SULFAMETHOXAZOLE AND TRIMETHOPRIM

Sulfamethoxazole and Trimethoprim is a synthetic antibacterial combination product available in 800 mg sulfamethoxazole and 160 mg trimethoprim Double Strength tablets and 400 mg sulfamethoxazole and 80 mg trimethoprim tablets for oral administration. Each Double Strength tablet contains 800 mg sulfamethoxazole and 160 mg trimethoprim plus magnesium stearate, pregelatinized starch and sodium starch glycolate. Each tablet contains 400 mg sulfamethoxazole and 80 mg trimethoprim plus magnesium stearate, pregelatinized starch, and sodium starch glycolate. Trimethoprim is 2, 4-diamino-5-(3,4,5 trimethoxybenzyl) pyrimidine: the molecular formula is C 14 H 18 N 4 O 3 . It is a white to light yellow, odorless, bitter compound with a molecular weight of 290.3 and the following structural formula: Sulfamethoxazole is N 1 -(5-methyl-3-isoxazolyl) sulfanilamide; the molecular formula is C 10 H 11 N 3 O 3 S. It is almost white, odorless, tasteless compound with a molecular weight of 253.28 and the following structural formula: chemical structure chemical structure

: To reduce the development of drug-resistant bacteria and maintain the effectiveness of sulfamethoxazole and trimethoprim tablets and other antibacterial drugs, sulfamethoxazole and trimethoprim tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by susceptible bacteria R . When culture and susceptibility information are available, they should be considered in selecting or modifying antibacterial therapy. In the absence of such data, local epidemiology and susceptibility patterns may contribute to the empiric selection of therapy. Urinary Tract Infections: For the treatment of urinary tract infections due to susceptible strains of the following organisms: Escherichia coli, Klebsiella species, Enterobacter species, Morganella morganii, Proteus mirabilis and Proteus vulgaris. It is recommended that initial episodes of uncomplicated urinary tract infections be treated with a single effective antibacterial agent rather than the combination. Acute Otitis Media: For the treatment of acute otitis media in pediatric patients due to susceptible strains of pneumoniae or Haemophilus influenzae when in the judgment of the physician sulfamethoxazole and trimethoprim offers some advantage over the use of other antimicrobial agents. To date, there are limited data on the safety of repeated use of sulfamethoxazole and trimethoprim in pediatric patients under two years of age. Sulfamethoxazole and trimethoprim is not indicated for prophylactic or prolonged administration in otitis media at any age. 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 sulfamethoxazole and trimethoprim 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.

: Not recommended for use in pediatric patients less than 2 months of age. Urinary Tract Infections and Shigellosis in Adults and Pediatric Patients, and Acute Otitis Media in Children R Adults: The usual adult dosage in the treatment of urinary tract infections is 1 sulfamethoxazole and trimethoprim Double Strength tablet or 2 sulfamethoxazole and trimethoprim tablets every 12 hours for 10 to 14 days. An identical daily dosage is used for 5 days in the treatment of shigellosis. Children R : The recommended dose for Children R with urinary tract infections or acute otitis media is 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days. An identical daily dosage is used for 5 days in the treatment of shigellosis. The following table is a guideline for the attainment of this dosage: Children R 2 months of age and older: Weight Dose – every 12 hours lb kg Tablets 22 10 - 44 20 1 66 30 1½ 88 40 2 or 1 Double Strength tablet For Patients with Impaired Renal Function: When renal function is impaired, a reduced dosage should be employed using the following table: Creatinine Recommended Clearance (mL/min) Dosage Regimen Above 30 Usual standard regimen 15-30 1/2 the usual regimen Below 15 Use not recommended Acute Exacerbations of Chronic Bronchitis in Adults: The usual adult dosage in the treatment of acute exacerbations of chronic bronchitis is 1 sulfamethoxazole and trimethoprim Double Strength tablet or 2 sulfamethoxazole and trimethoprim tablets every 12 hours for 14 days. Pneumocystis Carinii Pneumonia: Treatment: Adults and Children R : The recommended dosage for patients with documented Pneumocystis carinii pneumonia is 75 to 100 mg/kg sulfamethoxazole and 15 to 20 mg/kg trimethoprim per 24 hours given in equally divided doses every 6 hours for 14 to 21 days11. The following table is a guideline for the upper limit of this dosage. Weight Dose – every 6 hours lb kg Tablets 18 8 - 35 16 1 53 24 1 ½ 70 32 2 or 1 Double Strength tablet 88 40 2 ½ 106 48 3 or 1 ½ Double Strength tablets 141 64 4 or 2 Double Strength tablets 176 80 5 or 2 ½ Double Strength tablets For the lower limit dose (75 mg/kg sulfamethoxazole and 15 mg/kg trimethoprim per 24 hours) administer 75% of the dose in the above table. Prophylaxis: Adults: The recommended dosage for prophylaxis in adults is 1 sulfamethoxazole and trimethoprim Double Strength tablet daily 12R Children R : For Children R , the recommended dose is 750 mg/m 2 /day sulfamethoxazole with 150 mg/m 2 /day trimethoprim given orally in equally divided doses twice a day, on 3 consecutive days per week. The total daily dose should not exceed 1600 mg sulfamethoxazole and 320 mg trimethoprim 13R The following table is a guideline for the attainment of this dosage in Children R : Body Surface Area Dose – every 12 hours (m 2 ) Tablets 0.26 - 0.53 ½ 1.06 1 Traveler’s Diarrhea in Adults: For the treatment of traveler’s diarrhea, the usual adult dosage is 1 sulfamethoxazole and trimethoprim Double Strength tablet or 2 sulfamethoxazole and trimethoprim tablets every 12 hours for 5 days.

