Acute Exacerbations of Chronic Bronchitis in Adults: For the treatment of acute exacerbations of chronic bronchitis due to susceptible strains of Streptococcus pneumoniae or Haemophilus influenzae when in the judgment of the physician BACTRIM offers some advantage over the use of a single antimicrobial agent.
Shigellosis: For the treatment of enteritis caused by susceptible strains of Shigella flexneri and Shigella sonnei when antibacterial therapy is indicated.
Pneumocystis Carinii Pneumonia: For the treatment of documented Pneumocystis carinii pneumonia and for prophylaxis against Pneumocystis carinii pneumonia in individuals who are immunosuppressed and considered to be at an increased risk of developing Pneumocystis carinii pneumonia.
Traveler’s Diarrhea in Adults: For the treatment of traveler’s diarrhea due to susceptible strains of enterotoxigenic E. coli.
BACTRIM is contraindicated in patients with a known hypersensitivity to trimethoprim or sulfonamides, in patients with a history of drug-induced immune thrombocytopenia with use of trimethoprim and/or sulfonamides, and in patients with documented megaloblastic anemia due to folate deficiency. BACTRIM is also contraindicated in pregnant patients and nursing mothers, because sulfonamides pass the placenta and are excreted in the milk and may cause kernicterus. BACTRIM is contraindicated in pediatric patients less than 2 months of age. BACTRIM is also contraindicated in patients with marked hepatic damage or with severe renal insufficiency when renal function status cannot be monitored.
FATALITIES ASSOCIATED WITH THE ADMINISTRATION OF SULFONAMIDES, ALTHOUGH RARE, HAVE OCCURRED DUE TO SEVERE REACTIONS, INCLUDING STEVENS-JOHNSON SYNDROME, TOXIC EPIDERMAL NECROLYSIS, FULMINANT HEPATIC NECROSIS, AGRANULOCYTOSIS, APLASTIC ANEMIA AND OTHER BLOOD DYSCRASIAS.
SULFONAMIDES, INCLUDING SULFONAMIDE-CONTAINING PRODUCTS SUCH AS SULFAMETHOXAZOLE/TRIMETHOPRIM, SHOULD BE DISCONTINUED AT THE FIRST APPEARANCE OF SKIN RASH OR ANY SIGN OF ADVERSE REACTION. In rare instances, a skin rash may be followed by a more severe reaction, such as Stevens-Johnson syndrome, toxic epidermal necrolysis, hepatic necrosis, and serious blood disorders (see PRECAUTIONS). Clinical signs, such as rash, sore throat, fever, arthralgia, pallor, purpura or jaundice may be early indications of serious reactions.
Cough, shortness of breath, and pulmonary infiltrates are hypersensitivity reactions of the respiratory tract that have been reported in association with sulfonamide treatment.
Thrombocytopenia has been reported with both sulfamethoxazole and trimethoprim usage. A case control study found a 124-fold increased risk of severe thrombocytopenia (platelets <30,000 µL, requiring hospitalization) with sulfamethoxazole and trimethoprim in combination with an incidence of 2 cases per 1000 patient-years of exposure.6 The incidence of less severe thrombocytopenia may be higher.
Thrombocytopenia caused by sulfamethoxazole and trimethoprim may be immune-mediated. Drug-induced immune-mediated thrombocytopenia with sulfamethoxazole/trimethoprim is characterized by a drug-dependent antibody that is itself nonreactive, but when soluble drug is present at pharmacologic concentrations, antibody binds tightly to specific platelet membrane glycoproteins, causing platelet destruction.7 Serologic testing for drug-specific antibody is commercially available and may be useful for identifying the specific cause of thrombocytopenia in individual cases. Testing is important because a patient with drug-dependent antibodies should not be re-exposed to BACTRIM (see CONTRAINDICATIONS).
Typically, a patient with immune thrombocytopenia will have taken drug for about 1 week or intermittently over a longer period of time (possibly years) before presenting with petechiae or bruising. Systemic symptoms, such as lightheadedness, chills, fever, nausea, and vomiting, often may precede bleeding events. Thrombocytopenia may be severe. Patients should have risk/benefit re-evaluated in order to continue treatment with BACTRIM. If the drug is stopped, symptoms usually resolve within 1 or 2 days and platelet count returns to normal in less than 1 week. If BACTRIM is not stopped, there is a risk of fatal hemorrhage. The onset of thrombocytopenia may be more rapid upon re-exposure.
