Pyrimethamine - oral

Patient Medicine Information
Why do I need this medicine?
Pyrimethamine is used together with other medicines to treat infections caused by a parasite called Toxoplasma.
How do I take this medicine?
Take Pyrimethamine exactly as directed by your doctor or according to the instructions on the label. Do not take more or less than instructed by your doctor.

Take it together with food or immediately after a meal. Try to take it at the same time each day.

Take Pyrimethamine at regular intervals. Do not skip any doses. You must complete the entire course of this medicine. If you don't, the infection will not be properly controlled.

The dose of this medicine will be decided by your doctor. Your doctor will advise you on the treatment timeframe depending on the type and severity of your condition.
What should I do if I have forgotten to take this medicine?
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and return to your normal dosing schedule.

DO NOT double a dose under any circumstances.

If you often forget to take your medicine, let your doctor and pharmacist know.
When should I not use this medicine?
Alert your doctor if you have megaloblastic anaemia (a disorder affecting the red blood cells) as Pyrimethamine may not be suitable for you.

Do not take Pyrimethamine if you ever had an allergic reaction (e.g. rashes, breathlessness, swollen eyes) to this medicine or any of its ingredients.

Do not take Pyrimethamine during the 1st trimester of your pregnancy or if you are breastfeeding.
What should I take note of while taking this medicine?
Inform your doctor if you have the following conditions:
  • fits or seizures
  • G6PD deficiency (an inherited blood disorder that affects the red blood cell)
  • folate deficiency
  • alcoholism
  • liver disease
  • kidney disease
Be sure to check with your doctor or pharmacist before giving this medicine to a child. Children may be more sensitive to the side effects.

This medicine may cause the level of your platelets to drop.

Platelets help your blood to clot when there is a cut in the skin. A fall in the level of your platelets may put you at risk of bleeding more than usual. Do not take part in activities where you may fall or get injured, such as contact sports. Inform your doctor if you get any unusual bruising (large bruises or several bruises, especially if the bruises appeared on their own) or bleeding that takes a long time to stop (for example, too much bleeding when you floss or brush your teeth).

For as long as you are taking this medicine, you may need to have regular blood tests (e.g. CBC, platelets, liver and kidney function) to check your body’s response to the medicine. Your doctor will advise you about how often you need to have these tests.
What side effects could I experience?
Pyrimethamine may cause any of the following side effects: nausea, vomiting, diarrhoea, fever, headache, dizziness, and rash.

If you develop rashes, breathlessness, swollen mouth or eyes, stop taking Pyrimethamine and inform your doctor immediately. These could be signs of an allergic reaction.

Inform your doctor if any of these side effects do not go away or are severe, or if you experience other side effects.
Can I take this with other medicines?
Inform your doctor and pharmacist if you are taking any of these medicines:
  • certain antibiotics e.g. co-trimoxazole, sulfadiazine
  • medicines for mood disorders e.g. lorazepam
  • medicines used to treat malaria e.g. quinine
  • medicines to treat viral infections e.g. zidovudine
  • antacids (medicines that reduces stomach acid production)
This list does not include all medicines that may interact with Pyrimethamine.

Always notify your doctor and pharmacist if you are taking any other medicines, including herbal tonics such as traditional Chinese medicines, supplements and medicines that you buy without a prescription.
What special dietary instructions should I follow?
Avoid alcohol.
How should I store this medicine?
Store in a cool, dry place away from the reach of children.

Protect from light.

Medicines must not be used past the expiry date.
This information is independently developed by MIMS based on pyrimethamine - oral and is provided for your reference only. It is not a replacement for and should only be used in conjunction with full consultation with a licensed healthcare professional, the information provided by your pharmacist and/or the manufacturer of the medication. It may not contain all the available information you require and cannot substitute professional medical care, nor does it take into account all individual circumstances. Although great effort has been made to ensure content accuracy, we shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2021 MIMS. All rights reserved. Powered by
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