: Sulfamethoxazole and trimethoprim is contraindicated in patients with a known hypersensitivity to trimethoprim or sulfonamides and in patients with documented megaloblastic anemia due to folate deficiency. Sulfamethoxazole and trimethoprim is also contraindicated in pregnant patients and nursing mothers, because sulfonamides pass the placenta and are excreted in the milk and may cause kernicterus. Sulfamethoxazole and trimethoprim is contraindicated in pediatric patients less than 2 months of age. Sulfamethoxazole and trimethoprim is also contraindicated in patients with marked hepatic damage or with severe renal insufficiency when renal function status cannot be monitored.

The most common adverse effects are gastrointestinal disturbances (nausea, vomiting, anorexia) and allergic skin reactions (such as rash and urticaria). 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 (SEE WARNINGS SECTION). Hematologic: Agranulocytosis, aplastic anemia, thrombocytopenia, leukopenia, neutropenia, hemolytic anemia, megaloblastic anemia, hypoprothrombinemia, methemoglobinemia, eosinophilia. Allergic Reactions: Stevens-Johnson syndrome, toxic epidermal necrolysis, anaphylaxis, allergic myocarditis, erythema multiforme, exfoliative dermatitis, angioedema, drug fever, chills, Henoch-Schoenlein purpura, serum sickness-like syndrome, generalized allergic reactions, generalized skin eruptions, photosensitivity, conjunctival and scleral injection, pruritus, urticaria and rash. In addition, periarteritis nodosa and systemic lupus erythematosus have been reported. Gastrointestinal: Hepatitis (including cholestatic jaundice and hepatic necrosis), elevation of serum transaminase and bilirubin, pseudomembranous enterocolitis, pancreatitis, stomatitis, glossitis, nausea, emesis, abdominal pain, diarrhea, anorexia. Genitourinary: Renal failure, interstitial nephritis, BUN and serum creatinine elevation, toxic nephrosis with oliguria and anuria, crystalluria and nephrotoxicity in association with cyclosporine. Metabolic and Nutritional: Hyperkalemia (see PRECAUTIONS: Use in the Treatment of and Prophylaxis for Pneumocystis Carinii Pneumonia in Patients with Acquired Immunodeficiency Syndrome (AIDS). Neurologic: Aseptic meningitis, convulsions, peripheral neuritis, ataxia, vertigo, tinnitus, headache. Psychiatric: Hallucinations, depression, apathy, nervousness. Endocrine: The sulfonamides bear certain chemical similarities to some goitrogens, diuretics (acetazolamide and the thiazides) and oral hypoglycemic agents. Cross-sensitivity may exist with these agents. Diuresis and hypoglycemia have occurred rarely in patients receiving sulfonamides. Musculoskeletal: Arthralgia and myalgia. Isolated cases of rhabdomyolysis have been reported with sulfamethoxazole and trimethoprim, mainly in AIDS patients. Respiratory: Cough, shortness of breath and R pulmonary infiltrates (see WARNINGS). Miscellaneous : Weakness, fatigue, insomnia.