyldopa lowers the sensitivity of presynaptic alpha 2 receptors: the release of norepinephrine (NE) from sympathetic nerve endings is modulated by NE itself acting on the presynaptic alpha 2 autoreceptors thus inhibiting its own release. The discontinuation of methyldopa removes the inhibition on NE release leading to excessive NE release from the SNS and the rebound hypertension.

History[edit | edit source]

When introduced it was a mainstay of antihypertensive therapy, but its use has declined, with increased use of other safer classes of agents. One of its important present-day uses is in the management of pregnancy-induced hypertension, as it is relatively safe in pregnancy compared to other antihypertensive drugs.

Side effects[edit | edit source]

There are many possible reported side-effects with some, whilst rare, being serious. Side effects are usually fewer if the dose is less than 1 g per day:[2]

See also[edit | edit source]

Footnotes[edit | edit source]

Template:Adrenergic agonists Template:Antihypertensives and diuretics Categor:Drugs with psychosis as a side effect

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