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Bactrim

Clinical Effects:

TRIMETHOPRIM
  • USES: Trimethoprim is used to treat initial episodes of uncomplicated urinary tract infections due to susceptible strains of E coli, Proteus mirabilis, Klebsiella pneumoniae, Enterobacter species, and coagulase-negative Staphylococcus species, including S. saprophyticus. It is also indicated in the treatment of acute otitis media caused by susceptible strains of Streptococcus pneumoniae and Haemophilus influenzae. PHARMACOLOGY: Trimethoprim is a synthetic antibacterial agent that binds and reversibly blocks dihydrofolate reductase to inhibit the formation of tetrahydrofolic acid from dihydrofolic acid, a substance needed for bacterial growth. EPIDEMIOLOGY: Exposure may occur. However, significant toxicity is uncommon. OVERDOSE: ACUTE TOXICITY: Following an overdose of 1 g or more of trimethoprim, effects may include: nausea, vomiting, dizziness, headaches, depressed consciousness, confusion, and bone marrow suppression. Jaundice and mild elevation of SGOT were reported in one case of trimethoprim overdose. ADVERSE EFFECTS: COMMON: Rash and pruritus. Other effects have included: nausea and vomiting, glossitis, epigastric distress, hyperkalemia, hyponatremia, thrombocytopenia, leukopenia, neutropenia, megaloblastic anemia, and methemoglobinemia. RARE: Exfoliative dermatitis, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, anaphylaxis, cholestatic jaundice and aseptic meningitis have occurred. CHRONIC: High dose therapy and/or extended use may cause bone marrow depression manifested as thrombocytopenia, leukopenia, and megaloblastic anemia. LABORATORY: Increases in BUN and serum creatinine levels have been reported in patients using trimethoprim. OPHTHALMIC PREPARATIONS: Significant toxicity is NOT expected to occur following acute ingestion or topical application of ophthalmic preparations containing trimethoprim. Local irritation consisting of redness, burning, stinging, and/or itching have been reported following the use of trimethoprim/polymyxin B sulfate ophthalmic solution. For information on trimethoprim and sulfamethoxazole combination, please refer to “TRIMETHOPRIM-SULFAMETHOXAZOLE” management.
TRIMETHOPRIM-SULFAMETHOXAZOLE
  • USES: Trimethoprim and sulfamethoxazole is a synthetic antibacterial combination product. It is used in a wide variety of infections due to susceptible organisms, in particular those of the urinary, respiratory, and gastrointestinal tracts. PHARMACOLOGY: The combination of trimethoprim-sulfamethoxazole block 2 steps in the biosynthesis of nucleic acids and proteins essential to the growth of many bacteria. Trimethoprim blocks the production of tetrahydrofolic acid from dihydrofolic acid by binding to and reversibly inhibiting the required enzyme, dihydrofolate reductase. Sulfamethoxazole is able to inhibit the bacterial synthesis of dihydrofolic acid by competing with para-aminnobezoic acid (PABA). EPIDEMIOLOGY: Exposure is common, but severe toxicity is unlikely to occur. OVERDOSE: TOXICITY: TRIMETHOPRIM: Nausea and vomiting, dizziness, headache, mental depression, confusion, and bone marrow depression can occur with a trimethoprim overdose. SULFONAMIDES: Anorexia, colic, nausea and vomiting, dizziness, headache, drowsiness, unconsciousness, pyrexia, hematuria, crystalluria, renal insufficiency, blood dyscrasias and jaundice can occur with a sulfonamide overdose. ADVERSE EFFECTS: COMMON: Nausea and vomiting, anorexia and allergic skin reactions (e.g., rash and urticaria) are the most common adverse events. INFREQUENT: Severe reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, other blood dyscrasias have occurred. RARE: Hypersensitivity of the respiratory tract has resulted in death in some cases. CHRONIC USE: Ongoing high dose use and/or extended periods of use may result in bone marrow depression and include thrombocytopenia, leukopenia, and/or megaloblastic anemia.

