Pyrimethamine Side Effects
Medically reviewed by Drugs.com. Last updated on May 8, 2022.
For the Consumer
Applies to pyrimethamine: oral tablet
Side effects requiring immediate medical attention
Along with its needed effects, pyrimethamine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.
Check with your doctor immediately if any of the following side effects occur while taking pyrimethamine:
Rare
- Chest pain
- dry cough
- fever
- rapid or trouble breathing
- skin rash
- unusual tiredness or weakness
Incidence not known
- Black, tarry stools
- bleeding gums
- blistering, peeling, or loosening of the skin
- blood in the urine or stools
- chills
- cough
- diarrhea
- difficulty swallowing
- dizziness
- fainting spells
- fast or irregular heartbeat
- hives, itching
- irritation or soreness of the tongue
- joint or muscle pain
- lower back or side pain
- puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
- painful or difficult urination
- pale skin
- pinpoint red spots on the skin
- red, irritated eyes
- red skin lesions, often with a purple center
- sore throat
- sores, ulcers, or white spots on the lips or in the mouth
- swollen glands
- tightness in the chest
- unusual bleeding or bruising
Side effects not requiring immediate medical attention
Some side effects of pyrimethamine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.
Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:
Incidence not known
- Loss of appetite
- vomiting
- weight loss
For Healthcare Professionals
Applies to pyrimethamine: compounding powder, oral tablet
General
Since this drug is coadministered with a sulfonamide, the manufacturer product information for the relevant sulfonamide should be consulted for sulfonamide-related side effects.[Ref]
Gastrointestinal
Very common (10% or more): Nausea, vomiting, diarrhea, colic
Uncommon (0.1% to 1%): Dry mouth, dry throat
Very rare (less than 0.01%): Buccal ulceration
Frequency not reported: Glossitis, atrophic glossitis[Ref]
Nervous system
Precipitation of a grand mal attack in a patient predisposed to epilepsy was reported; clinical significance was not established.[Ref]
Very common (10% or more): Headache
Common (1% to 10%): Dizziness
Very rare (less than 0.01%): Convulsions/seizures
Frequency not reported: Ataxia, tremors, precipitation of grand mal attack[Ref]
Hematologic
Very common (10% or more): Anemia
Common (1% to 10%): Thrombocytopenia, leukopenia
Very rare (less than 0.01%): Pancytopenia
Frequency not reported: Megaloblastic anemia, neutropenia, agranulocytosis[Ref]
Dermatologic
Very common (10% or more): Rash
Uncommon (0.1% to 1%): Abnormal skin pigmentation, dermatitis
Other
Uncommon (0.1% to 1%): Fever, malaise
Psychiatric
Insomnia was reported when this drug was given weekly at higher than recommended doses.
Uncommon (0.1% to 1%): Depression
Very rare (less than 0.01%): Insomnia
Respiratory
Rare (0.01% to 0.1%): Pulmonary eosinophilia
Very rare (less than 0.01%): Pneumonia with cellular and eosinophilic pulmonary infiltration[Ref]
Pneumonia with cellular and eosinophilic pulmonary infiltration was observed when this drug was administered once a week with sulfadoxine.[Ref]
Hypersensitivity
Frequency not reported: Hypersensitivity reactions (included erythema multiforme, Stevens-Johnson Syndrome, toxic epidermal necrolysis, Lyell's syndrome, hepatitis, anaphylaxis, pulmonary reactions, maculopapular rashes)[Ref]
Cardiovascular
Circulatory collapse was reported in patients treated with higher than recommended doses.[Ref]
Very rare (less than 0.01%): Circulatory collapse
Frequency not reported: Disorders of cardiac rhythm, arrhythmias[Ref]
Metabolic
Hyperphenylalaninemia was reported in neonates treated for congenital toxoplasmosis.[Ref]
