Common Dosing Strengths of Amoxicillin
Amoxicillin is available in multiple oral formulations with suspension strengths of 125 mg/5 mL and 250 mg/5 mL, capsule strengths of 250 mg and 500 mg, and tablet strengths including 875 mg, with chewable tablets available in 400 mg strength. 1
Oral Suspension Formulations
Suspension concentrations of 125 mg/5 mL and 250 mg/5 mL are the standard pediatric formulations, with each 5 mL of reconstituted suspension containing the specified amoxicillin dose as the trihydrate. 1
The 125 mg/5 mL suspension contains 0.11 mEq (2.51 mg) of sodium per 5 mL, while the 250 mg/5 mL suspension contains 0.15 mEq (3.36 mg) of sodium per 5 mL. 1
A 400 mg/5 mL suspension formulation is also available and produces comparable pharmacokinetic parameters to the 400 mg chewable tablet. 1
Capsule and Tablet Strengths
Capsules are available in 250 mg and 500 mg strengths, producing average peak blood levels of 3.5–5.0 mcg/mL and 5.5–7.5 mcg/mL respectively, 1–2 hours after administration. 1
The 875 mg tablet is a high-strength formulation that produces an AUC of 35.4 ± 8.1 mcg·hr/mL and a Cmax of 13.8 ± 4.1 mcg/mL when administered at the start of a light meal. 1
Chewable tablets in 400 mg strength are available and yield an AUC of 17.9 (±2.4) mcg·hr/mL and Cmax of 5.18 (±1.64) mcg/mL. 1
Clinical Dosing Context
Standard-Dose Regimens
"Typical" adult dosing is 1.5 to 1.75 g/day (equivalent to 500 mg three times daily or 875 mg twice daily), while typical pediatric dosing is 40 to 45 mg/kg per day. 2
These standard doses are appropriate for mild-to-moderate infections caused by susceptible organisms. 2
High-Dose Regimens
High-dose amoxicillin is defined as 4 g/day for adults and 90 mg/kg per day for children, designed to overcome relative penicillin resistance in Streptococcus pneumoniae with elevated MICs. 2
High-dose amoxicillin-clavulanate consists of 4 g of amoxicillin with 250 mg of clavulanate per day for adults, and 90 mg/kg per day of amoxicillin with 6.4 mg/kg per day of clavulanate (14:1 ratio) in two divided doses for children. 2, 3
The only FDA-approved formulations of high-dose amoxicillin are in combination with clavulanate, with the adult formulation using a modified-release mechanism and the pediatric formulation providing the 14:1 ratio in oral suspension. 2
Important Prescribing Considerations
Serum levels of amoxicillin increase linearly with dose, meaning gastrointestinal absorption is not a limiting factor, and the difference in adverse effects between lower and higher doses is negligible. 2
Amoxicillin is stable in gastric acid and rapidly absorbed after oral administration, with peak concentrations occurring approximately 1 hour after dosing. 1
The half-life of amoxicillin is 61.3 minutes, with approximately 60% of an orally administered dose excreted unchanged in the urine within 6 to 8 hours. 1
Dosage adjustment is required in patients with severe renal impairment (GFR <30 mL/min) since amoxicillin is primarily eliminated by the kidney. 1