Amoxicillin 400mg/5ml Dosage for a 160-pound Adult
For a 72.6 kg (160 lb) adult with normal renal function, the standard amoxicillin dosage is 500 mg every 8 hours or 875 mg every 12 hours for most infections, which translates to approximately 12.5-15 mL of the 400mg/5mL suspension every 8-12 hours depending on infection severity. 1
Standard Adult Dosing
The FDA-approved dosing for adults weighing more than 40 kg is based on infection severity 1:
- Mild to moderate infections (ear/nose/throat, skin, genitourinary): 500 mg every 12 hours OR 250 mg every 8 hours 1
- Severe infections: 875 mg every 12 hours OR 500 mg every 8 hours 1
- Lower respiratory tract infections (any severity): 875 mg every 12 hours OR 500 mg every 8 hours 1
Converting to 400mg/5mL Suspension
For the 400mg/5mL (80mg/mL) suspension formulation:
- 500 mg dose = 6.25 mL of suspension
- 875 mg dose = approximately 11 mL of suspension
- 250 mg dose = 3.125 mL of suspension
Critical Considerations for Renal Impairment
If this patient has impaired renal function, dosing adjustments are mandatory to prevent drug accumulation 1, 2:
Severe Renal Impairment Dosing 1
- GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours (depending on infection severity)
- GFR <10 mL/min: 500 mg or 250 mg every 24 hours
- Hemodialysis patients: 500 mg or 250 mg every 24 hours, with an additional dose during and at the end of dialysis
Important caveat: Patients with GFR <30 mL/min should NOT receive the 875 mg dose 1. Regular monitoring of renal function is recommended during treatment in patients with severely impaired renal function 2.
Administration Guidelines
- Take at the start of a meal to minimize gastrointestinal intolerance 1
- Shake suspension well before each use 1
- Store reconstituted suspension in refrigerator (preferred but not required); discard after 14 days 1
- Continue treatment for minimum 48-72 hours beyond symptom resolution or bacterial eradication 1
Common Pitfalls to Avoid
- Do not use 875 mg dosing in renal impairment (GFR <30 mL/min) as this can lead to excessive drug accumulation 1
- Verify renal function before prescribing - the expanded question mentions "potential impaired renal function," which necessitates dose adjustment 2
- Ensure adequate dosing intervals based on creatinine clearance to prevent toxicity 2
- Amoxicillin is better absorbed than ampicillin, achieving 2-2.5 times higher blood levels, making it the preferred oral aminopenicillin 3