Range of Toxicity:

TRIMETHOPRIM
  • TOXICITY: ACUTE EXPOSURE: Following an overdose of 1 g or more of trimethoprim, effects may include: nausea, vomiting, dizziness, headaches, depressed consciousness, confusion, and bone marrow suppression. CHRONIC EXPOSURE: Use of high doses and/or for extended periods of time may cause bone marrow depression (ie, thrombocytopenia, leukopenia, and/or megaloblastic anemia). THERAPEUTIC DOSE: TRIMETHOPRIM ALONE: ADULT: TABLET: 100 mg orally every 12 hours for 10 days or 200 mg once daily for 10 days for urinary tract infection. ORAL SOLUTION: 100 mg orally every 12 hours for 10 days or 200 mg once daily for 10 days for uncomplicated urinary tract infection. PEDIATRIC: TABLET: Safety and effectiveness have not been established in children under 12 years. ORAL SOLUTION: CHILDREN 5 MONTHS OR YOUNGER: Safety and effectiveness have not been established. CHILDREN 6 MONTHS TO 17 YEARS: 5 mg/kg every 12 hours for 10 days for the treatment of otitis media. OPHTHALMIC SOLUTION: TRIMETHOPRIM/POLYMYXIN B SULFATE: ADULT: Instill 1 drop in the affected eye(s) every 3 hours (maximum of 6 doses/day) for 7 to 10 days. PEDIATRIC: CHILDREN 2 MONTHS TO 17 YEARS: Instill 1 drop in the affected eye(s) every 3 hours for 7 to 10 days; MAX: 6 doses/day. CHILDREN 1 MONTH OR YOUNGER: Safety and effectiveness have not been established.
TRIMETHOPRIM-SULFAMETHOXAZOLE
  • TOXICITY: A toxic dose has not been established for trimethoprim and sulfamethoxazole. Overdoses with toxic effects have occurred following 1 gram or more of trimethoprim. Ingestion of 8 g of sulfamethoxazole and 1.6 g of trimethoprim (20 tablets) resulted in renal insufficiency in an elderly man. An iatrogenic overdose of intravenous trimethoprim/sulfamethoxazole (20 mg/kg/dose of trimethoprim) every 6 hours for 11 doses resulted in agitation, disorientation, psychosis and a tonic-clonic seizure. THERAPEUTIC DOSE: ADULT: Varies by indication. Range: Two regular strength tablets every 12 hours; 20 mL suspension every 12 hours or 1 double-strength tablet every 12 hours for 10 to 14 days. CHILD: OTITIS MEDIA or URINARY TRACT INFECTION: 8 mg/kg trimethoprim and 40 mg/kg sulfamethoxazole every 24 hours given in divided doses every 12 hours for 10 days.

Treatment:

