What is the recommended dosage of amoxicillin (amoxicillin) for a patient weighing 47.6 pounds?

Amoxicillin Dosage for a 47.6 Pound Patient

For a patient weighing 47.6 pounds (21.6 kg), the recommended amoxicillin dosage is 40-45 mg/kg/day divided into 2-3 doses, which equals approximately 865-972 mg per day or 288-324 mg per dose given three times daily. 1

Dosage Calculation

• 47.6 pounds = 21.6 kg (conversion factor: 1 pound = 0.454 kg) 2
• According to the FDA label, the recommended amoxicillin dosage for most infections is:
  • For mild/moderate infections: 25 mg/kg/day divided every 12 hours or 20 mg/kg/day divided every 8 hours 1
  • For severe infections: 45 mg/kg/day divided every 12 hours or 40 mg/kg/day divided every 8 hours 1

Specific Dosing by Infection Type

For Respiratory Tract Infections

• For lower respiratory tract infections (mild/moderate or severe): 45 mg/kg/day in divided doses every 12 hours or 40 mg/kg/day in divided doses every 8 hours 1
  • This equals approximately 972 mg/day or 324 mg per dose three times daily

For Skin/Skin Structure Infections

• For mild/moderate infections: 25 mg/kg/day in divided doses every 12 hours or 20 mg/kg/day in divided doses every 8 hours 1
  • This equals approximately 540 mg/day or 180 mg per dose three times daily
• For severe infections: 45 mg/kg/day in divided doses every 12 hours or 40 mg/kg/day in divided doses every 8 hours 1
  • This equals approximately 972 mg/day or 324 mg per dose three times daily

For Streptococcal Pharyngitis

• Amoxicillin 50 mg/kg once daily (maximum = 1,000 mg) or 25 mg/kg twice daily (maximum = 500 mg) for 10 days 3
  • This equals approximately 1,080 mg once daily or 540 mg twice daily

Important Considerations

• Duration of therapy should be continued for a minimum of 48 to 72 hours beyond the time that the patient becomes asymptomatic 1
• For Streptococcal infections, a minimum of 10 days of treatment is recommended to prevent acute rheumatic fever 1, 4
• For patients under 12 weeks of age, the recommended upper dose is 30 mg/kg/day divided every 12 hours due to incompletely developed renal function 1
• To minimize gastrointestinal intolerance, amoxicillin should be taken at the start of a meal 1

Dosage Form Selection

• For pediatric patients, oral suspension is often preferred:
  • Available strengths: 125 mg/5 mL or 250 mg/5 mL 1
  • For a 21.6 kg child receiving 324 mg per dose, approximately 6.5 mL of the 250 mg/5 mL suspension would be required 1

Clinical Pearls

• Always verify patient weight in kilograms before prescribing weight-based medications to ensure accurate dosing 2
• The pharmacodynamic efficacy target of amoxicillin is 40% time above the minimal inhibition concentration (40%T > MIC) 5
• For more resistant organisms, higher doses may be required to maintain adequate drug concentrations 5, 6
• Amoxicillin is often used in place of oral penicillin V in young children due to better taste acceptance of the suspension 4