n.
A drug, C12H13ClN4, used principally in the prophylactic treatment of malaria.
[PYRIM(IDINE) + ETH(YL) + AMINE.]
pyrimethamine
Dictionary:
py·ri·meth·a·mine (pī'rə-mĕth'ə-mēn', -mĭn) 
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n.
A drug, C12H13ClN4, used principally in the prophylactic treatment of malaria.
| 5min Related Video: pyrimethamine |
| Dental Dictionary: pyrimethamine |
(pir′meth′ə-mēn)
n
n
A folic acid inhibitor that acts against Toxoplasma gondii and Plasmodium spp., which cause toxoplasmosis and malaria.
| Drug Info: Pyrimethamine |
Brand names: Daraprim®
Chemical formula:
- Drug Forms:
- Pyrimethamine tablets (below)
- Pyrimethamine Oral tablet
Pyrimethamine tablets
What are pyrimethamine tablets?
PYRIMETHAMINE (Daraprim®) is an antiparasitic agent. It is used to help prevent or treat malaria or can be used to treat toxoplasmosis. Pyrimethamine can also be used to treat Pneumocystis carinii pneumonia, if you cannot take more standard treatment. Generic pyrimethamine tablets are not yet available.
What should I tell my health care provider before I take this medicine?
They need to know if you have any of these conditions:
• an alcohol problem
• anemia or other blood disorders
• asthma
• dental disease
• folic acid deficiency
• kidney disease
• liver disease
• seizures (convulsions)
• an unusual or allergic reaction to pyrimethamine, other medicines, foods, dyes, or preservatives
• pregnant or trying to get pregnant
• breast-feeding
How should I take this medicine?
Take pyrimethamine tablets by mouth. Follow the directions on the prescription label. Swallow tablets whole with a drink of water. If pyrimethamine upsets your stomach take it with food or milk. Take your doses at regular intervals. Do not take your medicine more often than directed.
What drug(s) may interact with pyrimethamine?
• medicines for HIV infection
• carbamazepine
• folic acid, folinic acid
• p-aminobenzoic acid, PABA
• lorazepam
• medicines for cancer chemotherapy
• medicines for mental problems and psychotic disturbances
• medicines for an over-active thyroid gland
• procainamide
• some antibiotics
Tell your prescriber or health care professional about all other medicines you are taking, including non-prescription medicines, nutritional supplements, or herbal products. Also tell your prescriber or health care professional if you are a frequent user of drinks with caffeine or alcohol, if you smoke, or if you use illegal drugs. These may affect the way your medicine works. Check with your health care professional before stopping or starting any of your medicines.
What should I watch for while taking pyrimethamine?
Tell your prescriber or health care professional if your symptoms do not improve in 2 to 3 days. High doses of pyrimethamine for toxoplasmosis can cause blood problems; visit your prescriber or health care professional for regular checks on your blood.
If you get a skin rash, stop taking your medicine and consult your prescriber or health care professional as soon as you can.
Pyrimethamine can cause blood problems. This can mean slow healing and a risk of infection. Try to avoid cutting or injuring yourself. Problems can arise if you need dental work, and in the day to day care of your teeth. Try to avoid damage to your teeth and gums when you brush or floss your teeth.
Check with your pharmacist before you visit a new area where there are malaria-carrying mosquitoes. You may need to take a different antimalarial medicine.
What side effects may I notice from taking pyrimethamine?
Side effects that you should report to your prescriber or health care professional as soon as possible:
• difficulty breathing
• fever or chills, sore throat
• increased sensitivity to the sun or ultraviolet light
• sore mouth or odd taste, swollen tongue
• seizures (convulsions)
• redness, blistering, peeling, or loosening of skin, including skin inside the mouth
• skin rash, itching
• stomach pain
• unusual bleeding or bruising
• unusual tiredness or weakness
Side effects that usually do not require medical attention (report to your prescriber or health care professional if they continue or are bothersome):
• diarrhea
• loss of appetite
• nausea, vomiting
Where can I keep my medicine?
Keep out of the reach of children in a container that small children cannot open. It is important to keep pyrimethamine out of reach of children; overdose is dangerous.
Store at room temperature between 15 and 25 degrees C (59 and 77 degrees F). Protect from light and moisture. Keep container tightly closed. Throw away any unused medicine after the expiration date.
