You should not use this medicine if you have had an allergic reaction to pyrimethamine or if you have a severe type of blood disease (megaloblastic anemia) caused by not having enough folic acid in your body.
If you are pregnant or breastfeeding, talk to your doctor before taking this medicine. You may need to stop breastfeeding while taking this medicine.
Talk to your doctor before taking this medicine if you have seizures, any blood disorders, kidney disease, liver disease, or a history of alcoholism.
If you develop a skin rash, stop taking this medicine and call your doctor right away.
This medicine may help prevent malaria, but is not used to treat a severe attack of malaria.
Pyrimethamine may cause harmful side effects. To help treat these side effects, you may also be given another medicine called leucovorin. It is important that you take leucovorin exactly as your doctor ordered. Do not skip any doses.