MedeliX
Start asking

Pyrimethamine

ATC code P01BD01

Also known as: Pyrimethamin, Pirimetamin

Key facts
Active substance
Pyrimethamine
Drug class
Antimalarial
ATC code
P01BD01
Authorisation
authorised nationally; no central EU authorisation
Information as of
2026-10-29

Key facts

Pyrimethamine is a folic acid antagonist antiparasitic. Per the US prescribing information, it is used together with a sulfonamide to treat toxoplasmosis.

What it is used for

  • Toxoplasmosis, in combination with a sulfonamide (synergistic effect)

Dosing

  • Adults: initially 50 to 75 mg daily with 1 to 4 g daily of a sulfapyrimidine-type sulfonamide, usually for 1 to 3 weeks; then about half the dose of each drug for another 4 to 5 weeks
  • Children: 1 mg/kg/day in 2 equal doses; after 2 to 4 days reduced to half and continued for about 1 month, with the usual pediatric sulfonamide dose
  • Folinic acid (leucovorin) is strongly recommended for all patients
  • A small starting dose is recommended in convulsive disorders; caution in impaired renal or hepatic function
  • High doses: blood counts including platelets twice a week

Contraindications

  • Known hypersensitivity to pyrimethamine or any component
  • Documented megaloblastic anemia due to folate deficiency

Important warnings

  • Narrow therapeutic window; if folate deficiency develops, reduce the dose or stop and give leucovorin 5 to 15 mg daily until blood formation recovers
  • Possible carcinogenicity (leukemia and sarcoma have been reported in 2 patients)
  • Keep out of reach of children – deaths after accidental ingestion have been reported
  • Stop at the first sign of a skin rash
  • Caution in possible folate deficiency (malabsorption, alcoholism, pregnancy, phenytoin)

Side effects

  • Anorexia and vomiting (fewer when taken with meals)
  • Megaloblastic anemia, leukopenia, thrombocytopenia, pancytopenia, atrophic glossitis, hematuria, heart rhythm disorders
  • Hypersensitivity reactions, occasionally severe (Stevens-Johnson syndrome, toxic epidermal necrolysis, anaphylaxis), particularly with a sulfonamide
  • Rarely pulmonary eosinophilia

Interactions

  • Other antifolates or myelosuppressive drugs (trimethoprim-sulfamethoxazole, proguanil, zidovudine, methotrexate and other cytostatics): increased risk of bone marrow suppression
  • Lorazepam: mild hepatotoxicity reported

Pregnancy and breastfeeding

  • Teratogenic in rats; use only if the benefit justifies the risk, with folinic acid
  • Excreted in breast milk

Summary of the official product information, written with AI on 2026-10-29. Every number was checked automatically against the original text. Not reviewed by a physician – the full official text is authoritative.

Full official text →

Common questions – ask Medelix

For patients

Patient information (US)

This product has no separate US patient information.

Authorisation and brand names by country

Medicines with exactly this active-substance composition, as listed in the national registers – alphabetical and without ranking. Whether a product is currently available is not shown here.

Germany

  • DaraprimGlaxosmithkline Gmbh & Co. Kg · 1 register entry

Source: EMA – Article 57 product data (EU/EEA), as of 2026-10-29

USA

  • DaraprimVyera Pharmaceuticals LLC, TILDE Sciences LLC · 2 register entries

Source: U.S. FDA – Drug labels (openFDA/DailyMed), as of 2026-10-29

Brand names in 6 more European countries
Belgium
Daraprim
France
Malocide
Luxembourg
Daraprim
Netherlands
Daraprim
Portugal
Pirimetamina Labesfal
Spain
Daraprim

EMA – Article 57 product data (EU/EEA), 2026-10-29

Medelix receives no money from pharmaceutical companies. Brand names are listed alphabetically and without ranking.

Another question about this substance?

Medelix answers clinical questions from guidelines, studies and product information – every claim with its source.

Sources

  1. U.S. Food and Drug Administration. Pyrimethamine (OAKRUM PHARMA, LLC) – Prescribing Information, 2021-11-11. DailyMed (NLM), 2026-10-29. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=8ed8141b-e6c0-4a6b-8a08-2858c8c8bd4a
  2. EMA – Article 57 product data (EU/EEA), 2026-10-29. https://www.ema.europa.eu/en/human-regulatory-overview/post-authorisation/data-medicines-iso-idmp-standards-post-authorisation/public-data-article-57-database
  3. U.S. FDA – Drug labels (openFDA/DailyMed), 2026-10-29. https://dailymed.nlm.nih.gov/dailymed/
  4. Wikidata (CC0): ATC P01BD.

Editorial: Medelix editorial team · last updated 2026-10-29 · How these pages are made · Report an error

Source: U.S. Food and Drug Administration (FDA), prescribing information, via DailyMed (NLM); public domain. Not advertising, not a treatment recommendation. For questions about your own treatment, ask your doctor or pharmacist.