chemistry

Methyldopa

Methyldopa is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Methyldopa rather than just read about it. In short: 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.

Key takeaways

Methyldopa belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Methyldopa to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Methyldopa from memory before moving on to harder problems.

Reference excerpt

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 injection into a vein. Onset of effects is around 5 hours and they last about a day. Common side effects include sleepiness. More severe side effects include red blood cell breakdown, 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.

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

Hypertension (or high blood pressure) Gestational hypertension (or pregnancy-induced hypertension) and pre-eclampsia.

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. Side effects may include:

Psychological Depression Suicidal ideation Nightmares 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, desire, and drive Physiological Dizziness, lightheadedness, or vertigo Miosis or pupil constriction Xerostomia or dry mouth Gastrointestinal disturbances such as diarrhea or constipation Headache or migraine Myalgia or muscle aches, arthralgia or joint pain, or paresthesia ("pins and needles") Restless legs syndrome (RLS) Parkinsonian symptoms such as muscle tremors, rigidity, hypokinesia, or balance or postural instability Akathisia, ataxia, dyskinesia, as well as even tardive dyskinesia or dystonia Bell's palsy or facial paralysis Sexual dysfunction Hyperprolactinemia Gynecomastia in males, amenorrhoea or absence of menstrual cycles in females Bradycardia Hypotension Orthostatic hypotension Hepatitis, hepatotoxicity, or liver dysfunction or damage 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., skin lesions or rashes) Pallor

Withdrawal Rebound hypertension via withdrawal on account of tolerance upon the abrupt discontinuation of methyldopa has been reported.

Mechanism of action The mechanism of action of methyldopa is not fully clear. It may reduce the dopaminergic and serotonergic 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.

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 metabolized in the liver and intestines and is excreted in urine.

History When methyldopa was first introduced, it was the mainstay of antihypertensive treatment, 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 alpha blockers, beta blockers, 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.

See also Difluoromethyldopa D-DOPA (dextrodopa) L-DOPA (levodopa; trade names Sinemet, Pharmacopa, Atamet, Stalevo, Madopar, Prolopa, etc.) L-DOPS (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

References

External links

Illustrations

Worked examples

Example 1 — a first encounter with Methyldopa

Start with the simplest possible case. Write down what Methyldopa claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Methyldopa before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Methyldopa ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Methyldopa

In research: Methyldopa appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Methyldopa in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Methyldopa is common in secondary-school and first-year university syllabi. It links to neighbouring topics Alpha1-adrenergic agonists, Alpha2-adrenergic agonists, Antihypertensive agents, so understanding it makes those chapters shorter.
In everyday life: Look for Methyldopa outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Methyldopa in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Methyldopa means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Methyldopa out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Methyldopa in simple terms?

Why does Methyldopa matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Methyldopa?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Methyldopa.