Bactrim Dosing for a 14-Year-Old
For a 14-year-old patient, the recommended dose of Bactrim (sulfamethoxazole and trimethoprim) is 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours. 1
Weight-Based Dosing Guidelines
The FDA-approved dosing for Bactrim in pediatric patients is based on weight. For a 14-year-old, use the following weight-based guidelines:
- For a 14-year-old weighing approximately 40 kg (88 lb): 2 regular-strength tablets or 1 DS (double-strength) tablet every 12 hours 1
- For a 14-year-old weighing approximately 30 kg (66 lb): 1½ regular-strength tablets every 12 hours 1
Indication-Specific Considerations
The duration of treatment varies by indication:
- Urinary tract infections: 10-14 days
- Acute otitis media: 10 days
- Shigellosis: 5 days
Special Dosing Situations
For Pneumocystis jiroveci Pneumonia (PJP)
- Treatment: 75-100 mg/kg sulfamethoxazole and 15-20 mg/kg trimethoprim per 24 hours, divided every 6 hours for 14-21 days 1
- For a 40 kg adolescent: 2-2½ tablets or 1-1¼ DS tablets every 6 hours
For Prophylaxis
- 750 mg/m² sulfamethoxazole with 150 mg/m² trimethoprim daily in divided doses twice daily, 3 consecutive days per week 1
- Total daily dose should not exceed 1600 mg sulfamethoxazole and 320 mg trimethoprim
Monitoring and Safety
- Complete blood counts should be performed at initiation and periodically during treatment to monitor for hematologic toxicity 2
- Adequate hydration should be maintained to prevent crystalluria
- Dose adjustment is required for patients with impaired renal function:
- Creatinine clearance 15-30 mL/min: Half the usual dosage
- Creatinine clearance <15 mL/min: Not recommended 1
Important Considerations
- Bactrim is contraindicated in patients under 2 months of age 1
- Monitor for adverse effects including rash, gastrointestinal disturbances, and hematologic abnormalities
- Trimethoprim can interfere with creatinine secretion, causing a reversible increase in serum creatinine that does not reflect a true decrease in glomerular filtration rate 3
- Peak concentrations are higher and more reliable with IV administration compared to oral dosing 4
Practical Dosing Tips
- Administer with a full glass of water
- Can be given with food if gastrointestinal upset occurs
- Maintain adequate fluid intake during treatment to prevent crystalluria
- For adolescents who cannot swallow tablets, a suspension formulation is available
Remember that dosing should be based on the patient's actual weight and specific indication for treatment, with appropriate monitoring for adverse effects throughout the course of therapy.