IV Ceftriaxone Dosing for a 46 kg Patient
For a patient weighing 46 kg, the appropriate IV ceftriaxone dose is 80-100 mg/kg/day, which equals approximately 3.7-4.6 grams per day, divided every 12-24 hours, with a maximum daily dose of 4 grams. 1
Dosing Calculation Based on Weight
For a patient weighing 46 kg, the dosing options are:
Standard dosing approach: 80-100 mg/kg/day
- At 80 mg/kg/day: 46 kg × 80 mg/kg = 3,680 mg (3.7 g) daily
- At 100 mg/kg/day: 46 kg × 100 mg/kg = 4,600 mg (4.6 g) daily
Administration schedule:
- Single daily dose: 3.7-4 g IV once daily (maximum 4 g)
- Divided dose: 2 g IV every 12 hours (for doses exceeding 2 g)
Dosing Considerations
Weight-Based Dosing Thresholds
- Since the patient weighs 46 kg, which is just above the 45 kg threshold mentioned in guidelines, adult dosing protocols can be applied 1
- For patients weighing ≥45 kg, the maximum daily dose should not exceed 4 g 1, 2
Indication-Specific Dosing
Dosing may vary based on the specific infection being treated:
- For uncomplicated infections: 1-2 g IV daily
- For severe infections: 2 g IV every 12 hours (4 g total daily)
- For bacterial meningitis: 100 mg/kg/day (not to exceed 4 g daily) 1
Administration Method
- IV infusion should be administered over 30 minutes
- For doses exceeding 2 g daily, divide into twice-daily dosing (every 12 hours) 1, 2
Important Clinical Considerations
Pharmacokinetic Factors
- Ceftriaxone has a half-life of 5.8-8.7 hours in adults with normal renal function 2
- The drug is highly protein-bound (85-95%) and crosses the blood-brain barrier effectively 2
Monitoring
- No routine therapeutic drug monitoring is required for ceftriaxone
- Clinical response should be assessed within 48-72 hours of initiating therapy
Potential Pitfalls
- Underdosing risk: Recent research suggests that 1 g daily dosing may be insufficient for patients with normal or enhanced renal clearance 3
- Maximum dose limitation: Despite weight-based calculations suggesting 4.6 g for a 46 kg patient at 100 mg/kg/day, do not exceed the maximum adult dose of 4 g daily 1
- Calcium-containing solutions: Avoid concurrent administration with calcium-containing IV solutions due to precipitation risk 2
Conclusion
For a 46 kg patient, the appropriate ceftriaxone dose is 80-100 mg/kg/day (3.7-4 g/day), not exceeding 4 g total daily dose. For doses over 2 g daily, divide into twice-daily administration.