Sulfamethoxazole-trimethoprim

Information about Sulfamethoxazole-trimethoprim

Sulfamethoxazole with trimethoprim is a fixed antibiotic combination that is widely used for mild-to-moderate bacterial infections and as prophylaxis against opportunistic infections.

Liver toxicity of Sulfamethoxazole-trimethoprim

Like other sulfonamide-containing medications, this combination has been linked to rare instances of clinically apparent acute liver injury.

Mechanism of action of Sulfamethoxazole-trimethoprim

Trimethoprim-sulfamethoxazole (TMP-SMZ) is a combination of a sulfonamide antibiotic and a methoprim. This combination is widely used for therapy of infections due to susceptible bacteria as well as prevention of opportunistic infections with Pneumocystis jiroveci (formerly carinii) in immune deficient individuals. The two agents are synergistic in inhibition of folate synthesis – the sulfamethoxazole (sul" fa meth ox' a zole) inhibiting production of dihydrofolate from para-aminobenzoic acid, and the trimethoprim (trye meth' oh prim) inhibiting the next step in the pathway from dihydrofolate to tetrahydrofolate.

FDA approval information for Sulfamethoxazole-trimethoprim

TMP-SMZ was approved for use as a combination antibiotic in the United States in 1973 and is still in wide use, more than 8 million prescriptions being filled yearly. TMP-SMZ is recommended for use in adults and children for urinary tract infections, bronchitis, sinusitis and otitis media and for prophylaxis against opportunistic infections due to parasites and pneumocystitis jiroveci.

Dosage and administration for Sulfamethoxazole-trimethoprim

TMP-SMZ is available in multiple generic and trade formulations in tablets containing 80 or 160 mg of trimethoprim and 200, 400 or 800 mg of sulfamethoxazole. Trade names include Bactrim, Cotrim, Septra and Sulfatrim.

Trimethoprim is also available separately and is used as an antibiotic for uncomplicated urinary tract infections. Trimethoprim is a synthetic antifolate that acts on a late step in the pathway of folate synthesis. Trimethprim has activity against many aerobic gram-negative organisms such as Escherichia coli, Kiebsiella pneumoniae, Proteus mirabilis and Enterobacter species. Resistance is common. Trimethoprim was approved for use in the United States in 1980, but is used much less frequently that TMP-SMZ. Trimethoprim is available in several generic forms in tablets of 100 mg and the usual oral adult dose is 100 mg twice daily for 10 days.

Side effects of Sulfamethoxazole-trimethoprim

Trimethoprim is generally well tolerated; side effects can include nausea, abdominal upset, rash and pruritus.

• Dailymed label info on Sulfamethoxazole-trimethoprim
• FDA Sulfamethoxazole-trimethoprim

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