Brand Names:
Bactrim, SMZ-TMP, Trimethoprim-Sulfamethoxazole, Septra


Drug Type: Antibiotic

Sulfamethoxazole-Trimethoprim

Sulfamethoxazole-Trimethoprim (SMZ-TMP) (brand name Bactrim®) is a broad-spectrum antibiotic commonly prescribed in backyard chickens. It has excellent activity against most gram-negative organisms, Staphylococci infections, pneumonia, and coccidiosis in chickens. The sulfa class of antibiotics work by depriving the bacteria of the folic acid they need without interfering with the folic acid available to the host.

The sulfa or “sulfonamide” class of antibiotics has earned a special place in history as the very first antibiotics ever developed and for the first time in human history domination over bacterial infection became readily feasible.

Egg Withdrawal Period: Sulfamethoxazole-Trimethoprim should not be given to poultry producing eggs intended for human consumption in any country, due to the lack of studies on the duration of residues in the eggs of treated hens. Australia recommends 10-day withdrawal period for eggs.

Caution: Sulfamethoxazole-Trimethoprim can precipitate in urine forming crystals or even stones, leading to kidney damage and gout. This is typically a problem with prolonged use or acidified urine. Sulfa drugs should not be given to birds with liver or kidney problems.
  • 360-400 mg/L drinking water q24h (Spears)
  • 100 mg/kg PO q12h (Spears)
Available as 125 mg, 250 mg, or 500 mg tablets and oral suspension.
  • Acetylsalicylic acid: The risk or severity of hypoglycemia can be increased when Acetylsalicylic acid is combined with Sulfamethoxazole.
  • Albendazole: The metabolism of Albendazole can be decreased when combined with Sulfamethoxazole.
  • Bismuth subsalicylate: Bismuth subsalicylate may increase the hypoglycemic activities of Sulfamethoxazole.
  • Carprofen: The risk or severity of hyperkalemia can be increased when Carprofen is combined with Sulfamethoxazole.
  • Choline salicylate: Choline salicylate may increase the hypoglycemic activities of Sulfamethoxazole.
  • Dexamethasone acetate: The risk or severity of hyperglycemia can be increased when Dexamethasone acetate is combined with Sulfamethoxazole.
  • Enalapril: The risk or severity of myopathy, rhabdomyolysis, and myoglobinuria can be increased when Enalapril is combined with Sulfamethoxazole.
  • Fish oil: The risk or severity of hyperkalemia can be increased when Sulfamethoxazole is combined with Fish oil.
  • Furosemide: The therapeutic efficacy of Sulfamethoxazole can be decreased when used in combination with Furosemide.
  • Ginkgo biloba: The metabolism of Sulfamethoxazole can be decreased when combined with Ginkgo biloba.
  • Ivermectin: The risk or severity of myopathy, rhabdomyolysis, and myoglobinuria can be increased when Ivermectin is combined with Sulfamethoxazole.
  • Magnesium sulfate:The risk or severity of hypoglycemia can be increased when Magnesium sulfate is combined with Sulfamethoxazole.
  • Methylprednisolone aceponate: The risk or severity of hyperglycemia can be increased when Methylprednisolone aceponate is combined with Sulfamethoxazole.
  • Miconazole:The metabolism of Sulfamethoxazole can be decreased when combined with Miconazole.
  • Niacin: The therapeutic efficacy of Sulfamethoxazole can be decreased when used in combination with Niacin.
  • Piperazine: The therapeutic efficacy of Sulfamethoxazole can be decreased when used in combination with Piperazine.
  • Prednisolone acetate: The risk or severity of hyperglycemia can be increased when Prednisolone acetate is combined with Sulfamethoxazole
  • St. John's Wort: The therapeutic efficacy of Sulfamethoxazole can be decreased when used in combination with St. John's Wort.
  • Sulfadiazine: The risk or severity of hypoglycemia can be increased when Sulfadiazine is combined with Sulfamethoxazole.
  • Terbinafine: The risk or severity of myopathy, rhabdomyolysis, and myoglobinuria can be increased when Terbinafine is combined with Sulfamethoxazole.