Methyldopa

 ( Catecholamines ) 

Methyldopa, also known as α-methyl-L-DOPA and sold under the brand name Aldomet among others, 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 intravenous. Onset of effects is around 5 hours and they last about a day.

Common side effects include sleepiness. More severe side effects include hemolysis, liver problems, and allergic reactions. Methyldopa is in the alpha-2 adrenergic receptor agonist family of medication. It works by stimulating the brain to decrease the activity of the sympathetic nervous system.

Methyldopa was discovered in 1960.

It is on the World Health Organization's List of Essential Medicines.

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Medical uses Methyldopa is used in the clinical treatment of the following medical disorder:

• Hypertension (or high blood pressure)
• Gestational hypertension (or pregnancy-induced hypertension) and pre-eclampsia.
  (2025). 9780323429733, Elsevier. ISBN 9780323429733

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Side effects Methyldopa is capable of inducing a number of adverse side effects, which range from mild to severe. Nevertheless, they are generally mild when the dose is less than 1 gram per day.

(2008). 9780853697787 ISBN 9780853697787

Side effects may include:

• Psychological
• Depression
• Suicidal ideation
• Apathy, anhedonia, or dysphoria
• Anxiety, especially social anxiety
• Decreased alertness, awareness, and wakefulness
• Impaired attention and concentration
• Fatigue
• Malaise
• Drowsiness
• Restlessness
• Cognitive and memory impairment
• Derealization or depersonalization, as well as mild psychosis
• Sexual dysfunction including impaired libido, sexual desire, and sexual drive
• Physiological
• Dizziness, lightheadedness, or vertigo
• Miosis or pupil constriction
• Xerostomia or dry mouth
• Gastroenteritis such as diarrhea or constipation
• Headache or migraine
• Myalgia or , arthralgia or joint pain, or paresthesia ("pins and needles")
• Restless legs syndrome (RLS)
• Parkinsonian such as , muscle rigidity, hypokinesia, or balance disorder
• Akathisia, ataxia, dyskinesia, as well as even tardive dyskinesia or dystonia
• Bell's palsy or facial paralysis
• Sexual dysfunction
• Hyperprolactinemia
• Gynecomastia in , amenorrhoea or absence of in
• Bradycardia
• Hypotension
• Orthostatic hypotension
• Hepatitis, hepatotoxicity, or liver dysfunction or toxicity
• Pancreatitis
• Warm autoimmune hemolytic anemia or deficiency in red blood cells (RBCs)
• Myelotoxicity or bone marrow suppression, potentially leading to thrombocytopenia, blood platelet deficiency, leukopenia, or white blood cell deficiency
• Hypersensitivity (e.g., lupus erythematosus, myocarditis, or pericarditis)
• Lichenoid reactions (e.g., or )
• Pallor

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Withdrawal Rebound effect hypertension via Drug withdrawal on account of drug tolerance upon the abrupt discontinuation of methyldopa has been reported. Methyldopa (PIM 342)

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Mechanism of action The mechanism of action of methyldopa is not fully clear. It may reduce the dopaminergic and Serotonin transmission in the central and peripheral nervous system and it indirectly affects norepinephrine (noradrenaline) synthesis by way of inhibiting dopamine synthesis. Methyldopa acts on alpha-2 adrenergic receptors, which are found on the pre synaptic nerve terminal. This inhibits the release of norepinephrine from the presynaptic neuron.

The S-enantiomer of methyldopa is a competitive inhibitor of the enzyme aromatic L-amino acid decarboxylase (LAAD), which converts L-DOPA into dopamine. L-DOPA can cross the blood–brain barrier and thus methyldopa may have similar effects. LAAD converts it into alpha-methyldopamine, a false precursor to norepinephrine, which in turn reduces synthesis of norepinephrine in the vesicles. Dopamine beta hydroxylase (DBH) converts alpha-methyldopamine into alpha-methylnorepinephrine, which is an agonist of the presynaptic α₂-adrenergic receptor causing inhibition of neurotransmitter release.

Methyldopa has been found to be a monoamine depleting agent.

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Pharmacokinetics

Maximum decrease in blood pressure occurs 4–6 hours after oral dosage. The half-life of methyldopa is 105 minutes. Methyldopa exhibits variable absorption from the gastrointestinal tract. It is metabolism in the liver and and is excretion in urine.

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History

When methyldopa was first introduced, it was the mainstay of antihypertensive therapy, but its use has declined on account of relatively severe adverse side effects, with increased use of other safer and more tolerable agents such as , , and calcium channel blockers. Additionally, it has yet to be associated with reducing adverse cardiovascular events including myocardial infarction and stroke, or overall all-cause mortality reduction in clinical trials. Nonetheless, one of methyldopa's still current indications is in the management of pregnancy-induced hypertension (PIH), as it is relatively safe in pregnancy compared to many other antihypertensives which may affect the fetus.

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See also

• Difluoromethyldopa
• D-DOPA (dextrodopa)
• L-DOPA (levodopa; trade names Sinemet, Pharmacopa, Atamet, Stalevo, Madopar, Prolopa, etc.)
• Droxidopa (droxidopa)
• Dopamine (Intropan, Inovan, Revivan, Rivimine, Dopastat, Dynatra, etc.)
• Norepinephrine (noradrenaline; Levophed, etc.)
• Epinephrine (adrenaline; Adrenalin, EpiPed, Twinject, etc.)
• MK-872 HCl salt: 55943-64-1
• α-Methyltyrosine
• α-Methyl-5-hydroxytryptophan

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External links

Categories: Catecholamines, Aromatic L-amino Acid Decarboxylase Inhibitors, Alpha1-adrenergic Agonists, Alpha2-adrenergic Agonists, Antihypertensive Agents, Beta-adrenergic Agonists, Hepatotoxins, World Health Organization Essential Medicines, Wikipedia Medicine Articles Ready To Translate

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