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Pyrimethamine Side Effects

Medically reviewed on June 7, 2018

ConsumerProfessional Managing Side Effects

For the Consumer

Applies to pyrimethamine: oral tablet

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:

Less Common

  • Black, tarry stools
  • blood in urine or stools
  • cough or hoarseness
  • fever or chills
  • irritation or soreness of tongue
  • lower back or side pain
  • painful or difficult urination
  • pinpoint red spots on skin
  • unusual bleeding or bruising

Rare

  • Bleeding or crusting sores on lips
  • chest pain or discomfort
  • muscle cramps or pain
  • redness, blistering, peeling, or loosening of skin
  • skin rash
  • sores, ulcers, and/or white spots in mouth
  • sore throat
  • unusual tiredness or weakness

Frequency not known

  • Blood in urine
  • diarrhea
  • difficulty swallowing
  • dizziness
  • fainting spells
  • fast, slow, or irregular heartbeat
  • hives
  • itching
  • joint or muscle pain
  • lightheadedness
  • pale skin
  • pounding or rapid pulse
  • puffiness or swelling of the eyelids or around the eyes, face, lips or tongue
  • rapid breathing
  • red, irritated eyes
  • red skin lesions, often with a purple center
  • shortness of breath
  • swollen glands
  • tightness in chest
  • unexplained bleeding or bruising
  • wheezing

Symptoms of Overdose

  • Abdominal or stomach pain
  • convulsions (seizures)
  • increased excitability
  • vomiting (severe and continuing)

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:

Less Common

  • Diarrhea
  • loss of appetite
  • nausea
  • vomiting

For Healthcare Professionals

Applies to pyrimethamine: compounding powder, oral tablet

Gastrointestinal

Gastrointestinal side effects have included nausea, vomiting, diarrhea, glossitis, and atrophic glossitis, particularly with high doses. Gastrointestinal intolerance may be minimized by administering pyrimethamine with food.[Ref]

Hypersensitivity

Hypersensitivity reactions have been reported when pyrimethamine is administered with a sulfonamide. These reactions may be severe and include erythema multiforme, Stevens-Johnson Syndrome, toxic epidermal necrolysis, Lyell's syndrome, hepatitis, anaphylaxis, and pulmonary reactions. Fatal reactions have been estimated to occur in one of 11,000 to 25,000 patients treated. Hypersensitivity reactions have also been reported with pyrimethamine/clindamycin combinations and are usually limited to maculopapular rashes.[Ref]

Hematologic

Hematologic side effects have occurred, especially when large doses of pyrimethamine are administered. Thrombocytopenia, megaloblastic anemia, leukopenia, pancytopenia, agranulocytosis, and fatalities have been reported.[Ref]

Nervous system

Nervous system toxicity is problematic with higher dosages of pyrimethamine. Ataxia, tremors, and seizures may occur.[Ref]

Respiratory

Respiratory side effects have rarely included pulmonary eosinophilia.[Ref]

Cardiovascular

Cardiovascular side effects have included arrhythmias, particularly with high doses.[Ref]

Metabolic

Metabolic side effects have included hyperphenylalaninemia, particularly when pyrimethamine is given in combination with a sulfonamide.[Ref]

Oncologic

Oncologic side effects have included two reports of malignancy; both were associated with pyrimethamine treatment for toxoplasmosis: 1 patient developed chronic granulocytic leukemia after 2 years of therapy and 1 patient developed reticulum cell sarcoma after 14 months of therapy. Animal studies have revealed increased lung tumors with intraperitoneal administration.[Ref]

References

1. "Product Information. Daraprim (pyrimethamine)." Glaxo Wellcome, Research Triangle Park, NC.