TRIMETHOPRIM
  • Support: MANAGEMENT OF MILD TO MODERATE TOXICITY: Treatment is symptomatic and supportive. Gastrointestinal symptoms (ie, nausea, vomiting) are likely to occur and mild symptoms can be managed with oral fluids; IV fluids and electrolyte replacements may be needed if symptoms persist or become significant. MANAGEMENT OF SEVERE TOXICITY: Treatment is symptomatic and supportive. Treat gastrointestinal symptoms as needed. Obtain electrolytes, if symptoms persist. Monitor liver enzymes and renal function following a significant exposure. Drowsiness, depression, and confusion can develop. Monitor CNS function. RARE: In rare cases, severe bone marrow depression including thrombocytopenia, leukopenia, megaloblastic anemia and methemoglobinemia may develop. Obtain a baseline CBC with differential in patients with a significant acute and/or chronic exposure. Anaphylaxis has been reported rarely with trimethoprim therapy. Seizures have been reported rarely following intravenous exposure. Initially treat seizures with a benzodiazepines (diazepam or lorazepam). Consider phenobarbital or propofol if seizures recur or persist.
  • Decontamination: PREHOSPITAL: Gastrointestinal decontamination is not indicated if the patient has developed nausea and vomiting and/or the airway cannot be protected. Consider activated charcoal following a significant, recent exposure. HOSPITAL: Consider activated charcoal following a recent significant exposure, or if significant coingestants are involved and the airway can be protected.
  • Antidote: There is no known antidote.
  • Airway management: Airway support is unlikely to be necessary following a mild to moderate exposure. There are rare reports of anaphylaxis following trimethoprim use. Ensure adequate ventilation and perform endotracheal intubation early in patients with severe allergic reactions.
  • Myelosuppression: Patients receiving chronic therapy may be more likely to develop myelosuppression. Monitor CBC with differential as indicated. Administer leucovorin/folinic acid at 5 to 15 mg orally daily to minimize hematologic toxicity. For severe neutropenia, administer colony stimulating factor. Filgrastim 5 mcg/kg/day subQ or IV over 15 to 30 minutes. Sargramostim 250 mcg/meter(2)/day IV over 4 hours. Transfusion of platelets and/or packed red cells may be needed in patients with severe thrombocytopenia, anemia or hemorrhage.
  • Monitoring of patient: Monitor fluid and electrolyte status including sodium and potassium after acute overdose and in patients with severe vomiting. Monitor serial CBC with differential and platelet count in symptomatic patients. Monitor hepatic enzymes and renal function after a significant overdose.
  • Enhanced elimination procedure: Hemodialysis is only moderately effective in elimination of trimethoprim. Trimethoprim is 44% bound to plasma proteins. Peritoneal dialysis is not thought to be effective following overdose.
  • Patient disposition: HOME CRITERIA: An asymptomatic child taking an inadvertent 1 to 2 tablets can likely be monitored at home, or an asymptomatic adult taking an inadvertent extra dose can be safely managed at home. OBSERVATION CRITERIA: Patients with a deliberate self-harm ingestion should be evaluated in a healthcare facility and monitored until symptoms resolve. Obtain a baseline CBC with differential, electrolytes and renal function following a significant exposure. Patients may be discharged to home once symptoms have resolved and laboratory studies are within normal limits. ADMISSION CRITERIA: Patients with severe blood dyscrasias, severe or persistent CNS depression, or anaphylactic symptoms should be admitted. CONSULT CRITERIA: Contact a medical toxicologist or regional poison center for assistance in managing patients with severe toxicity or in whom the diagnosis is unclear. Patients with a deliberate self-harm ingestion should be evaluated by a mental health specialist.
TRIMETHOPRIM-SULFAMETHOXAZOLE
  • Support: MANAGEMENT OF MILD TO MODERATE TOXICITY: Treatment is symptomatic and supportive. Gastrointestinal symptoms (ie, nausea, vomiting, diarrhea) are likely to occur and mild symptoms can be managed with oral fluids; IV fluids and antiemetics may be needed if symptoms persist or become significant. Monitor urine output. MANAGEMENT OF SEVERE TOXICITY: Treatment is symptomatic and supportive. Treat gastrointestinal symptoms as needed. Obtain electrolytes, if symptoms persist. Monitor CNS function. Drowsiness, depression, and confusion can develop. Hypoglycemia may develop in patients receiving high doses; monitor glucose as indicated. Severe toxicity is not anticipated. RARE: In rare cases, severe bone marrow depression including thrombocytopenia, leukopenia, and/or megaloblastic anemia may develop. Severe even fatal hypersensitivity reactions have occurred with therapeutic use and may begin as a skin rash and can progress to severe reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, hepatic necrosis, and severe blood dyscrasias. Monitor CBC with differential and hepatic and renal function.
  • Decontamination: PREHOSPITAL: Significant toxicity is unlikely after acute ingestion and gastrointestinal decontamination is generally unnecessary. Decontamination should be considered in patients with suspected coingestants or a large ingestion. HOSPITAL: Administer activated charcoal in a patient with a significant ingestion or suspected coingestants that is alert and able to protect their airway or the airway is supported.
  • Airway management: Airway management is unlikely to be necessary. In the event of a hypersensitivity reaction, airway support and management may be necessary.
  • Antidote: There is no known antidote.
  • Monitoring of patient: Monitor fluid and electrolyte status including sodium and potassium after acute overdose and in patients with severe vomiting. Monitor serial CBC with differential and platelet count in symptomatic patients. Monitor hepatic and renal function after a significant overdose.
  • Enhanced elimination procedure: Techniques to enhance elimination are not likely to be necessary as severe toxicity is rare and patients usually recover with supportive care. Hemodialysis is only moderately effective in eliminating trimethoprim and sulfamethoxazole.
  • Patient disposition: HOME CRITERIA: An asymptomatic child taking an inadvertent 1 to 2 tablets can likely be monitored at home, or an asymptomatic adult taking an inadvertent extra dose can be safely managed at home. OBSERVATION CRITERIA: Patients with a deliberate self-harm ingestion should be evaluated in a healthcare facility and monitored until symptoms resolve. Obtain a baseline CBC with differential, electrolytes and renal function following a significant exposure. Patients may be discharged to home once symptoms have resolved and laboratory studies are within normal limits. ADMISSION CRITERIA: Patients experiencing severe or persistent anaphylactic symptoms or who develop evidence of blood dyscrasias should be admitted for further monitoring and treatment as indicated. CONSULT CRITERIA: Contact a medical toxicologist or regional poison center for assistance in managing patients with severe toxicity or in whom the diagnosis is unclear. Patients with a deliberate self-harm ingestion should be evaluated by a mental health specialist.
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