Drug interactions
Folic acid + Pyrimethamine
Severity: Moderate
Folic acid and Pyrimethamine: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
Pyrimethamine inhibits parasitic dihydrofolate reductase, and supplemental folic acid can reduce its antiparasitic effect. For toxoplasmosis this may lead to treatment failure. Folinic acid is usually used instead to protect the marrow without blunting efficacy.
What this interaction means in plain words
Folic acid and Pyrimethamine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Folic acid belongs to Miscellaneous; Pyrimethamine belongs to Anti Parasitic.
Why it happens
Pharmacodynamic antagonism, as folic acid supplies the folate end-product whose synthesis pyrimethamine blocks.
What to do
Avoid folic acid supplementation during pyrimethamine treatment of toxoplasmosis and give folinic acid (leucovorin) to prevent haematological toxicity. Monitor blood counts.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Pyrimethamine
- Deferiprone + Pyrimethamine Major
- Eliglustat + Pyrimethamine Major
- Acalabrutinib + Pyrimethamine Moderate
- Brexpiprazole + Pyrimethamine Moderate
- Dapsone + Pyrimethamine Moderate
- Fosphenytoin + Pyrimethamine Moderate
Other interactions of Folic acid
- Ethotoin + Folic acid Moderate
- Folic acid + Fosphenytoin Moderate
- Folic acid + Glucarpidase Moderate
- Folic acid + Methotrexate Moderate
- Folic acid + Pafolacianine Moderate
- Folic acid + Phenobarbital Moderate
Frequently asked questions
Can I take Folic acid with Pyrimethamine?
MediHelp rates the interaction as moderate. Folic acid and Pyrimethamine can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. Pyrimethamine inhibits parasitic dihydrofolate reductase, and supplemental folic acid can reduce its antiparasitic effect. For toxoplasmosis this may lead to treatment failure. Folinic acid is usually used instead to protect the marrow without blunting efficacy.
How serious is the interaction between Folic acid and Pyrimethamine?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Avoid folic acid supplementation during pyrimethamine treatment of toxoplasmosis and give folinic acid (leucovorin) to prevent haematological toxicity. Monitor blood counts.
What other medicines interact with Pyrimethamine?
MediHelp also lists interactions of Pyrimethamine with, for example, Deferiprone, Eliglustat, Acalabrutinib. The full list is on the Pyrimethamine page.
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