How to Write an Amoxicillin Prescription
Write amoxicillin prescriptions with weight-based dosing (mg/kg/day), specify the total daily dose, number of divided doses per day, duration of therapy, the indication, and the patient's weight directly on the prescription. 1
Essential Prescription Components
When writing an amoxicillin prescription, include these critical elements to ensure safe and effective dosing:
- Patient's weight (essential for accurate dosing)
- Total daily dose in mg/kg/day
- Number of divided doses (e.g., twice daily or three times daily)
- Duration of therapy (in days)
- Clinical indication (e.g., acute otitis media, pneumonia, pharyngitis)
Dosing by Age and Indication
Adults and Children ≥40 kg 2
For most common infections:
- Mild to moderate infections: 500 mg every 12 hours OR 250 mg every 8 hours
- Severe infections: 875 mg every 12 hours OR 500 mg every 8 hours
Children ≥3 Months and <40 kg 2
Standard dosing for most infections:
- Mild to moderate: 25 mg/kg/day divided every 12 hours OR 20 mg/kg/day divided every 8 hours
- Severe infections or pneumonia: 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours
High-dose amoxicillin (for resistant pneumococcal infections):
- 80-90 mg/kg/day for acute otitis media, sinusitis, or pneumonia where pneumococcal resistance is a concern 3
Specific condition-based dosing:
- Acute otitis media: 40 mg/kg twice daily for 5 days 4
- Acute pharyngitis (GAS): Standard dosing with penicillin as alternative 3
- Community-acquired pneumonia: 80-100 mg/kg/day in three divided doses for children <30 kg 5
Infants <3 Months (12 weeks) 2
- Maximum 30 mg/kg/day divided every 12 hours due to immature renal function
- Treatment duration: minimum 48-72 hours beyond symptom resolution
Administration Instructions
Key counseling points to include 2:
- Take at the start of a meal to minimize gastrointestinal intolerance 2
- Shake oral suspension well before each use
- Use a calibrated oral syringe for liquid formulations in children
- Refrigeration is preferable but not required for suspension
- Discard unused suspension after 14 days
- Complete the full course even if feeling better
Duration of Therapy
- Most infections: Minimum 48-72 hours beyond symptom resolution 2
- Streptococcal pharyngitis: Minimum 10 days to prevent acute rheumatic fever 3, 2
- H. pylori eradication: 14 days (triple or dual therapy) 2
Renal Dosing Adjustments
For patients with severe renal impairment 2:
- GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours
- GFR <10 mL/min: 500 mg or 250 mg every 24 hours
- Hemodialysis: Additional dose during and after dialysis
- Do NOT use 875 mg dose if GFR <30 mL/min
Common Pitfalls to Avoid
Age-based vs. weight-based dosing: Always use weight-based dosing rather than age bands for accuracy 6. Studies show significant dosing disparities when age alone is used, with larger children often receiving inadequate doses per kilogram 7.
"Adult maximum dose" trap: Don't artificially cap doses at "adult maximums" for larger children who still require weight-based dosing. Children >60 kg frequently receive subtherapeutic doses when capped at adult maximums 7.
Inadequate prescription details: Prescriptions lacking weight, indication, and specific dosing instructions lead to unnecessary pharmacist-prescriber consultations and potential dosing errors 6.
Penicillin allergy: Document true allergy history; many reported "allergies" are not IgE-mediated hypersensitivity 1.
Sample Prescription Format
Amoxicillin 250 mg/5 mL oral suspension
- Patient weight: 15 kg
- Dose: 45 mg/kg/day = 675 mg/day
- Give: 6.75 mL (337.5 mg) twice daily
- Duration: 10 days
- Indication: Acute otitis media
- Dispense: 150 mL bottle
- Instructions: Shake well. Give 6.75 mL by mouth twice daily with food. Complete full course.