Acute exacerbations of chronic bronchitis due to susceptible strains of Streptococcus pneumoniae or Haemophilus influenzaeDocumented Pneumocystis jiroveci pneumonia (PCP); also, prophylaxis against PCP in individuals who are immunosuppressedEnteritis caused by susceptible strains of Shigella flexneri and S sonneiAlternatively, 8-10 mg TMP/kg/day IV divided q6-12hr for up to 5 days Traveler's diarrhea due to susceptible strains of enterotoxigenic Escherichia coliUTIs caused by susceptible strains of Escherichia coli, Klebsiella species, Enterobacter species, Morganella morganii, Proteus mirabilis, and Proteus vulgarisPyelonephritis: 1 DS tab or 2 regular-strength tabs PO q12hr x 14 daysProstatitis: 1 DS tab or 2 regular-strength tabs PO q12hr x 14 days or 2-3 months if chronic infectionA 3 to 5 day course may be used for acute, uncomplicated cystitisProphylaxis (off-label): Various regimens exist; may use regular-strength tablet once/twice per week1 DS tab or 1 regular-strength tab PO qDay or q12hr for up to 18 weeksAcute otitis media in pediatric patients due to susceptible strains of Streptococcus pneumoniae or Haemophilus influenzae>2 months: 6-10 mg TMP/kg/day PO divided q12hr for 10 days 8-12 mg TMP/kg/day PO divided q12hr for 5-10 days; add beta-lactam antibiotic to regimen if beta-hemolytic Streptococcus spp also suspected QT prolongation resulting in ventricular tachycardia and torsade de pointesRisk associated with concurrent use of leucovorin forDrug reaction with eosinophilia and systemic symptoms (DRESS)CrCl <15 mL/min when renal function status cannot be monitoredDocumented megaloblastic or folate deficiency anemiaContraindicated in pregnant patients at term and in nursing mothers, because sulfonamides, which pass the placenta and are excreted in the milk, may cause kernicterusHistory of drug-induced immune thrombocytopenia with use of trimethoprim and/or sulfonamidesTreatment with recommended doses may cause hyperkalemia when trimethoprim is administered to patients with underlying disorders of potassium metabolism, with renal insufficiency, or if drugs known to induce hyperkalemia are given concomitantly; close monitoring of serum potassium recommendedSevere and symptomatic hyponatremia can occur in patients receiving sulfamethoxazole/trimethoprim, particularly for treatment of Fatalities associated with the administration of sulfonamides, although rare, have occurred due to severe reactions, including severe cutaneous adverse reactions (SCARs), including Stevens-Johnson Syndrome, toxic epidermal necrolysis, drug reaction with eosinophilia and systemic symptoms (DRESS), acute generalized exanthematous pustulosis (AGEP) and acute febrile neutrophilic dermatosis (AFND), fulminant hepatic necrosis, agranulocytosis, aplastic anemia and other blood dyscrasias; clinical signs, such as rash, sore throat, fever, arthralgia, pallor, purpura or jaundice may be early indications of serious reactionsCaution when used in elderly individuals; risk of bone marrow suppressionPCP prophylaxis with AIDS: Rash, fever, leukopenia, and elevated transaminase values reported; hyperkalemia and hyponatremia also appear to be increasedSevere cases (including fatalities) of immune-mediated thrombocytopenia reported; monitor patients for hematologic toxicitySulfonamides should not be used to treat group A beta-hemolytic streptococcal infections; they will not eradicate streptococcus or prevent rheumatic feverCoadministration with leucovorin for the treatment of HIV-positive patients with PCP resulted in treatment failure and excess mortality in a randomized, placebo-controlled trial; avoid coadministrationDevelopment of drug-resistant bacteria may occur when prescribed in absence of strongly suspected bacterial infection or prophylactic indicationProlonged use may result in fungal or bacterial superinfectionCaution with impaired renal or hepatic function, patients with possible folate deficiency (eg, the elderly, chronic alcoholics, patients receiving anticonvulsant therapy, patients with malabsorption syndrome, and patients in malnutrition states), and patients with severe allergies or bronchial asthmaHemolysis may occur if administered to patients with G6PD deficiencyHypoglycemia (rare) reported in nondiabetic patients; patients with renal dysfunction, liver disease, or malnutrition or those receiving high doses at particular riskCaution with porphyria or thyroid dysfunction; sulfonamides can precipitate porphyria crisis and hypothyroidism; avoid use in patients with porphyria or thyroid dysfunctionComplete blood counts should be done frequently in patients receiving therapy; discontinue therapy if a significant reduction in count of any formed blood element is noted’ perform urinalyses with careful microscopic examination and renal function tests during therapy, particularly for those patients with impaired renal functionWhen administered at high doses as for the treatment of P. jirovecii pneumonia, monitor for total daily intake of propylene glycol from all sources and for acid-base disturbances; discontinue therapy if propylene glycol toxicity suspectedTreatment failure and excess mortality were observed when trimethoprim-sulfamethoxazole was used concomitantly with leucovorin for treatment of HIV positive patients with Pneumocystis jirovecii pneumonia; co-administration of trimethoprim-sulfamethoxazole and leucovorin during treatment of During treatment, adequate fluid intake and urinary output should be ensured to prevent crystalluria; patients who are “slow acetylators” may be more prone to idiosyncratic reactions to sulfonamidesTherapy may cause fetal harm if administered to pregnant woman; some epidemiologic studies suggest that exposure to drug during pregnancy may be associated with increased risk of congenital malformations, particularly neural tube defects, cardiovascular abnormalities, urinary tract defects, oral clefts, and club footUrinary tract infection in pregnancy is associated with adverse perinatal outcomes such as preterm birth, low birth weight, and pre-eclampsia, and increased mortality to pregnant womanP.

Controlled studies in pregnant women show no evidence of fetal risk.Blocks 2 consecutive steps in the biosynthesis of nucleic acids and proteins essential to many bacteriaTrimethoprim: Inhibits dihydrofolate reductase, thereby blocking production of tetrahydrofolic acid from dihydrofolic acidSulfamethoxazole: Inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acidY-site: Cisatracurium (incompatible at 2 mg/mL cisatra; may be compatible at much lower concs), fluconazole, foscarnet (may be compatible at very low TMP/SMX concs), midazolam, vinorelbineInjection vehicle contains benzyl alcohol and sodium metabisulfiteMaintain adequate fluid intake to prevent crystalluriaAdding plans allows you to compare formulary status to other drugs in the same class.To view formulary information first create a list of plans.