II. Indications
-
Toxoplasmosis in immunocompetent patients (FDA approved)
- Has been used off label for Toxoplasmosis in HIV and Congenital Toxoplasmosis
- Previously used to treat Malaria
III. Contraindications
-
G6PD Deficiency
- Risk of Hemolytic Anemia
IV. Mechanism
- Synthetic derivative of ethyl Pyrimidine with Antiparasitic and antimalarial activity
- Competitive inhibitor of dihydrofolate reductase (DHFR).
- DHFR is a key enzyme in Tetrahydrofolate synthesis, and in turn DNA and Protein synthesis
V. Medications
- Tablet: 25 mg
- Only available directly from manufacturer
VI. Dosing: Toxoplasmosis in Immunocompetent Patients
- Used in combination with leucovorin and Sulfadiazine
- Combined with leucovorin to prevent hematologic adverse effects
- Combined with Sulfadiazine to broaden coverage
- Dosing is for immunocompetent patients
- See other resources for HIV related ToxoplasmosisEncephalitis
- See other resources for Congenital Toxoplasmosis
- Adult
- Start 50 to 75 mg orally daily for 1 to 3 weeks (use lower dose in Seizure Disorder)
- Next decrease dose 50% daily for an additional 5 weeks
- Child
- Start 1 mg/kg/day orally twice daily for 2 to 4 days
- Next decrease dose 50% for an additional 4 weeks
VII. Adverse Effects
-
Hypersensitivity Reaction
- Most commonly presents as a Cutaneous Drug Eruption (esp. when combined with a Sulfonamide)
- Hematologic Effects
- Thrombocytopenia, Leukopenia, and Anemia may occur
- Hemolytic Anemia with G6PD
- Gastrointestinal
-
Folate Deficiency
- Dose dependent
- Neurologic
VIII. Safety
- Pregnancy Category C
- Considered safe in Lactation
IX. Resources
- Pyrimethamine Tablet (DailyMed)
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Related Studies
Definition (NCI) | A synthetic derivative of ethyl-pyrimidine with potent antimalarial properties. Pyrimethamine is a competitive inhibitor of dihydrofolate reductase (DHFR). DHFR is a key enzyme in the redox cycle for production of tetrahydrofolate, a cofactor that is required for the synthesis of DNA and proteins. This agent is often used in combination with other antimalarials for the treatment of uncomplicated falciparum malaria. (NCI04) |
Definition (MSH) | One of the FOLIC ACID ANTAGONISTS that is used as an antimalarial or with a sulfonamide to treat toxoplasmosis. |
Definition (PDQ) | A synthetic derivative of ethyl-pyrimidine with potent antimalarial properties. Pyrimethamine is a competitive inhibitor of dihydrofolate reductase (DHFR). DHFR is a key enzyme in the redox cycle for production of tetrahydrofolate, a cofactor that is required for the synthesis of DNA and proteins. This agent is often used in combination with other antimalarials for the treatment of uncomplicated falciparum malaria. Check for "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=39578&idtype=1" active clinical trials or "http://www.cancer.gov/Search/ClinicalTrialsLink.aspx?id=39578&idtype=1&closed=1" closed clinical trials using this agent. ("http://nciterms.nci.nih.gov:80/NCIBrowser/ConceptReport.jsp?dictionary=NCI_Thesaurus&code=C788" NCI Thesaurus) |
Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
MSH | D011739 |
SnomedCT | 373769001, 59589008 |
LNC | LP32679-0, MTHU016256 |
English | Pyrimethamine, pyrimethamine, 2,4-Pyrimidinediamine, 5-(4-chlorophenyl)-6-ethyl-, pyrimethamine (medication), PYRIMETHAMINE, Pyrimethamine [Chemical/Ingredient], Pyrimethamine product, Pyrimethamine (product), Pyrimethamine (substance) |
Swedish | Pyrimetamin |
Czech | pyrimethamin |
Finnish | Pyrimetamiini |
Russian | PIRIMETAMIN, KHLORIDIN, ПИРИМЕТАМИН, ХЛОРИДИН |
Japanese | ピリメタミン |
Polish | Pirymetamina, Daraprim |
Spanish | pirimetamina (producto), pirimetamina (sustancia), pirimetamina, Pirimetamina |
French | Pyriméthamine |
German | Pyrimethamin |
Italian | Pirimetamina |
Portuguese | Pirimetamina |
Ontology: Daraprim (C0591326)
Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
MSH | D011739 |
English | Daraprim, Glaxo Wellcome Brand of Pyrimethamine, GlaxoSmithKline Brand of Pyrimethamine, Wellcome Brand of Pyrimethamine |