Pyrimethamine
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Drug Status
Government Approvals
US(FDA), UK(BNF)
WHO Essential Medicine
YES
Known Teratogen
Possible
Pharmaceutical Class
Dihydrofolate Reductase Inhibitor Antimalarial
Controlled Drug Substance
NO
Pyrimethamine
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Click HereSummary
Pyrimethamine is primarily used to treat toxoplasmosis, an infection caused by the Toxoplasma parasite. It is often used in combination with a sulfonamide for enhanced effectiveness.
Pyrimethamine works by inhibiting an enzyme called dihydrofolate reductase, which is crucial for folic acid metabolism in parasites. This prevents the parasites from synthesizing nucleic acids necessary for their growth and reproduction, effectively controlling the infection.
For adults, the usual daily dose of Pyrimethamine is 50 to 75 mg taken with a sulfonamide. For children, the dose is 1 mg/kg/day divided into two equal daily doses. This dose may be reduced by half after 2 to 4 days and continued for about a month.
Common side effects of Pyrimethamine include anorexia (decreased appetite) and vomiting. Serious adverse effects can include hypersensitivity reactions, megaloblastic anemia, leukopenia (low white blood cell count), and thrombocytopenia (low platelet count).
Pyrimethamine is contraindicated in patients with hypersensitivity to the drug or its components, and in those with megaloblastic anemia due to folate deficiency. It may be carcinogenic and should be kept out of children's reach due to overdose risks.
Indications and Purpose
What is Pyrimethamine used for?
Pyrimethamine is primarily indicated for the treatment of toxoplasmosis, especially when used in combination with a sulfonamide. It is effective in treating infections caused by the Toxoplasma parasite.
How does Pyrimethamine work?
Pyrimethamine works by inhibiting the enzyme dihydrofolate reductase, which is crucial for folic acid metabolism in parasites. This inhibition prevents the parasites from synthesizing nucleic acids necessary for their growth and reproduction, effectively controlling the infection.
Is Pyrimethamine effective?
Pyrimethamine is an antiparasitic medication that works by inhibiting folic acid metabolism in parasites like Toxoplasma. Its effectiveness is enhanced when used with sulfonamides, as demonstrated in studies on experimental toxoplasmosis in mice and rabbits. Always consult a healthcare provider for personalized advice.
How does one know if Pyrimethamine is working?
The benefit of pyrimethamine is evaluated by monitoring the patient's response to treatment, including symptom improvement and tolerance to the medication. Regular blood tests may be conducted to check for side effects, especially in high doses. Always consult a healthcare provider for personalized advice.
Directions for Use
What is the usual dose of Pyrimethamine?
For adults, the usual daily dose of pyrimethamine is 50 to 75 mg, taken with a sulfonamide. For children, the dose is 1 mg/kg/day, divided into two equal daily doses. After 2 to 4 days, this dose may be reduced to half and continued for about a month. Always follow your doctor's specific instructions.
How do I take Pyrimethamine?
Pyrimethamine can be taken with meals to minimize gastrointestinal side effects like vomiting. There are no specific food restrictions mentioned, but always follow your doctor's instructions and consult them for personalized advice.
For how long do I take Pyrimethamine?
Pyrimethamine is typically used for 1 to 3 weeks initially, depending on the patient's response and tolerance. The dosage may then be reduced and continued for an additional 4 to 5 weeks. Always follow your doctor's specific instructions.
How long does it take for Pyrimethamine to start working?
Pyrimethamine is well absorbed, with peak levels occurring between 2 to 6 hours after administration. However, the time it takes to notice an improvement in symptoms can vary. Always consult a healthcare provider for personalized advice.
How should I store Pyrimethamine?
Pyrimethamine should be stored at a temperature between 15° to 25°C (59° to 77°F) in a dry place and protected from light. Always keep it out of reach of children.
Warnings and Precautions
Who should avoid taking Pyrimethamine?
Pyrimethamine is contraindicated in patients with hypersensitivity to the drug or its components, and in those with megaloblastic anemia due to folate deficiency. It has a narrow therapeutic window, and folate deficiency signs require dosage adjustment or discontinuation. It may be carcinogenic and should be kept out of children's reach due to overdose risks. Always consult a healthcare provider for personalized advice.
Can I take Pyrimethamine with other prescription drugs?
Pyrimethamine may interact with sulfonamides, quinine, and other antimalarials. It can increase the risk of bone marrow suppression when used with antifolic drugs or agents associated with myelosuppression, such as methotrexate. Mild hepatotoxicity has been reported with lorazepam. Always consult a healthcare provider for personalized advice.
Can I take Pyrimethamine with vitamins or supplements?
Pyrimethamine can cause folate deficiency, so concurrent administration of folinic acid (leucovorin) is recommended to prevent bone marrow suppression. Always consult a healthcare provider for personalized advice.
Can Pyrimethamine be taken safely while pregnant?
Pyrimethamine should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. It has been shown to be teratogenic in animal studies. Concurrent administration of folinic acid is strongly recommended during pregnancy. Always consult a healthcare provider for personalized advice.
Can Pyrimethamine be taken safely while breastfeeding?
Pyrimethamine is excreted in human milk, and due to potential serious adverse reactions in nursing infants, a decision should be made to either discontinue nursing or the drug. Always consult a healthcare provider for personalized advice.
Is Pyrimethamine safe for the elderly?
For elderly patients, dose selection should be cautious, usually starting at the low end of the dosing range. This is due to the greater frequency of decreased hepatic, renal, or cardiac function, and the presence of other diseases or drug therapies. Always consult a healthcare provider for personalized advice.
Is it safe to exercise while taking Pyrimethamine?
From all available and reliable information, there is no confirmed data on this. Please consult a doctor for personalized advice.
Is it safe to drink alcohol while taking Pyrimethamine?
From all available and reliable information, there is no confirmed data on this. Please consult a doctor for personalized advice.
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