Last updated: 7/1/2002
Important Disclaimer: The drug information provided here is for educational purposes only. It is intended to supplement, not substitute for, the diagnosis, treatment and advice of a medical professional. This drug information does not cover all possible uses, precautions, side effects and interactions. It should not be construed to indicate that this or any drug is safe for you. Consult your medical professional for guidance before using any prescription or over the counter drugs.
| Veterinary Dictionary: pyrimethamine |
A folic acid antagonist used in combination with sulfonamides in the treatment of toxoplasmosis and avian coccidiosis.
| Wikipedia: Pyrimethamine |
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Pyrimethamine
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| Systematic (IUPAC) name | |
| 5-(4-chlorophenyl)-6-ethyl- 2,4-pyrimidinediamine | |
| Identifiers | |
| CAS number | 58-14-0 |
| ATC code | P01BD01 |
| PubChem | 4993 |
| DrugBank | APRD00599 |
| Chemical data | |
| Formula | C12H13ClN4 |
| Mol. mass | 248.71 g/mol |
| Pharmacokinetic data | |
| Bioavailability | well-absorbed |
| Protein binding | 87% |
| Metabolism | Hepatic |
| Half life | 96 hours |
| Excretion | Renal |
| Therapeutic considerations | |
| Pregnancy cat. | |
| Legal status |
℞ Prescription only |
| Routes | Oral |
 (what is this?) (verify) |
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Pyrimethamine (Daraprim) is a medication used for protozoal infections. It is commonly used as an antimalarial drug (for both treatment and prevention of malaria), and is also used (combined with sulfadiazine) in the treatment of Toxoplasma gondii infections in immunocompromised patients, such as HIV-positive individuals.
Contents |
Mechanism of action
Pyrimethamine interferes with folic acid synthesis by inhibiting the enzyme dihydrofolate reductase (DHFR). Folic acid is needed for DNA and RNA synthesis in many species, including protozoa.
Mechanism of resistance
Resistance to pyrimethamine is widespread. Mutations in the malarial gene for dihydrofolate reductase may reduce the effectiveness of pyrimethamine[1]. These mutations decrease the binding affinity between pyrimethamine and dihydrofolate reductase via loss of hydrogen bonds and steric interactions[2].
Clinical use
Pyrimethamine is typically given with a sulfonamide and folinic acid:
- Sulfonamides inhibit dihydropteroate synthetase, an enzyme that participates in folic acid synthesis from para-aminobenzoic acid. Hence, sulfonamides work synergistically[citation needed] with pyrimethamine by blocking a different enzyme needed for folic acid synthesis.
- Folinic acid (Leucovorin) is a compound that can be converted into folic acid by the human body (but not by protozoa?) without relying on dihydrofolate reductase. By doing so, folinic acid reduces side effects related to folate deficiency.
Use in mass drug administrations
Pyrimethamine has been extensively used as monotherapy in mass drug administrations in Asia and South America which is likely to have contributed to the emergence and spread of pyrimethamine resistant Plasmodium falciparum strains.
Side effects
Pyrimethamine may deplete folic acid in humans, resulting in hematologic side effects associated with folate deficiency.
Side effects include:
- hypersensitivity reactions
- megaloblastic anemia
- leukopenia
- thrombocytopenia
- pancytopenia
- atrophic glossitis
- hematuria
- cardiac arrhythmias
- pulmonary eosinophilia (rare)
- hyperphenylalaninemia (particularly when used with a sulfonamide)
- Steven-Johnson syndrome (particularly when used with a sulfonamide)
- toxic epidermal necrolysis (particularly when used with a sulfonamide)
Contraindications
Pyrimethamine is contraindicated in patients with:
- hypersensitivity to pyrimethamine
- megaloblastic anemia – depletion of folic acid may aggravate this condition
Notes
- ^ Gatton M.L. et al. (2004). "Evolution of resistance to sulfadoxine-pyrimethamine in Plasmodium falciparum". Antimicrob Agents Chemother 48 (6): 2116–23. doi:. PMID 15155209.
- ^ Sirichaiwat C. et al. (2004). "Target guided synthesis of 5-benzyl-2,4-diamonopyrimidines: their antimalarial activities and binding affinities to wild type and mutant dihydrofolate reductases from Plasmodium falciparum". J Med Chem 47 (2): 345–54. doi:. PMID 14711307.
References
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 | Pyrimethamine; Sulfadoxine |
| trimethoprim |
| diaminopyrimidines |
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 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved. Read more |
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| Dental Dictionary. Mosby's Dental Dictionary. Copyright © 2004 by Elsevier, Inc. All rights reserved. Read more |
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| Drug Info. Gold Standard. Copyright © 2008 by Gold Standard. All rights reserved. Read more |
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| Veterinary Dictionary. Saunders Comprehensive Veterinary Dictionary 3rd Edition. Copyright © 2007 by D.C. Blood, V.P. Studdert and C.C. Gay, Elsevier. All rights reserved. Read more |
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