About

Incorrect pediatric antibiotic dosing is a documented source of treatment failure and antimicrobial resistance. Amoxicillin remains the first-line agent for acute otitis media, streptococcal pharyngitis, community-acquired pneumonia, and urinary tract infections in children per AAP and IDSA guidelines. The therapeutic window depends on the pathogen's MIC: standard-dose regimens use 25 - 50 mg/kg/day while high-dose regimens for resistant S. pneumoniae require 80 - 90 mg/kg/day. This calculator applies weight-based dosing (D = W × R) divided by the prescribed frequency, then converts milligrams to milliliters of suspension using the selected formulation concentration. It cross-checks the child's weight against age-based WHO reference ranges and caps output at adult maximum doses. This tool approximates dosing assuming normal renal function and no contraindications. Always confirm with the prescribing physician.

Formulas

The per-dose amount in milligrams is derived from the child's body weight, the indication-specific rate, and the dosing frequency:

D_dose = W × RF

where W = patient weight in kg, R = dose rate in mg/kg/day (from guideline), and F = number of doses per day (2 for BID, 3 for TID). The result is capped so that D_dose ≤ D_max (adult ceiling per dose).

Volume of suspension per dose:

V = D_doseC

where C = concentration of the suspension in mg/mL (e.g., 125 mg per 5 mL = 25 mg/mL). The total daily volume is V_daily = V × F.

Reference Data

Indication	Dose Rate	Frequency	Duration	Max Daily Dose	Guideline
Acute Otitis Media (standard)	40 - 45 mg/kg/day	BID or TID	10 days	1500 mg	AAP 2013
Acute Otitis Media (high-dose)	80 - 90 mg/kg/day	BID	10 days	3000 mg	AAP 2013
Strep Pharyngitis	50 mg/kg/day	BID or TID	10 days	1000 mg	IDSA 2012
Community-Acquired Pneumonia	90 mg/kg/day	BID	7 - 10 days	3000 mg	IDSA/PIDS 2011
Sinusitis (standard)	45 mg/kg/day	BID or TID	10 - 14 days	1500 mg	AAP 2013
Sinusitis (high-dose)	80 - 90 mg/kg/day	BID	10 - 14 days	3000 mg	IDSA 2012
UTI (Uncomplicated)	25 - 50 mg/kg/day	TID	7 - 10 days	1500 mg	AAP 2011
Skin & Soft Tissue	25 - 50 mg/kg/day	TID	7 - 10 days	1500 mg	Red Book
Dental Abscess	25 - 50 mg/kg/day	TID	5 - 7 days	1500 mg	ADA 2019
Endocarditis Prophylaxis	50 mg/kg (single)	Once	Single dose	2000 mg	AHA 2007
Lyme Disease (early)	50 mg/kg/day	TID	14 - 21 days	1500 mg	IDSA 2006
H. pylori (combination)	50 mg/kg/day	BID	14 days	1000 mg	NASPGHAN 2011
Post-splenectomy Prophylaxis	20 mg/kg/day	BID	Ongoing	500 mg	BCSH 2011

Frequently Asked Questions

Standard-dose (40 - 45 mg/kg/day) targets susceptible organisms. High-dose (80 - 90 mg/kg/day) is recommended when penicillin-resistant Streptococcus pneumoniae is suspected - typically in children under 2 years, those in daycare, or those who received antibiotics within 30 days. The higher dose exceeds the MIC breakpoint of intermediate-resistant strains.

Amoxicillin is approximately 60% renally excreted. For GFR < 30 mL/min/1.73m², the dosing interval should be extended to every 12 - 24 hours rather than reducing the per-dose amount. This calculator assumes normal renal function. Adjust manually for impaired clearance.

Large volumes reduce adherence in small children. Switch to a higher-concentration formulation. For example, moving from 125 mg/5 mL (25 mg/mL) to 400 mg/5 mL (80 mg/mL) reduces volume by a factor of 3.2. The calculator provides volume for all available formulations to facilitate this comparison.

Current AAP guidelines recommend actual body weight for amoxicillin dosing in children, but the daily total must not exceed the adult maximum ceiling. For significantly obese children (BMI > 95th percentile), some clinicians use adjusted body weight. This calculator flags when the entered weight exceeds the 97th WHO percentile for the given age.

Amoxicillin suspension can be mixed with milk, formula, or juice immediately before administration without significant bioavailability loss. However, mixing with hot liquids degrades the drug. Reconstituted suspension must be refrigerated and discarded after 14 days. Shake well before each dose.

This calculator covers amoxicillin alone. Amoxicillin-clavulanate (Augmentin) has a separate dosing schedule because the clavulanate component is capped at 6.4 mg/kg/day to avoid GI side effects. High-dose amox-clav uses a 14:1 ratio formulation specifically to allow 90 mg/kg/day of amoxicillin without exceeding the clavulanate limit.