Last reviewed: March 2026
This is an educational reference tool only. It does not replace clinical judgment, microbiological guidance, or institutional antibiotic stewardship policies.
Clavulanate levels, formulation availability, and dosing intervals should be verified against your local formulary and the child's clinical status before prescribing.
Amoxicillin-clavulanate (Augmentin) combines amoxicillin with clavulanic acid, a beta-lactamase inhibitor that extends the antibiotic's spectrum to cover organisms that would otherwise inactivate it. This combination is particularly effective against beta-lactamase-producing strains of H. influenzae, M. catarrhalis, S. aureus, and certain gram-negative enteric bacteria.
In pediatric practice, Augmentin is commonly prescribed for otitis media, sinusitis, animal bites, skin and soft tissue infections, urinary tract infections, and community-acquired pneumonia in children who have not responded to first-line amoxicillin.
The dosing of Augmentin is based on the amoxicillin component (25 or 45 mg/kg/day), but the clavulanate component has its own independent safety limit. The clavulanate limit of 10 mg/kg/day constrains which formulations and dose regimens are appropriate — this dual constraint is the primary complexity of Augmentin dosing.
Augmentin suspensions are available in several amoxicillin:clavulanate ratios, each suited to different dosing regimens. The ratio determines the clavulanate load per dose and is the key factor in selecting the appropriate formulation.
125/31.25 per 5 mL and 250/62.5 per 5 mL have a 4:1 ratio, suitable for standard TID dosing. 200/28.5 per 5 mL and 400/57 per 5 mL have a 7:1 ratio, better suited to BID dosing where the doubled dose per administration would otherwise deliver excessive clavulanate in a 4:1 formulation.
The 600/42.9 per 5 mL (14:1 ratio) formulation was specifically designed for high-dose amoxicillin BID regimens (90 mg/kg/day of amoxicillin) used in drug-resistant otitis media protocols in the USA, keeping clavulanate within the 10 mg/kg/day limit even at these high amoxicillin doses.
Enter the child's weight and age, select the dosing option (standard 40 mg/kg/day, high-dose, or custom), and choose the dosing interval (BID or TID). Select a suspension formulation; the calculator outputs the per-dose amoxicillin and clavulanate in mg, the volume of suspension, and the daily clavulanate total.
A clavulanate safety check is performed automatically. If the calculated daily clavulanate exceeds 10 mg/kg/day, an inline warning is displayed prompting formulation review or dose adjustment.
The calculator also evaluates tablet feasibility for older children, showing the number of tablets of a selected strength required per dose alongside the suspension result.
Per-dose and daily totals are shown for both the amoxicillin and clavulanate components separately, giving a complete picture of the combined exposure.
Clavulanic acid is responsible for the majority of Augmentin's gastrointestinal adverse effects — diarrhoea, nausea, and vomiting — which are far more common and more severe than those seen with plain amoxicillin at equivalent doses. The mechanism is a combination of disruption of gut flora and direct GI mucosal irritation from clavulanate.
The 10 mg/kg/day clavulanate limit is an empirically derived safety threshold that substantially reduces GI side effects while preserving beta-lactamase inhibition efficacy. Exceeding this limit significantly increases the rate of diarrhoea and treatment discontinuation.
When a standard formulation results in excess clavulanate at the required amoxicillin dose, the solution is to switch to a higher-ratio formulation (e.g., from 4:1 to 7:1) rather than reducing the amoxicillin dose — which would compromise efficacy.
Augmentin is not first-line for most common pediatric infections where plain amoxicillin is effective. Choosing Augmentin inappropriately increases the risk of side effects, promotes clavulanate-related diarrhoea, and contributes to antimicrobial selection pressure.
Augmentin is preferred when: beta-lactamase-producing organisms are documented or strongly suspected; the patient has failed a course of plain amoxicillin; the infection is a bite wound (animal or human) where polymicrobial coverage is needed; or for recurrent/resistant otitis media in areas with high local resistance rates.
Using 400/57 mg per 5 mL suspension (7:1 ratio, BID). Daily clavulanate is shown — values approaching 10 mg/kg/day should prompt formulation review.
| Weight (kg) | Daily amox dose (mg) | Per dose (mg amox) | mL per BID dose | Daily clavulanate (mg) |
|---|---|---|---|---|
| 5 kg | 200 mg | 100 mg | 1.25 mL | 28.5 mg |
| 8 kg | 320 mg | 160 mg | 2 mL | 45.6 mg |
| 10 kg | 400 mg | 200 mg | 2.5 mL | 57 mg |
| 12 kg | 480 mg | 240 mg | 3 mL | 68.4 mg |
| 15 kg | 600 mg | 300 mg | 3.75 mL | 85.5 mg |
| 18 kg | 720 mg | 360 mg | 4.5 mL | 102.6 mg |
| 20 kg | 800 mg | 400 mg | 5 mL | 114 mg |
| 25 kg | 1000 mg | 500 mg | 6.25 mL | 142.5 mg |
| 30 kg | 1200 mg | 600 mg | 7.5 mL | 171 mg |
| 40 kg | 1600 mg | 800 mg | 10 mL | 228 mg |
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Usman Shaoukat is the founder and editor of BestMedCal. He is a computer and web specialist who researches every BestMedCal tool from published standards and medication-safety references, including NIST, the U.S. FDA, NCBI and the American Academy of Pediatrics. His focus is dose-to-volume calculations and unit conversions. Every formula and worked example is checked against the sources listed on each page. BestMedCal has no clinicians on staff: our tools check arithmetic and explain methods; they do not recommend doses. If you spot an error, contact us and we will review it.