Pharm

Sulfonamide

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Sulfonamide, Bactrim, Sulfatrim, Co-trimoxazole, Trimethoprim Sulfamethoxazole, Septra, TMP-SMZ

  • Indications
  1. Urinary Tract Infection
  2. Pneumocystis carinii prophylaxis and treatment
  • Contraindications
  1. Avoid in infant under age 2 months
  2. Sulfonamide Allergy
  • Adverse Effects
  • General
  1. Allergic Reaction or Anaphylaxis
    1. See Sulfonamide Allergy
  2. Bone Marrow suppression (Agranulocytosis)
  3. Steven's Johnson Syndrome
  4. Toxic Epidermal Necrolysis
  5. Hyperkalemia
    1. Related to trimethoprim component
    2. Higher risk with underlying Renal Insufficiency
    3. Exacerbated by ACE Inhibitor, Angiotensin Receptor Blocker, and Potassium supplements
  • Adverse Effects
  • HIV patients (40-60% within 3 weeks)
  1. Hepatitis
  2. Neutropenia
  3. Anemia
  4. Hyponatremia
  5. Hyperkalemia (6% of patients, esp. elderly)
  6. Nausea or Vomiting
  7. Rash
  8. Fever
  • Drug Interactions
  1. Other drugs decrease Trimethoprim Sulfamethoxazole levels
    1. Rifampin
  2. Trimethoprim Sulfamethoxazole increases other drug levels
    1. Phenytoin (Dilantin)
    2. Methotrexate
    3. Warfarin
      1. Trimethoprim Sulfamethoxazole increases Warfarin effects and may result in up to a 3 fold increase in INR
      2. Monitor INR and plan 25-50% Warfarin dose reduction while on Trimethoprim Sulfamethoxazole
  3. Hyperkalemia risk
    1. Increased risk with ACE Inhibitors, Angiotensin Receptor Blockers, Spironolactone
    2. Higher risk with age >65 years, Renal Insufficiency, Diabetes Mellitus and Heart Failure
    3. Significantly increased rate of hospitalization and sudden death
    4. Avoid Septra use for longer than three days with these agents and comorbidities in age >65 years
    5. Consider alternative antibiotics, holding antihypertensive or recheck Serum Potassium in 4-5 days
    6. Fralick (2014) BMJ 349:g6196 +PMID:25359996 [PubMed]
  4. References
    1. Tarascon Pharmacopoeia, accessed online 8/8/2014
    2. (2014) Presc lett 21(8): 47
  • Precautions
  1. Prolonged use may cause very severe adverse reactions
  2. Follow CBC in prolonged use
  3. Hyperkalemia risk (especially in Renal Insufficiency)
  • Preparations
  1. Double Strength (DS)
    1. Trimethoprim 160 mg
    2. Sulfamethoxazole 800 mg
  2. Single Strength (SS)
    1. Trimethoprim 80 mg
    2. Sulfamethoxazole 400 mg
  3. Pediatric Suspension (40/200 per 5 ml)
    1. Trimethoprim 40 mg per 5 ml
    2. Sulfamethoxazole 200 mg per 5 ml
  • Dosing
  • Directions (regarding Sulfonamide component)
  1. Take on an empty Stomach
  2. Take more than 1 hour before or two hours after food
  • Dosing
  • Children (Using 40/200 per 5 ml suspension)
  1. Treatment
    1. Dose 8 mg/kg/day of TMP component PO divided bid
    2. For each 10 kg weight, dose 5 ml suspension bid
    3. Examples
      1. Age 2 months (5 kg): 2.5 cc PO bid
      2. Age 1 year (10 kg): 5.0 cc PO bid
      3. Age 3 years (15 kg): 7.5 cc PO bid
      4. Age 5 years (20 kg): 10 cc PO bid
  2. Prophylaxis of Urinary Tract Infections
    1. Dose: 4 mg/kg/day of Trimethoprim dosed once daily
    2. Avoid use with marked Hyperbilirubinemia
  • Dosing
  • Adults
  1. Standard: 1 DS tablet orally twice daily
  2. Cellulitis: 1-2 DS tablet orally twice daily
  1. Creatinine Clearance: 15-30 ml/min
    1. Decrease Trimethoprim-Sulfamethoxazole dose by 50%
  2. Creatinine Clearance: <15 ml/min
    1. Avoid the use of Trimethoprim Sulfamethoxazole
  3. References
    1. Tarascon Pharmacopoeia, accessed online 8/8/2014
  • Dosing
  • HIV
  1. Pneumocystis: PO or IV (15 mg/kg of trimethoprim/day)