Sulfamethoxazole has also been shown to occasionally trigger the production of platelet-specific autoantibodies leading to a clinical picture indistinguishable from spontaneous autoimmune thrombocytopenia. In such cases, autoantibodies remain present for up to 9 weeks after sulfamethoxazole has been stopped, corresponding with a marked reduction in platelet counts for the same period.
The sulfonamides should not be used for treatment of group A β-hemolytic streptococcal infections. In an established infection, they will not eradicate the streptococcus and, therefore, will not prevent sequelae such as rheumatic fever.
Clostridium difficile associated diarrhea (CDAD) has been reported with use of nearly all antibacterial agents, including BACTRIM, and may range in severity from mild diarrhea to fatal colitis. Treatment with antibacterial agents alters the normal flora of the colon leading to overgrowth of C. difficile.
C. difficile produces toxins A and B which contribute to the development of CDAD. Hypertoxin producing strains of C. difficile cause increased morbidity and mortality, as these infections can be refractory to antimicrobial therapy and may require colectomy. CDAD must be considered in all patients who present with diarrhea following antibiotic use. Careful medical history is necessary since CDAD has been reported to occur over two months after the administration of antibacterial agents.
If CDAD is suspected or confirmed, ongoing antibiotic use not directed against C. difficile may need to be discontinued. Appropriate fluid and electrolyte management, protein supplementation, antibiotic treatment of C. difficile , and surgical evaluation should be instituted as clinically indicated.
General: Prescribing Bactrim (sulfamethoxazole and trimethoprim) tablets in the absence of a proven or strongly suspected bacterial infection or a prophylactic indication is unlikely to provide benefit to the patient and increases the risk of the development of drug-resistant bacteria.
BACTRIM should be given with caution to patients with impaired renal or hepatic function, to those with possible folate deficiency (e.g., the elderly, chronic alcoholics, patients receiving anticonvulsant therapy, patients with malabsorption syndrome, and patients in malnutrition states) and to those with severe allergies or bronchial asthma. In glucose-6-phosphate dehydrogenase deficient individuals, hemolysis may occur. This reaction is frequently dose-related (see CLINICAL PHARMACOLOGY and DOSAGE AND ADMINISTRATION).
Cases of hypoglycemia in non-diabetic patients treated with BACTRIM are seen rarely, usually occurring after a few days of therapy. Patients with renal dysfunction, liver disease, malnutrition or those receiving high doses of BACTRIM are particularly at risk.
BACTRIM should be discontinued in case of any signs or symptoms of thrombocytopenia (see WARNINGS).
Hematological changes indicative of folic acid deficiency may occur in elderly patients or in patients with preexisting folic acid deficiency or kidney failure. These effects are reversible by folinic acid therapy.
Trimethoprim has been noted to impair phenylalanine metabolism, but this is of no significance in phenylketonuric patients on appropriate dietary restriction.
As with all drugs containing sulfonamides, caution is advisable in patients with porphyria or thyroid dysfunction.
Use in the Treatment of and Prophylaxis for Pneumocystis Carinii Pneumonia in Patients with Acquired Immunodeficiency Syndrome (AIDS): AIDS patients may not tolerate or respond to BACTRIM in the same manner as non-AIDS patients. The incidence of side effects, particularly rash, fever, leukopenia and elevated aminotransferase (transaminase) values, with BACTRIM therapy in AIDS patients who are being treated for Pneumocystis carinii pneumonia has been reported to be greatly increased compared with the incidence normally associated with the use of BACTRIM in non-AIDS patients.8 The incidence of hyperkalemia appears to be increased in AIDS patients receiving BACTRIM. Adverse effects are generally less severe in patients receiving BACTRIM for prophylaxis. A history of mild intolerance to BACTRIM in AIDS patients does not appear to predict intolerance of subsequent secondary prophylaxis.9 However, if a patient develops skin rash or any sign of adverse reaction, therapy with BACTRIM should be reevaluated (see WARNINGS).
High dosage of trimethoprim, as used in patients with Pneumocystis carinii pneumonia, induces a progressive but reversible increase of serum potassium concentrations in a substantial number of patients. Even treatment 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 is warranted in these patients.
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 sulfonamides.
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