What is pyrimethamine?
Pyrimethamine is an antiparasitic prescription medicine approved by the U.S. Food and Drug Administration (FDA) for the treatment of toxoplasmosis (infection caused by the parasite Toxoplasma gondii) and acute malaria. When used to treat these diseases, pyrimethamine is usually used together with a sulfonamide medicine. Pyrimethamine is also FDA-approved for the prevention of certain types of malaria.
Toxoplasmosis of the brain (also called Toxoplasma gondii encephalitis) and malaria are opportunistic infections. An opportunistic infection is an infection that occurs more frequently or is more severe in people with weakened immune systems—such as those infected with HIV—than in people with healthy immune systems.
Pyrimethamine can also be used “off-label” to prevent and treat other opportunistic infections of HIV infection. “Off-label” use refers to use of an FDA-approved medicine in a manner different from that described on the medicine label. Good medical practice and the best interests of a patient sometimes require that a medicine be used “off-label.”
What HIV-related opportunistic infections is pyrimethamine used for?
The Guidelines for the Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescents, prepared by the Centers for Disease Control and Prevention (CDC), the National Institutes of Health (NIH), and the HIV Medicine Association of the Infectious Diseases Society of America (IDSA-HIVMA), includes recommendations on the HIV-related uses of pyrimethamine to:
- Pneumocystis pneumonia (PCP) from occurring the first time (called primary prophylaxis) and from recurring (called secondary prophylaxis or maintenance therapy). (This is an “off-label” use.)
- Toxoplasma gondii encephalitis from occurring the first time and from recurring. (This is an “off-label” use.)
- Isosporiasis (also known as Isospora belli infection) from recurring. (This is an “off-label” use.)
- Toxoplasma gondii encephalitis.
- Isosporiasis. (This is an “off-label” use.)
The above list may not include all of the HIV-related uses of pyrimethamine recommended in the Guidelines for the Prevention and Treatment of Opportunistic Infections in HIV-Infected Adults and Adolescents
. Some recommended uses, such as uses in certain rare circumstances, may have been omitted.
What should I tell my health care provider before taking pyrimethamine?
Before taking pyrimethamine, tell your health care provider:
- If you are allergic to pyrimethamine or any other medicines.
- About any medical conditions you have or have had, for example, diabetes or liver problems.
- About anything that could affect your ability to take medicines, such as difficulty swallowing or remembering to take pills.
- If you are pregnant or plan to become pregnant. Whether pyrimethamine can harm an unborn baby is unknown. Talk to your health care provider about possible risks with taking pyrimethamine when pregnant.
- If you are breastfeeding or plan to breastfeed. Do not breastfeed if you are infected with HIV.
- About other prescription and nonprescription medicines, vitamins, nutritional supplements, and herbal products you are taking or plan to take. Pyrimethamine may affect the way other medicines or products work, and other medicines or products may affect how pyrimethamine works. Ask your health care provider if there are interactions between pyrimethamine and the other medicines you take.
Ask your health care provider about possible side effects from pyrimethamine. Your health care provider will tell you what to do if you have side effects.
How should I take pyrimethamine?
Take pyrimethamine according to your health care provider’s instructions. Your health care provider will tell you how much pyrimethamine to take and when to take it. Before you start pyrimethamine and each time you get a refill, read any printed information that comes with your medicine.
How should pyrimethamine be stored?
- Store pyrimethamine at 59°F to 77°F (15°C to 25°C) and in a dry place.
- Protect pyrimethamine from light.
- Do not use pyrimethamine if the original seal over the bottle opening is broken or missing.
- Throw away pyrimethamine that is no longer needed or expired (out of date). Follow FDA guidelines on how to safely dispose of unused medicine.
- Keep pyrimethamine and all medicines out of reach of children.
Where can I find more information about pyrimethamine?
More information about pyrimethamine is available:
The above Patient Version drug summary is based on the following FDA label(s): Tablet
Last Reviewed: February 24, 2015
Last Updated: February 24, 2015