Pyrimethamine: Uses, Dosage, Price, Side Effects, Precautions & More
Pyrimethamine: Uses, Dosage, Price, Side Effects, Precautions & More

What is Pyrimethamine?

  • Pyrimethamine belongs to group of medicines known to have anti-parasitic actions
  • Pyrimethamine is available in tablet form (25mg).
  • It is drug of choice for prevention, treatment and control of:
  • Treatment of toxoplasmosis (infection of brain caused by parasite)
  • Treatment of acute malaria
  • Chemoprophylaxis of malaria
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Uses of Pyrimethamine

  • Pyrimethamine is used to kill or prevent growth of parasites.
  • Pyrimethamine may be used alone or in conjugation with other drugs like sulfadoxine.
Also Read: Seacod Capsule Uses | Septillin Uses | Stugeron Uses

How does Pyrimethamine work?

  • Pyrimethamine acts as dihydrofolate reductase inhibitor which inhibits the enzyme dihydrofolate reductase present in plasmodium parasite and thereby blocks its DNA synthesis and cell multiplication resulting in death of parasite in the body.

Pyrimethamine Price in India

SpecificsPyrimethamine Price
500 mg Strip of 10 TabletsRs 57.00
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How to Take Pyrimethamine?

  • The dosage and duration of Pyrimethamine intake should be decided by the doctor. Do not take more than or less than the recommended dose.
  • Pyrimethamine should be taken with food to avoid gastric side effects but at a fixed time everyday.
  • The tablet can be swallowed as a whole without crushing or chewing it.
  • Drink plenty of fluids to prevent kidney stones formation in patients taking this medicine.
  • Pyrimethamine should not be stopped in between without doctor’s consent and before the course of the therapy is not completed even if symptoms have disappeared as infection may reappear.

Common Dosage for Pyrimethamine?

  • The optimum dosage of Pyrimethamine varies with the type of the parasitic infection, age of the patient and initial response to the drug.
  • The dose should be adjusted in such a way that it should have maximum therapeutic outcome and minimal side effects.
  • Starting dose for adults suffering from toxoplasmosis is 50-75mg daily along with 1-4gm of sulfadoxine for 1-3 weeks. Dose can then be gradually deceased to half and continued for another 4-5 weeks.
  • For chemoprophylaxis of malaria in adults, 25mg tablet once a week. In children (4-10 years), 12.5mg (Half tablet) once in a week.
  • In case of non improvement of symptoms or symptoms getting worse, seek medical attention immediately.

When to Avoid Pyrimethamine?

  • Pyrimethamine should be avoided or used with caution in:
  • Allergy to any of its components
  • Patients with severe liver and kidney disease (consult your physician in such case)
  • Patients with folic acid deficiency
  • Patients with megaloblastic anemia
  • Pregnant and breast feeding women

Side-effects of Pyrimethamine?

Although Pyrimethamine is well absorbed orally, few reported side effects include:

  • Nausea
  • Vomiting
  • Abdominal pain
  • Loss of appetite
  • Neutropenia (decreased neutrophil count)
  • Headache
  • Muscle weakness

In addition, it may also cause some allergic or unwanted effects like skin rash, seizures, hallucinations, jaundice etc. In such cases, seek medical attention immediately.

Also Read: Promethazine Side Effect 

Effect on organs?

  • No such adverse effect observed on any organ.

Reported Allergic Reactions?

Report to your doctor if you are allergic to any of the ingredients of Pyrimethamine or any other sulphur drugs.

Signs of allergic reaction include:

  • Rashes/itching of skin
  • Shortness of breath
  • Swelling of face, lips, tongue, or throat
  • Loss of consciousness

Drug Interactions to Be Careful About

  • Many medicines when taken along side some other drug have shown some interaction, resulting in decreased therapeutic effects and increased chances of side effects.
  • It is always advised that the patient must inform the physician about all the drugs/over the counter products/vitamin supplements being used along with Pyrimethamine.
  • All the possible drug interactions might not be listed here. Pyrimethamine may interact with the following drugs and products:
  • Quinine
  • Lorazepam
  • Trimethoprim
  • Warfarin
  • Zidovudine
  • Other sulfa drugs

Shows Effects / Results In:

  • Pyrimethamine is rapidly absorbed orally with peak absorption occurring within 6 hours of oral administration.


Is Pyrimethamine addictive?

  • No such tendency has been reported.

Can I have Pyrimethamine with alcohol?

  • Interaction with alcohol is unknown. Consult your doctor before consumption.

Any particular food item to be avoided?

  • No such interaction seen with any food product.

Can I have Pyrimethamine when pregnant?

  • Always inform your doctor if you are pregnant or plan to become pregnant.
  • Pyrimethamine is not recommended for use during pregnancy as it may harm the developing fetus. It should only be taken if the benefits outweigh the risks.

Can I have Pyrimethamine when feeding a baby?

  • Safety of Pyrimethamine is not known while you are breast feeding your baby thus avoid its use while breastfeeding.
  • Always inform and consult your doctor if you are taking Pyrimethamine while breast-feeding your child.

Can I drive after taking Pyrimethamine?

  • Pyrimethamine doesn’t usually affect your ability to drive. However few patients on may experience side effects like headache and dizziness.
  • Caution must be exercised in such patients while driving and operating heavy machinery.

What happens if I overdose on Pyrimethamine?

  • It should not be administered in more than recommended dose as it may have deleterious effects.
  • Signs of over dosage: severe abdominal pain, vomiting, convulsions, respiratory depression, circulatory collapse etc.
  • Patients suspected of over-dosage should seek medical care immediately.

What happens if I take expired Pyrimethamine?

  • Taking a single expired dose may not cause any major adverse effect. However, the potency of the medicine may well have been reduced and it might not be effective against the parasitic infection.

What happens if I miss a dose of Pyrimethamine ?

  • Always consume the missed dose as soon as you remember it. But, if it’s already time to take the second dose after that – do not take double dose.

Storage of Pyrimethamine

Stored at room temperature away from direct sunlight and heat.

Keep medicines away from children and pets.

Pro Tips When Taking Pyrimethamine:

  • Regular monitoring of blood should be done in patients taking high doses of pyrimethamine as decreased platelet count, RBC Count or WBC count can be seen as an adverse effect.
  • Folic acid deficiency can occur in patients taking high doses of pyrimethamine. Thus Folic acid can be given as an adjuvant in such patients.

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