Methyldopa
A prodrug central alpha-2 agonist used for high blood pressure, and a standard choice for high blood pressure in pregnancy.
Drug card
- How it works
- Stimulating alpha-2 receptors in the brainstem to cut sympathetic outflow
- Used for
- High blood pressure in pregnancy
- High blood pressure
- Known for
- Drowsiness, mainly early on or after a dose rise
- Positive Coombs test and hemolytic anemia
- Liver injury: hepatitis and jaundice
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does methyldopa work?
A prodrug: in the brain it becomes alpha-methylnorepinephrine, which stimulates central alpha-2 receptors. Acting as a false transmitter and lowering renin may add to the effect, and the exact mechanism is unproven. It also inhibits dopa decarboxylase and depletes tissue amines. Cardiac output and kidney blood flow are usually preserved.
Like other central alpha-2 agonists: They stimulate alpha-2 adrenergic receptors in the brainstem, which act as a brake on sympathetic nerve traffic. Less norepinephrine is released, so peripheral resistance, heart rate and blood pressure fall. Clonidine acts directly and also binds imidazoline I1 receptors; methyldopa is a prodrug whose metabolite, alpha-methylnorepinephrine, probably acts in the same way.
Uses
What is methyldopa used for?
- High blood pressure in pregnancy
- High blood pressure
Side effects
Side effects of methyldopa
- Drowsiness, mainly early on or after a dose riseKnown for
- Positive Coombs test and hemolytic anemiaKnown forSerious
- Liver injury: hepatitis and jaundiceKnown forSerious
- Dizziness on standing
- Depression and nightmares
- Raised prolactin: breast swelling and milk
- Erectile dysfunction and low libido
- Edema and weight gain
- Parkinsonism and involuntary movements
- Low white cell or platelet countsSerious
- Lupus-like syndromeSerious
- PancreatitisSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Check blood count, Coombs test and liver tests before starting and periodically; stop it for unexplained fever or jaundice.
- Avoid in active liver disease, depression or pheochromocytoma, and with MAOIs.
- A positive Coombs test can complicate cross-matching blood for a transfusion.
- Iron salts (ferrous sulfate or gluconate) reduce its absorption; anyone also taking lithium needs watching for lithium toxicity.
Good to know: Its long record in pregnancy, with no clear harm found in follow-up of children whose mothers took it, keeps it a standard choice for high blood pressure in pregnancy.
Remember it
A way to remember it
Methyldopa for mothers; watch the two Hs: hemolysis and hepatitis.
It is a standard choice for high blood pressure in pregnancy. Its classic dangers are Coombs-positive hemolytic anemia and liver injury, so blood counts, a Coombs test and liver tests are checked before and during treatment.
Written for biofideX
Its class
Central alpha-2 agonists
Other central alpha-2 agonists with a card:
Easily mixed up with alpha-1 blockers, noradrenergic and specific serotonergic antidepressants and beta blockers.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Methyldopa tablets: label (DailyMed)
- Methyldopa 250 mg tablets: SmPC (emc)
- Methyldopa (NCI Thesaurus)
- WHO recommendations on drug treatment for non-severe hypertension in pregnancy (WHO)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Blood pressure
Methyldopa is one of 27 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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