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Gantanol Side Effects

Generic name: sulfamethoxazole

Note: This document contains side effect information about sulfamethoxazole. Some of the dosage forms listed on this page may not apply to the brand name Gantanol.

Applies to sulfamethoxazole: compounding powder, oral tablet


Hypotension, pulmonary edema, and elevated serum transaminases have been reported following administration of trimethoprim-sulfamethoxazole (the active ingredient contained in Gantanol) to patients with HIV infection. Cholestatic jaundice, thought to be due to hypersensitivity, has been reported with sulfamethoxazole alone.

The use of sulfonamide antibiotics, including sulfamethoxazole, 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]

Hypersensitivity reactions most commonly present as an urticarial rash. Rare cases of anaphylaxis, toxic epidermal necrolysis, and Stevens-Johnson syndrome have been reported. Hypersensitivity reactions may be more likely in patients with the Acquired Immunodeficiency Syndrome (AIDS).[Ref]

Nervous system

Rare cases of aseptic meningitis associated with trimethoprim-sulfamethoxazole (the active ingredient contained in Gantanol) have been reported. In addition, reversible tremors, ataxia, catatonia, and seizures have been observed in patients with AIDS.

A single case of acute psychosis has been associated with the routine use of oral trimethoprim-sulfamethoxazole (TMP-SMX). This reaction is believed to be due to the SMX component of the drug.[Ref]

Neurologic side effects are uncommon and include headache, depression, and hallucinations.[Ref]


Methemoglobinemia induced by sulfamethoxazole (the active ingredient contained in Gantanol) has been reported.

There is in vitro evidence for a sulfamethoxazole-associated antiplatelet antibody. Serologic studies (flow cytometry) on a man with profound and symptomatic thrombocytopenia, associated with trimethoprim-sulfamethoxazole (TMP-SMX), revealed significant SMX-dependent platelet-reactive antibody. These findings are consistent with a diagnosis of SMX-induced immune thrombocytopenia.[Ref]

Hematologic side effects are unusual and include thrombocytopenia, leukopenia, agranulocytosis, and hemolytic, megaloblastic, and aplastic anemias.[Ref]


Sulfamethoxazole (the active ingredient contained in Gantanol) may induce sulfa crystal precipitation in renal tubules. Rare cases of interstitial nephritis and tubular necrosis have been reported and are thought to be due to a hypersensitivity mechanism.[Ref]

Renal side effects occur occasionally, probably due to sulfa crystalluria. These side effects may be less likely with adequate hydration. Frequent monitoring of serum creatinine and urinalysis is recommended during sulfamethoxazole therapy in patients with renal insufficiency. Acute interstitial nephritis has rarely been observed with trimethoprim-sulfamethoxazole, but may be due to the trimethoprim component.[Ref]


Gastrointestinal side effects, such as nausea and vomiting, are usually mild. Diarrhea and hepatitis are infrequent.[Ref]

Rare cases of pancreatitis associated with sulfamethoxazole have been reported.[Ref]


Cholestatic hepatitis associated with sulfamethoxazole (the active ingredient contained in Gantanol) therapy may present with other signs of hypersensitivity, such as rash, fever, and eosinophilia.[Ref]

Hepatic side effects are rare but can be serious. Isolated cases of jaundice due to cholestasis have been reported. Fulminant hepatic failure has occurred in a few patients treated with trimethoprim-sulfamethoxazole and is likely due to the sulfamethoxazole component. Frequent monitoring of liver function tests during sulfamethoxazole therapy is recommended in patients with liver dysfunction.[Ref]


Sulfamethoxazole, like other sulfonamides, may induce hypoglycemia by stimulating pancreatic islet cells to secrete insulin. A single case of hypoglycemic stupor associated with trimethoprim-sulfamethoxazole (the active ingredient contained in Gantanol) has been reported. This patient also had AIDS, may have had another viral infection, and was on other medications.[Ref]

Endocrine side effects including hypoglycemia have been reported rarely.[Ref]

Frequently asked questions


1. Gibson J "Recurrent trimethoprim-associated fixed skin eruption." Br Med J 284 (1982): 1529-30

2. Fernandez-Rivas M, Rebolleda G, De La Hoz B, Losada E "Conjunctivitis after oral administration of sulfamethoxazole." Ann Allergy 66 (1991): 272

3. Johnson M, Goodwin D, Shands J "Trimethoprim-sulfamethoxazole anaphylactoid reactions in patients with AIDS: case reports and literature review." Pharmacotherapy 10 (1990): 413-16

4. Horak J, Mertl L, Hrabal P "Severe liver injuries due to sulfamethoxazole-trimethoprim and sulfamethoxydiazine." Hepatogastroenterology 31 (1984): 199-200

5. Roujeau JC, Kelly JP, Naldi L, et al. "Medication use and the risk of Stevens-Johnson syndrome or toxic epidermal necrolysis." N Engl J Med 333 (1995): 1600-7

6. Hofer T, Becker EW, Weigand K, Berg PA "Demonstration of sensititzed lymphocytes to trimethoprim/sulfamethoxazole and ofloxacin in a patient with cholestatic hepatitis." J Hepatol 15 (1992): 262-3

7. Steinbrecher U, Mishkin S "Sulfamethoxazole-induced hepatic injury." Dig Dis Sci 26 (1981): 756-9

8. Gutt L, Feder J, Feder R, Grammer LC, Shaughnessy MA, Patterson R "Corneal ring formation after exposure to sulfamethoxazole." Arch Ophthalmol 106 (1988): 726-7