Very rare (less than 0.01%): Hyperphenylalaninemia
Frequency not reported: Anorexia[Ref]
Genitourinary
Very rare (less than 0.01%): Hematuria
Oncologic
A 51-year-old female developed chronic granulocytic leukemia after taking this drug for 2 years for toxoplasmosis and a 56-year-old patient developed reticulum cell sarcoma after taking this drug for 14 months for toxoplasmosis.[Ref]
Frequency not reported: Chronic granulocytic leukemia, reticulum cell sarcoma[Ref]
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- Drug class: miscellaneous antimalarials
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References
1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
2. Cerner Multum, Inc. "Australian Product Information." O 0
3. "Product Information. Daraprim (pyrimethamine)." Glaxo Wellcome (2001):
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6. Christensen KD, Olsen VV, Loft S "Serious reactions during malaria prophylaxis with pyrimethamine- sulfadoxine." Lancet 2 (1982): 994
7. Concannon AJ, Nicholls MD "Maloprim-induced agranulocytosis and red-cell aplasia." Med J Aust 2 (1982): 564-6
8. Barker LC, Barton CJ, Naik RB, Booth F "Agranulocytosis during malaria prophylaxis with Maloprim (pyrimethamine and dapsone)." Postgrad Med J 60 (1984): 566-7
9. Bowcock SJ, Linch DC, Stewart JW, Machin SJ "Pyrimethamine in the myeloproliferative disorders: a forgotten treatment?" Clin Lab Haematol 9 (1987): 129-36
10. Whitehead S "Agranulocytosis associated with maloprim." Br Med J (Clin Res Ed) 286 (1983): 1515
11. Fiore T, Iaccheri B, Papadaki T, et al. "Adverse drug reactions to treatments for ocular toxoplasmosis: A retrospective chart review." Clin Ther 30 (2008): 2069-74
12. Alexander J, Taylor S, Kuritsky JN, Miller KD, Perez TH, Howrie DL, Van Thiel DH, Zitelli BJ "Fatal hepatic necrosis due to pyrimethamine-sulfadoxine (Fansidar)." Ann Intern Med 106 (1987): 393-5
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14. Ladusans EJ, Smith PG, Selby CD "Fatal multisystemic toxicity associated with prophylaxis with pyrimethamine and sulfadoxine (Fansidar)." Br Med J (Clin Res Ed) 290 (1985): 113-4
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16. Whitfield D "Presumptive fatality due to pyrimethamine-sulfadoxine." Lancet 2 (1982): 1272
17. Behrens RH, Dunlop J, Phillips-Howard PA "Stevens-Johnson syndrome due to pyrimethamine/sulfadoxine during presumptive self-therapy of malaria." Lancet 2 (1989): 803-4
18. "Fansidar-associated fatal reaction in an HIV-infected man." MMWR Morb Mortal Wkly Rep 37 (1988): 571-2
19. Hornstein OP, Ruprecht KW "Fansidar-induced Stevens-Johnson Syndrome." N Engl J Med 307 (1982): 1529-30
20. Jeffrey RF "Transient lupus anticoagulant and fansidar therapy." Postgrad Med J 62 (1986): 893-4
21. Adams SJ, Broadbent J, Clayden LM, Ridley CM "Erythema multiforme (Stevens-Johnson) precipitated by Fansidar." Postgrad Med J 61 (1985): 263-4
22. McCormack D, Morgan WK "Fansidar hypersensitivity pneumonitis." Br J Dis Chest 81 (1987): 194-6
23. Tanner NS, Ward DJ, Krzeminska EC "Treatment of toxic epidermal necrolysis and a review of six cases." Burns 16 (1990): 97-104
24. Sivayathorn A, Honigsmann H, Ortel B "An unusual combination of phototoxicity and Stevens-Johnson syndrome due to antimalarial therapy." Dermatologica 178 (1989): 39-42
25. Bamber MG, Elder AT, Gray JA, Minns RA "Fatal Stevens-Johnson syndrome associated with Fansidar and chloroquine." J Infect 13 (1986): 31-3
26. Pang JA "Non-cardiogenic pulmonary oedema associated with pyrimethamine." Respir Med 83 (1989): 247-8
Further information
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Some side effects may not be reported. You may report them to the FDA.