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co-trimoxazole (sulfamethoxazole-trimethoprim)
Apo-Sulfatrim†, Apo-Sulfatrim DS†, Bactrim*, Bactrim DS, Bactrim I.V., Cotrim, Cotrim DS, Novo-Trimel†, Novo-Trimel D.S.†, Nu-Cotrimox†, Resprim‡, Roubac†, Septra*, Septra DS, Septra I.V., Septrin‡

Pregnancy Risk Category C
(contraindicated at term)

How supplied
Tablets (single-strength):
trimethoprim 80 mg and sulfamethoxazole 400 mg
Tablets (double-strength):
trimethoprim 160 mg and sulfamethoxazole 800 mg
Oral suspension:
trimethoprim 40 mg and sulfamethoxazole 200 mg/5 ml
Injection:
trimethoprim 16 mg/ml and sulfamethoxazole 80 mg/ml in 5-ml,
10-ml, 20-ml, and 30-ml vials

Action
Sulfamethoxazole inhibits formation of dihydrofolic acid from PABA; trimethoprim inhibits dihydrofolate reductase formation. Both decrease bacterial folic acid synthesis; bactericidal.

Indications & dosage
Shigellosis or urinary tract infections (UTIs) due to susceptible strains of
Escherichia coli, Proteus (indole positive or negative), Klebsiella, or Enterobacter-
Adults:
160 mg trimethoprim/800 mg sulfamethoxazole (double-strength tablet) P.O. q 12 hours for 10 to 14 days in UTIs and for 5 days in shigellosis. If indicated, I.V. infusion is given: 8 to 10 mg/kg/day (based on trimethoprim component) in two to four divided doses q 6, 8, or 12 hours for up to 14 days for severe UTIs. Maximum daily dose is 960 mg trimethoprim.
Children ages 2 months and older:
8 mg/kg/day (based on trimethoprim component) P.O., in two divided doses q 12 hours (10 days for UTIs; 5 days for shigellosis). If indicated, I.V. infusion is given: 8 to 10 mg/kg/day (based on trimethoprim component) in two to four divided doses q 6, 8, or 12 hours. Adult dose shouldn't be exceeded.
Otitis media in patients with penicillin allergy or penicillin-resistant infections
-
Children ages 2 months and older:
8 mg/kg/day (based on trimethoprim component) P.O., in two divided doses q 12 hours for 10 to 14 days.
Chronic bronchitis, upper respiratory tract infections
-
Adults:
160 mg trimethoprim/800 mg sulfamethoxazole P.O. q 12 hours for 10 to 14 days.
Traveler's diarrhea-

Adults:
160 mg trimethoprim/800 mg sulfamethoxazole P.O. b.i.d. for 3 to 5 days. Some patients may require 2 days or less of therapy.
UTIs in men with prostatitis-

Adults:
160 mg trimethoprim/800 mg sulfamethoxazole P.O. b.i.d. for 3 to 6 months.
Prophylaxis for chronic UTIs-

Adults:
40 mg trimethoprim/200 mg sulfamethoxazole (1/2 tablet) or 80 mg trimethoprim/400 mg sulfamethoxazole P.O. daily or three times weekly for 3 to 6 months.
Prophylaxis for
Pneumocystis carinii pneumonia-
Adults:
160 mg of trimethoprim/800 mg sulfamethoxazole P.O. daily.
Children ages 2 months and older:
150 mg/m2 trimethoprim/750 mg/m2 sulfamethoxazole P.O daily in two divided doses on 3 consecutive days each week.
P. carinii pneumonia-
Adults and children over age 2 months:
15 to 20 mg/kg/day (based on trimethoprim) I.V. or P.O. in three or four divided doses for 14 days.
Adjust-a-dose:
For patients with renal failure with creatinine clearance of 15 to 30 ml/minute, daily dose should be reduced by 50%. Drug isn't recommended for patients with creatinine clearance below 15 ml/minute.

Adverse reactions
CNS:
headache, mental depression, aseptic meningitis, tinnitus, apathy, seizures, hallucinations, ataxia, nervousness, fatigue, vertigo, insomnia.
CV:
thrombophlebitis.
GI:
nausea, vomiting, diarrhea, abdominal pain, anorexia, stomatitis, pancreatitis, pseudomembranous colitis.
GU: toxic nephrosis with oliguria and anuria,
crystalluria, hematuria, interstitial nephritis, increased BUN and serum creatinine levels.
Hematologic:
agranulocytosis, aplastic anemia, megaloblastic anemia, thrombocytopenia, leukopenia, hemolytic anemia.
Hepatic:
jaundice, hepatic necrosis, elevated liver function test results.
Musculoskeletal:
arthralgia, myalgia, muscle weakness.
Respiratory:
pulmonary infiltrates.
Skin:
erythema multiforme, Stevens-Johnson syndrome, generalized skin eruption, epidermal necrolysis, exfoliative dermatitis, photosensitivity, urticaria, pruritus.
Other:
hypersensitivity reactions, serum sickness, drug fever, anaphylaxis.

Interactions
Drug-drug.
Cyclosporine: may decrease cyclosporine levels and increase nephrotoxicity risk. Avoid concomitant use.
Methotrexate:
may increase methotrexate concentrations. Use together cautiously.
Oral anticoagulants:
increased anticoagulant effect. Monitor for bleeding.
Oral antidiabetics:
increased hypoglycemic effect. Monitor blood glucose levels.
Oral contraceptives:
decreased contraceptive effectiveness and increased risk of breakthrough bleeding. Suggest a nonhormonal contraceptive.
Phenytoin:
may inhibit hepatic metabolism of phenytoin. Monitor closely.
Drug-lifestyle.
Sun exposure: photosensitivity reactions may occur. Take precautions.

Effects on diagnostic tests
Trimethoprim can interfere with serum methotrexate assay as determined by the competitive binding protein technique. No interference occurs if radioimmunoassay is used.

Contraindications
Contraindicated in patients with severe renal impairment (creatinine clearance below 15 ml/minute), porphyria, megaloblastic anemia due to folate deficiency, or hypersensitivity to trimethoprim or sulfonamides. Also contraindicated in pregnant women at term, in breast-feeding women, and in infants under age 2 months.

Nursing considerations

I.V. administration

Patient teaching

Patient teaching

*Liquid contains alcohol. **May contain tartrazine.  †Canada  ‡Australia  §U.K.  OTCOver the counter
Reactions may be common, uncommon, life-threatening, or COMMON AND LIFE-THREATENING

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