Fansidar Side Effects

Generic name: pyrimethamine / sulfadoxine

Medically reviewed by Drugs.com. Last updated on Feb 28, 2025.

Note: This document provides detailed information about Fansidar Side Effects associated with pyrimethamine / sulfadoxine. Some dosage forms listed on this page may not apply specifically to the brand name Fansidar.

Applies to pyrimethamine / sulfadoxine: oral tablet.

Get emergency medical help if you have any of these signs of an allergic reaction while taking pyrimethamine / sulfadoxine: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Stop using pyrimethamine and sulfadoxine and call your doctor at once if you have any of these serious side effects:

• the first sign of any skin rash, no matter how mild;

• a severe blistering, peeling, and red skin rash;

• pale skin, easy bruising or bleeding;

• feeling tired, weak, or dizzy;

• hallucinations, seizure (convulsions);

• urinating less than usual or not at all;

• jaundice (yellowing of the skin or eyes); or

• fever, chills, sore throat, swollen tongue, joint pain, cough, feeling short of breath.

Less serious side effects of pyrimethamine / sulfadoxine may include:

• mild stomach pain, feeling full;

• slight hair loss;

• headache;

• muscle weakness;

• depression, nervousness;

• ringing in your ears; or

• sleep problems (insomnia).

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.

For healthcare professionals

Applies to pyrimethamine / sulfadoxine: oral tablet.

Hypersensitivity adverse events

Hypersensitivity reactions have included erythema multiforme, Stevens-Johnson syndrome, generalized skin eruptions, toxic epidermal necrolysis, urticaria, serum sickness, pruritus, exfoliative dermatitis, anaphylactoid reactions, periorbital edema, conjunctival and scleral injection, photosensitization, arthralgia, and allergic pericarditis. Fatalities due to severe hypersensitivity reactions have been reported.^[Ref]

Severe cutaneous reactions have occurred in patients who have taken as few as two doses of pyrimethamine-sulfadoxine. The risk of fatal cutaneous reactions in patients receiving pyrimethamine-sulfadoxine has been estimated to range from 1 in 11,000 to 1 in 25,000. In general, the use of sulfonamide antibiotics is associated with large increases in the risk of Stevens-Johnson syndrome or toxic epidermal necrolysis, although these phenomena are rare as a whole.^[Ref]

Dermatologic

Dermatologic side effects have frequently included phototoxicity, rash, dermatitis, and hair loss.^[Ref]

Hematologic

Hematologic side effects have included leucopenia (7%), agranulocytosis, aplastic anemia, megaloblastic anemia, thrombocytopenia, hemolytic anemia, purpura, hypoprothrombinemia, methemoglobinemia, and eosinophilia. Macrocytic anemia has also been reported. Fatalities have been reported.^[Ref]

Hematologic toxicity is more common with higher doses of pyrimethamine.

Many cases of agranulocytosis have occurred during therapy with pyrimethamine-dapsone, although it has been reported in patients receiving pyrimethamine-sulfadoxine as well.^[Ref]

Gastrointestinal

Gastrointestinal side effects have included anorexia (5.5%), digestive intolerance (3%), diarrhea (2.74%), abdominal pain (2.74%), vomiting (2.74%), nausea, glossitis, stomatitis, and pancreatitis.^[Ref]

Hepatic

Hepatic side effects have included hepatitis (7%), hepatocellular necrosis, and liver enzyme elevations.^[Ref]

In many cases, the hepatitis has accompanied severe cutaneous reactions, fever, myalgias and arthralgias. Granulomas and necrosis have been seen on biopsy.^[Ref]

Renal

Renal side effects have included renal failure, interstitial nephritis, toxic nephrosis with oliguria and anuria, crystalluria, and increases in BUN and serum creatinine.^[Ref]

Respiratory

Respiratory side effects have included cough (9.6%), pulmonary infiltrates and shortness of breath which may be due to pulmonary hypersensitivity reactions. Frequently, the pulmonary reactions have accompanied other systemic symptoms.^[Ref]

Nervous system

Nervous system side effects have included headache (4.1%), peripheral neuritis, mental depression, convulsions, ataxia, hallucinations, tinnitus, vertigo, insomnia, apathy, fatigue, muscle weakness, nervousness, and polyneuritis.^[Ref]

Metabolic

Metabolic side effects associated with sulfonamides have included diuresis and hypoglycemia. Sulfonamides are chemically similar to goitrogenic agents (i.e., diuretics and oral hypoglycemic agents).^[Ref]

Genitourinary

Genitourinary side effects have included crystalluria.^[Ref]

Endocrine

Endocrine side effects including weight gain (1 kg or greater) have been reported in 53% of patients.

Other

Other side effects have included drug fever, chills, periarteritis nodosa, and lupus erythematosus phenomenon.^[Ref]

See also:

Further information

Fansidar side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

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