Co-trimoxazole Syrup Dosage and Treatment Duration
For pediatric patients, the standard dosage of Co-trimoxazole (trimethoprim/sulfamethoxazole) syrup is 8 mg/kg/day of trimethoprim and 40 mg/kg/day of sulfamethoxazole divided into 2 doses, with treatment duration typically 7-14 days depending on the infection being treated. 1
Pediatric Dosing Guidelines
Standard Pediatric Dosing
- Urinary tract infections: 8 mg/kg/day trimethoprim and 40 mg/kg/day sulfamethoxazole divided into 2 doses every 12 hours for 10 days 1
- Shigellosis: Same dosage as above but for 5 days 1
- Acute otitis media: 8 mg/kg/day trimethoprim and 40 mg/kg/day sulfamethoxazole divided into 2 doses every 12 hours for 10 days 1
Weight-Based Dosing Guide for Children ≥2 months
| Weight (kg) | Weight (lb) | Dose (every 12 hours) |
|---|---|---|
| 10 | 22 | ½ tablet or equivalent syrup |
| 20 | 44 | 1 tablet or equivalent syrup |
| 30 | 66 | 1½ tablets or equivalent syrup |
| 40 | 88 | 2 tablets or equivalent syrup |
Prophylactic Dosing
For long-term prophylaxis in children with recurrent urinary tract infections:
- 2 mg/kg/day trimethoprim and 10 mg/kg/day sulfamethoxazole as a single daily dose 2
Adult Dosing Guidelines
- Urinary tract infections: 1 double-strength tablet (160mg/800mg) or 2 regular-strength tablets (80mg/400mg) every 12 hours for 10-14 days 1
- Shigellosis: Same dosage as above but for 5 days 1
- Traveler's diarrhea: 1 double-strength tablet or 2 regular-strength tablets every 12 hours for 5 days 1
- Skin infections: 1-2 double-strength tablets twice daily for 7-14 days 3
Special Populations
Renal Impairment
Dosage adjustment is required based on creatinine clearance:
- Creatinine clearance >30 mL/min: Standard regimen
- Creatinine clearance 15-30 mL/min: Half the usual regimen
- Creatinine clearance <15 mL/min: Not recommended 1
Pneumocystis jiroveci Pneumonia Treatment
- Higher doses required: 15-20 mg/kg/day trimethoprim and 75-100 mg/kg/day sulfamethoxazole divided into equal doses every 6 hours for 14-21 days 1
- For patients with chronic kidney disease:
- Creatinine clearance 10-50 mL/min: 3-5 mg/kg every 12 hours
- Creatinine clearance <10 mL/min: 3-5 mg/kg every 24 hours 4
Important Considerations
Age Restrictions
- Not recommended for infants less than 2 months of age 1
Contraindications
- Hypersensitivity to trimethoprim or sulfonamides
- Pregnancy (especially near term)
- Nursing mothers
- Megaloblastic anemia due to folate deficiency 3
Monitoring
- Patients should be monitored for clinical improvement within 48-72 hours
- If no improvement occurs, consider alternative antibiotic therapy 3
Adverse Effects
- Common: Gastrointestinal disturbances, skin rash
- Severe but rare: Stevens-Johnson syndrome, toxic epidermal necrolysis 3
- Higher incidence of side effects with higher single doses 5, 6
Treatment Duration Considerations
- For uncomplicated UTIs in adults, shorter courses (1-5 days) may be effective 5, 6, 7
- For more serious infections like pneumonia or complicated skin infections, longer courses (7-14 days) are typically required 3, 1
Clinical Pearls
- Once-daily dosing regimens may improve compliance compared to twice-daily regimens 7
- Co-trimoxazole has been shown to be effective against MRSA in skin and soft tissue infections 3
- Adequate fluid intake should be maintained during treatment to prevent crystalluria
- Complete the entire prescribed course of antibiotics even if symptoms improve before completion
Remember that the choice of co-trimoxazole as an antibiotic should consider local resistance patterns, especially in areas where resistance is high, amoxicillin may be preferred for certain infections 4.