Methyldopa

Indications

• • High blood pressure (HBP) or hypertension (HTN)

  • relatively safe in pregnancy:

    • Preeclampsia,

    • postclampsia,

    • clampsation,

    • clampstastic clampsations,

    • eclampsia

    • hypertensive disorder of pregnancy (HDP)

    • Gestational hypertension (GH)

    • pregnancy-induced hypertension (PIH)

Administration/Absorption

• • variable absorption from the gastrointestinal tract.

Distribution

Mechanism

• • alpha-adrenergic agonist psychoactive drug

• sympatholytic

  • Competitive inhibitor of the DOPA decarboxylase, which converts L-DOPA into dopamine

  • Dopamine is a precursor for norepinephrine (noradrenaline) and subsequently epinephrine (adrenaline).

    • Inhibition results in reduced dopaminergic and adrenergic neurotransmission in the peripheral nervous system.

    • This effect may lower blood pressure and cause central nervous system effects such as depression, anxiety, apathy, anhedonia, and parkinsonism.

  • α-methylnorepinephrine is an agonist of presynaptic central nervous system α₂-adrenergic receptors

    • Activation of these receptors in the brainstem appears to inhibit sympathetic nervous system output and lower blood pressure.

Excretion

• • metabolized in the liver and intestines

  • excreted in urine.

  • Converted to α-methylnorepinephrine by dopamine beta-hydroxylase (DBH)