Classifications: antiinfective, urinary tract; Therapeutic: antiinfective, urinary tract
Pregnancy Category: C
100 mg, 200 mg tablets; 50 mg/5 mL liquid
Antiinfective and folic acid antagonist with slow bactericidal action. Binding and interference with bacterial cell growth.
Effective against most common UTI pathogens. Most pathogens causing UTI are in normal vaginal and fecal flora.
Initial episodes of acute uncomplicated UTIs, acute otitis media in children.
Treatment and prophylaxis of chronic and recurrent UTI in both men and women; treatment in conjunction with dapsone of initial
episodes of Pneumocystis carinii pneumonia; treatment of travelers' diarrhea.
Megaloblastic anemia secondary to folate deficiency; creatinine clearance <15 mL/min, impaired kidney or liver function;
possible folate deficiency; pregnancy (category C), or in children with fragile X chromosome associated with mental retardation.
Safety in infants <2 mo has not been established.
Renal disease; mild or moderate renal impairment; lactation.
Route & Dosage
|Urinary Tract Infection
Adult: PO 100 mg b.i.d. or 200 mg once/d
Child: PO 23 mg/kg q12h x 10 d
Acute Otitis Media
Child (>6 mo): PO 10 mg/kg divided q12h x 10 d
Adult: PO 200 mg b.i.d.
- Give with 240 mL (8 oz) of fluid if not contraindicated.
- Store at 15°30° C (59°86° F) in dry, light-protected place.
Adverse Effects (≥1%) GI:
Epigastric discomfort, nausea, vomiting, glossitis, abnormal taste sensation. Hematologic:
Neutropenia, megaloblastic anemia,
methemoglobinemia, leukopenia, thrombocytopenia (rare). Skin: Rash, pruritus, exfoliative dermatitis,
photosensitivity. Body as a Whole:
Increased serum transaminases (ALT, AST), bilirubin, creatinine, BUN.
Diagnostic Test Interference
Interferes with serum methotrexate assays that use a competitive binding protein technique with a bacterial dihydrofolate reductase as the binding protein. May cause
falsely elevated creatinine values when Jaffe reaction is used.
May inhibit phenytoin
metabolism causing increased levels.
Almost completely absorbed from GI tract. Peak:
14 h. Distribution:
Widely distributed, including lung, saliva, middle ear fluid, bile, bone, CSF; crosses placenta; appears in breast milk. Metabolism:
In liver. Elimination:
80% in urine unchanged. Half-Life:
Assessment & Drug Effects
- Lab tests: Obtain C&S tests before trimethoprim therapy is initiated; therapy may be started before results are received.
Obtain periodic urine cultures, BUN, creatinine clearance, CBC, Hgb, and Hct. Follow-up cultures may be ordered at end of
treatment to verify elimination of causative organism.
- Reinforce necessity to adhere to established drug regimen. Recurrent infection after terminating prophylactic treatment of
UTI may occur even after 6 mo of therapy.
- Assess urinary pattern during treatment. Altered pattern (frequency, urgency, nocturia, retention, polyuria) may reflect
emerging drug resistance, necessitating change of drug regimen. Periodically check for bladder distention.
- Be alert for toxic effects on bone marrow, particularly in older adults, malnourished, alcoholic, pregnant, or debilitated
patients. Recognize and report signs of infection or anemia.
- Drug-induced rash, a common adverse effect, is usually maculopapular, pruritic, or morbilliform and appears 714 d
after start of therapy with daily doses of 200 mg or less.
- Watch for overdose symptoms: Nausea, vomiting, diarrhea, mental depression, confusion, facial swelling, elevated serum transaminases.
Patient & Family Education
- Take all prescribed medication; uncomplicated UTIs usually respond to treatment.
- Drink fluids liberally (20003000 mL/d, if not contraindicated) to help flush out urinary bacteria.
- Take urinary analgesic for pain and discomfort with voiding before full drug effects are experienced. Report pain and hematuria
to physician immediately.
- Do not postpone voiding even though increases in fluid intake may cause more frequent urination.
- Do not use douches or sprays during treatment periods; practice careful perineal hygiene to prevent reinfection.
- Report to physician promptly any symptoms of a hematologic disorder (fever, sore throat, pallor, purpura, ecchymosis).
- Consult physician if severe traveler's diarrhea does not respond to 35 d therapy (i.e., persistence of symptoms of
severe nausea, abdominal pain, diarrhea with mucus or blood, and dehydration).