9. Schattner A, Rimon E, Green L, Coslovsky R, Bentwich Z "Hypoglycemia induced by co-trimoxazole in AIDS." BMJ 297 (1988): 742

10. Smith E, Light J, Filo R, Yum M "Interstitial nephritis caused by trimethoprim-sulfamethoxazole in renal transplant recipients." JAMA 244 (1980): 360-1

11. Ulstad D, Ampel N, Shon B, Galgiani JN, Cutcher AB "Reaction after re-exposure to trimethoprim-sulfamethoxazole." Chest 95 (1989): 937-8

12. Kelly W, Dooley D, Lattuada C, Smith C "A severe, unusual reaction to trimethoprim-sulfamethoxazole in patients infected with human immunodeficiency virus." Clin Infect Dis 14 (1992): 1034-9

13. Marinac JS, Stanford JF "A severe hypersensitive reaction to trimethoprim-sulfamethoxazole in a patient infected with human immunodeficiency virus." Clin Infect Dis 16 (1993): 178-9

14. Rudra T, Webb D, Evans A "Acute tubular necrosis following co-trimoxazole therapy." Nephron 53 (1989): 85-6

15. Holdcroft C, Ellison R "Trimethoprim-sulfamethoxazole reaction simulating pneumocystis carinii pneumonia." AIDS 5 (1991): 1029-42

16. Ransohoff D, Jacobs G "Terminal hepatic failure following a small dose of sulfamethoxazole-trimethoprim." Gastroenterology 80 (1981): 816-9

17. Whittington R "Toxic epidermal necrolysis and co-trimoxazole." Lancet 2 (1989): 574

18. Fischl M, Dickinson G, LaVoie L "Safety and efficacy of sulfamethoxazole and trimethoprim chemoprophylaxis for pneumocystis carinii pneumonia in AIDS." JAMA 259 (1988): 1185-9

19. Stevenson D, Christie D, Haas J "Hepatic injury in a child caused by trimethoprim-sulfamethoxazole." Pediatrics 61 (1978): 864-6

20. Heer M, Altorfer J, Burger H, Walti M "Bullous esophageal lesions due to co-trimoxazole: an immune-mediated process?" Gastroenterology 88 (1985): 1954-7

21. Basista MP "Randomized study to evaluate efficacy and safety of ofloxacin vs trimethoprim and sulfamethoxazole in treatment of uncomplicated urinary tract infection." Urology 37 (1991): 21-7

22. Gregor JC, Zilli CA, Gotlib IH "Acute psychosis associated with oral trimethoprim-sulfamethoxazole therapy." Can J Psychiatry 38 (1993): 56-8

23. Borucki MJ, Matzke DS, Pollard R "Tremor induced by trimethoprim-sulfamethoxazole in patients with the acquired immunodeficiency syndrome (AIDS)." Ann Intern Med 109 (1988): 77-8

24. Joffe A, Farley J, Linden D, Goldsand G "Trimethoprim-sulfamethoxazole-associated aseptic meningitis: case reports and review of the literature." Am J Med 87 (1989): 332-8

25. Liu L, Seward S, Crumpacker C "Intravenous trimethoprim-sulfamethoxazole and ataxia." Ann Intern Med 104 (1986): 448

26. McCue J, Zandt J "Acute psychoses associated with the use of ciprofloxacin and trimethoprim-sulfamethoxazole." Am J Med 90 (1991): 528-9

27. Bovino J, Marcus D "The mechanism of transient myopia induced by sulfonamide therapy." Am J Ophthalmol 94 (1982): 99-102

28. Betkowski AS, Lubin A "Sulfamethoxazole-related antiplatelet antibody." Blood 82 (1993): 1683

29. Chan M, Beale D, Moorhead J "Acute megaloblastosis due to cotrimoxazole." Br J Clin Pract 34 (1980): 87-8

30. Barak S, Shaked Y, Bar A, Samra Y "Drug-induced post-surgical hemorrhage resulting from trimethoprim-sulphamethoxazole." Int J Oral Maxillofac Surg 18 (1989): 206-7

31. Damergis J, Stoker J, Abadie J "Methemoglobinemia after sulfamethoxazole and trimethoprim therapy." JAMA 249 (1983): 590-1

32. Cryst C, Hammar S "Acute granulomatous interstitial nephritis due to co-trimoxazole." Am J Nephrol 8 (1988): 483-8

33. Kowdley K, Keeffe E, Fawaz K "Prolonged cholestasis due to trimethoprim-sulfamethoxazole." Gastroenterology 102 (1992): 2148-50

34. Sugarman B "Trimethoprim-sulfamethoxazole, pseudomembranous colitis, and spinal cord injury." South Med J 78 (1985): 711-3

35. Alberti-Flor JJ, Hernandez ME, Ferrer JP, Howell S, Jeffers L "Fulminant liver failure and pancreatitis associated with the use of sulfamethoxazole-trimethoprim." Am J Gastroenterol 84 (1989): 1577-9

36. Simma B, Meister B, Deutsch J, Sperl W, Fend F, Ofner D, Margreiter R, Vogel W "Fulminant hepatic failure in a child as a potential adverse effect of trimethoprim-sulphamethoxazole." Eur J Pediatr 154 (1995): 530-3

37. Johnson JA, Kappel JE, Sharif MN "Hypoglycemia secondary to trimethoprim/sulfamethoxazole administration in a renal transplant patient." Ann Pharmacother 27 (1993): 304-6

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.