What is the appropriate naproxen dose for a patient weighing 47 kg?

Naproxen Dosing for 47 kg Patient

For a patient weighing 47 kg, administer naproxen 5 to 7.5 mg/kg every 12 hours, which equals 235–352.5 mg per dose, rounded to a practical dose of 250 mg twice daily. 1

Weight-Based Dosing Calculation

• The European Society for Paediatric Anaesthesiology (ESPA) recommends 5 to 7.5 mg/kg every 12 hours for pediatric patients receiving naproxen 1
• For a 47 kg patient, this translates to:
  • Minimum dose: 235 mg (5 mg/kg × 47 kg)
  • Maximum dose: 352.5 mg (7.5 mg/kg × 47 kg)
• Practical dosing: Round to 250 mg twice daily as the starting dose, which can be increased to 375 mg twice daily if needed for adequate pain control 1

Dosing Schedule and Maximum Limits

• Administer every 12 hours (twice daily) 1
• The maximum daily dose should not exceed 1000 mg/day for routine long-term use in adults, though this patient's weight-based calculation keeps them well below this threshold 2
• For acute pain management, doses up to 550 mg every 12 hours may be used short-term, but this exceeds weight-based recommendations for a 47 kg patient 2

Route of Administration

• Oral administration is standard 1
• Taking naproxen with food may improve gastrointestinal tolerability 2

Monitoring Requirements for Use Beyond 10 Days

• Monitor blood pressure every 3 months to detect hypertension 2
• Check renal function (BUN and creatinine) quarterly 2
• Obtain liver function tests every 3 months 2
• Perform complete blood count quarterly 2
• Conduct fecal occult blood testing every 3 months 2

Critical Safety Considerations

• Discontinue immediately if gastrointestinal bleeding occurs 2
• Stop therapy if BUN or creatinine doubles 2
• Discontinue if liver function tests increase to 3× upper limit of normal 2
• Use with extreme caution in cardiovascular disease due to increased risk of ischemic cardiac events 2
• Avoid in moderate to severe renal impairment (creatinine clearance <30 mL/min) 2

Gastroprotection Strategy

• Consider proton pump inhibitor or H2 blocker in high-risk patients, including those ≥60 years, with history of peptic ulcer disease, or concurrent use of anticoagulants, antiplatelets, SSRIs, or glucocorticoids 2
• The risk of GI bleeding is dose-dependent across all NSAIDs 2

Common Pitfalls to Avoid

• Never combine with other NSAIDs without physician direction, as many patients inadvertently do this and increase adverse effect risk 2
• Be aware that naproxen is contraindicated in pregnancy (third trimester) due to risk of premature ductus arteriosus closure 3
• Avoid in nursing mothers as naproxen appears in breast milk at approximately 1% of maternal plasma concentration 3
• For patients with impaired renal function, dose adjustment may be necessary as naproxen is substantially excreted by the kidney 3

Alternative Considerations

• If two different NSAIDs fail sequentially, switch to an alternative analgesic approach rather than trying additional NSAIDs 2
• Consider topical NSAIDs to minimize systemic exposure for localized pain 2