About amoxicillin
Amoxicillin is a broad-spectrum aminopenicillin antibiotic and the most commonly prescribed antibiotic for children in the United States. It is the first-line agent for acute otitis media, group A streptococcal pharyngitis (strep throat), uncomplicated community-acquired pneumonia in non-MRSA settings, and uncomplicated pediatric urinary tract infection. It works by inhibiting bacterial cell wall synthesis (binding penicillin-binding proteins) and is well absorbed orally, with peak plasma levels at 1-2 hours.
The two most important dosing levers for parents and prescribers are weight (every pediatric dose is calculated in mg/kg) and indication - the same child can need anywhere from 25 to 90 mg/kg/day depending on whether the infection is mild skin cellulitis or a high-resistance AOM.
How the dose calculation works
- Look up the target mg/kg/day for the indication and severity. The AAP table starts at 25-50 mg/kg/day for mild infections and goes up to 80-90 mg/kg/day for high-dose AOM and pneumonia.
- Multiply by child weight in kg to get total daily mg. Cap at 3000 mg/day (and 1000 mg per dose) for older children.
- Divide by the dosing frequency. BID (twice daily, every 12 hours) is used for AOM and strep. TID (three times daily, every 8 hours) is used for pneumonia, UTI and skin infections.
- Convert mg to mL using the concentration of suspension on hand. 400 mg/5mL = 80 mg/mL, 250 mg/5mL = 50 mg/mL, 125 mg/5mL = 25 mg/mL.
- Round to the nearest 0.5 mL using an oral syringe. Most pharmacies dispense 100 mL or 150 mL bottles - the tool tells you how many days of therapy that covers.
- Capsules (250 mg, 500 mg) are not split, so the prescribed dose rounds to the nearest capsule. Capsules are typically not used in children under 8 years who cannot swallow them.
Indication and dosing reference
The AAP and IDSA dosing summary for otherwise healthy children:
| Indication | mg/kg/day | Frequency | Duration | Source |
|---|---|---|---|---|
| Otitis media (AOM) | 80-90 | BID (q12h) | 10 d (under 2 y), 5-7 d (older) | AAP 2013 |
| Strep pharyngitis | 50 | BID or daily | 10 days | IDSA 2012 |
| Community-acquired pneumonia | 90 | TID (q8h) | 5-10 days | IDSA 2011 |
| UTI (uncomplicated) | 25-50 | TID | 7-10 days | AAP 2011 |
| Skin/soft tissue (non-MRSA) | 25-50 | TID | 5-10 days | IDSA 2014 |
| Mild general infection | 25-50 | BID-TID | 5-10 days | Lexi-Comp |
Maximum dose: 1000 mg per dose, 3000 mg per day. Dose-adjust for renal impairment (creatinine clearance under 30 mL/min) per Lexi-Comp.
Same child, different formulations
How mL per dose changes for a 20 kg child treated for moderate AOM (90 mg/kg/day BID = 900 mg per dose):
| Formulation | mg/mL | mL per dose | Doses in 100 mL | Suitability |
|---|---|---|---|---|
| 125 mg/5 mL suspension | 25 mg/mL | 36 mL | 2-3 doses | Too dilute - very large volume |
| 250 mg/5 mL suspension | 50 mg/mL | 18 mL | 5-6 doses | Workable but large |
| 400 mg/5 mL suspension | 80 mg/mL | 11.5 mL | 8-9 doses | Standard for high-dose AOM |
| 250 mg capsule | 250 mg each | 3-4 capsules | n/a | Age 8+, can swallow capsule |
| 500 mg capsule | 500 mg each | 2 capsules | n/a | Age 8+, simpler regimen |
Dose by weight (visual)
Total daily dose in mg for the selected indication and severity across common pediatric weights:
Bar height = total daily mg. Dashed line at 3000 mg shows the adult-level daily cap.
Worked example: 20 kg child with acute otitis media
A 3-year-old, 20 kg child diagnosed with acute otitis media. AAP high-dose protocol: 90 mg/kg/day BID for 10 days.
- Total daily mg: 20 kg × 90 mg/kg = 1800 mg/day.
- Per dose mg: 1800 / 2 = 900 mg every 12 hours.
- Volume with 400 mg/5 mL suspension: 900 / 80 = 11.25 mL per dose (rounded to 11.5 mL on a 10 mL oral syringe).
- Volume with 250 mg/5 mL: 900 / 50 = 18 mL per dose - workable but much larger volume.
- Total course: 22.5 mL/day × 10 days = 225 mL. A 100 mL bottle covers ~4.4 days, a 150 mL bottle ~6.7 days, so a 250 mL fill is needed.
- Co-administration: Tylenol 15 mg/kg every 4-6 hours (300 mg = 9 mL of 160 mg/5 mL) or ibuprofen 10 mg/kg every 6-8 hours is safe alongside the antibiotic.
When NOT to use amoxicillin
| Scenario | Reason |
|---|---|
| Penicillin allergy | Cross-reactivity with all penicillins. Use macrolide (azithromycin) or clindamycin. |
| Recurrent AOM in last 30 days | Beta-lactamase resistance likely. Use amoxicillin-clavulanate. |
| Viral upper respiratory infection | Antibiotics do not work on viruses and contribute to resistance. |
| Infectious mononucleosis | Can cause an almost universal morbilliform rash (not a true allergy). |
| MRSA-confirmed skin infection | Inadequate MRSA coverage. Use clindamycin or trimethoprim-sulfamethoxazole. |
| Severe renal impairment (CrCl < 10) | Dose adjustment required - dose by physician only. |
Practical tips for parents
- Use an oral syringe, not a kitchen spoon. Pharmacies provide free oral syringes calibrated in 0.5 mL graduations. A teaspoon varies from 3-7 mL.
- Shake the bottle vigorously every time. