Appropriate Acetaminophen Dosing for 14-Year-Old, 45.9kg Patient for Preoperative Pain
For a 14-year-old patient weighing 45.9kg, the appropriate one-time preoperative dose of acetaminophen is 650-900mg (15-20mg/kg). This dosing provides effective preoperative pain management while maintaining safety parameters for pediatric patients in this age group 1.
Dosing Rationale
The appropriate dosing for acetaminophen in this adolescent patient follows these guidelines:
- For patients 5-18 years old: 15-20 mg/kg per dose is appropriate 1
- For this 45.9kg patient:
- Minimum dose: 45.9kg × 15mg/kg = 688.5mg (round to 650mg)
- Maximum dose: 45.9kg × 20mg/kg = 918mg (round to 900mg)
Administration Considerations
- Oral route is preferred when possible for preoperative medication 1
- Timing: Administer 30-60 minutes before the procedure for optimal effect
- Formulation options:
- Two 325mg tablets (650mg total)
- Three 325mg tablets (975mg total, slightly above calculated maximum)
- Two 500mg tablets (1000mg total, slightly above calculated maximum)
Role in Multimodal Analgesia
Acetaminophen serves as an excellent foundation for preoperative pain management:
- It's a cornerstone of multimodal analgesia with fewer side effects than opioids 1
- Helps reduce subsequent opioid requirements during and after surgery 1
- Provides effective analgesia with minimal risk of adverse effects when used at appropriate doses 1
Safety Considerations
- Acetaminophen has an excellent safety profile when used at appropriate doses 1
- Maximum daily dose should not exceed 75mg/kg/day or 4000mg/day (whichever is less)
- Avoid in patients with known liver dysfunction
- No contraindications with common preoperative medications
Clinical Pearls
- Acetaminophen should be administered at the beginning of the analgesic regimen for optimal effect 1
- It can be safely combined with NSAIDs if additional analgesia is needed, creating synergistic effects 1
- For ongoing pain management, acetaminophen should be the last analgesic to be discontinued when weaning pain medications 1
Common Pitfalls to Avoid
- Underdosing: Insufficient dosing leads to inadequate pain control
- Overdosing: Exceeding recommended doses increases risk of hepatotoxicity
- Failure to account for other acetaminophen-containing medications that may have been administered
- Not considering weight-based dosing in adolescents, which is more appropriate than adult fixed dosing
This evidence-based approach to acetaminophen dosing provides effective preoperative pain management while prioritizing patient safety for this 14-year-old patient.