2. Davidson AC, Bateman C, Shovlin C, Marrinan M, Burton GH, Cameron IR "Pulmonary toxicity of malaria prophylaxis." BMJ 297 (1988): 1240-1

3. Pang JA "Non-cardiogenic pulmonary oedema associated with pyrimethamine." Respir Med 83 (1989): 247-8

4. Bamber MG, Elder AT, Gray JA, Minns RA "Fatal Stevens-Johnson syndrome associated with Fansidar and chloroquine." J Infect 13 (1986): 31-3

5. Ortel B, Sivayathorn A, Honigsmann H "An unusual combination of phototoxicity and Stevens-Johnson syndrome due to antimalarial therapy." Dermatologica 178 (1989): 39-42

6. Whitfield D "Presumptive fatality due to pyrimethamine-sulfadoxine." Lancet 2 (1982): 1272

7. Olsen VV, Loft S, Christensen KD "Serious reactions during malaria prophylaxis with pyrimethamine- sulfadoxine." Lancet 2 (1982): 994

8. Hornstein OP, Ruprecht KW "Fansidar-induced Stevens-Johnson Syndrome." N Engl J Med 307 (1982): 1529-30

9. Selby CD, Ladusans EJ, Smith PG "Fatal multisystemic toxicity associated with prophylaxis with pyrimethamine and sulfadoxine (Fansidar)." Br Med J (Clin Res Ed) 290 (1985): 113-4

10. McCormack D, Morgan WK "Fansidar hypersensitivity pneumonitis." Br J Dis Chest 81 (1987): 194-6

11. Jeffrey RF "Transient lupus anticoagulant and fansidar therapy." Postgrad Med J 62 (1986): 893-4

12. "Fansidar-associated fatal reaction in an HIV-infected man." MMWR Morb Mortal Wkly Rep 37 (1988): 571-2

13. Phillips-Howard PA, West LJ "Serious adverse drug reactions to pyrimethamine-sulphadoxine pyrimethamine-dapsone and to amodiaquine in Britain." J R Soc Med 83 (1990): 82-5

14. Adams SJ, Broadbent J, Clayden LM, Ridley CM "Erythema multiforme (Stevens-Johnson) precipitated by Fansidar." Postgrad Med J 61 (1985): 263-4

15. Phillips-Howard PA, Behrens RH, Dunlop J "Stevens-Johnson syndrome due to pyrimethamine/sulfadoxine during presumptive self-therapy of malaria." Lancet 2 (1989): 803-4

16. Zitelli BJ, Alexander J, Taylor S, Miller KD, Howrie DL, Kuritsky JN, Perez TH, Van Thiel DH "Fatal hepatic necrosis due to pyrimethamine-sulfadoxine (Fansidar)." Ann Intern Med 106 (1987): 393-5

17. Ward DJ, Krzeminska EC, Tanner NS "Treatment of toxic epidermal necrolysis and a review of six cases." Burns 16 (1990): 97-104

18. Svanbom M, Rombo L, Gustafsson L "Unusual pulmonary reaction during short term prophylaxis with pyrimethamine-sulfadoxine (Fansidar)." Br Med J (Clin Res Ed) 288 (1984): 1876

19. Booth F, Barker LC, Barton CJ, Naik RB "Agranulocytosis during malaria prophylaxis with Maloprim (pyrimethamine and dapsone)." Postgrad Med J 60 (1984): 566-7

20. Bowcock SJ, Linch DC, Machin SJ, Stewart JW "Pyrimethamine in the myeloproliferative disorders: a forgotten treatment?" Clin Lab Haematol 9 (1987): 129-36

21. Nicholls MD, Concannon AJ "Maloprim-induced agranulocytosis and red-cell aplasia." Med J Aust 2 (1982): 564-6

22. Ree GH "Chemoprophylaxis of malaria in Africa." Br Med J (Clin Res Ed) 286 (1983): 562

23. Iaccheri B, Fiore T, Papadaki T, et al. "Adverse drug reactions to treatments for ocular toxoplasmosis: A retrospective chart review." Clin Ther 30 (2008): 2069-74

24. Whitehead S "Agranulocytosis associated with maloprim." Br Med J (Clin Res Ed) 286 (1983): 1515

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.

Medical Disclaimer

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