Co-Trimoxazole

Generic name: Co-trimoxazole (trimethoprim sulfamethoxazole)

Brand name: Septra (GSK), Bactrim (Roche)

Drug class: Sulfonamide antibiotic

Actions

Trimethoprim inhibits the synthesis of nucleic acids and proteins in susceptible bacteria; the bacterial enzyme involved in this reaction is more readily inhibited than the mammalian enzyme.

Sulfamethoxazole acts as a false-substrate inhibitor of dihydropteroate synthetase. Sulfonamides such as sulfamethoxazole are analogues of p-aminobenzoic acid (PABA) and are competitive inhibitors of the enzyme; inhibiting the production of dihydropteroic acid.

Indications

Uncomplicated UTIs caused by susceptible strains of Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae, Enterobacter species, and coagulase-negative Staphylococcus species, including S. Saprophyticus.
Treatment of acute otitis media due to susceptible strains of S. Pneumoniae and Haemophilus influenzae in children.
Unlabeled uses: With dapsone for treatment of initial episodes of Pneumocystis jiroveci (carinii) pneumonia in patients who can tolerate co-trimoxazole; treatment and prevention of traveller’s diarrhea.

Contraindications

Contraindicated with allergy to trimethoprim and sulfamethoxazole, pregnancy (teratogenic in pre-clinical studies), megaloblastic anemia due to folate deficiency.
Use cautiously with hepatic or renal impairment, lactation.

Available forms

Tablets – 100, 200 mg

Side Effects

Rash
Pruritus
Fever
Epigastric distress
Nausea
Vomiting

Nursing considerations

Perform culture and sensitivity tests before beginning drug therapy.
Protect the 200mg tablets from exposure to light.
Arrange for regular, periodic blood counts during therapy.
Discontinue drug and consult with physician if any significant reduction in any formed blood element occurs.