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Pyrimethamine Side Effects

For the Consumer

Applies to pyrimethamine: oral tablet

As well as its needed effects, pyrimethamine may cause unwanted side effects that require medical attention.

Major Side Effects

If any of the following side effects occur while taking pyrimethamine, check with your doctor immediately:

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)

Minor Side Effects

Some pyrimethamine side effects may not need any medical attention. As your body gets used to the medicine these side effects may disappear. Your health care professional may be able to help you prevent or reduce these side effects, but do check with them if any of the following side effects continue, or if you are concerned 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. Whitfield D "Presumptive fatality due to pyrimethamine-sulfadoxine." Lancet 2 (1982): 1272

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

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

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

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

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

11. 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

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

13. 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

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

15. 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

16. 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

17. 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

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

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

22. 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

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

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

It is possible that some side effects of pyrimethamine may not have been reported. These can be reported to the FDA here. Always consult a healthcare professional for medical advice.

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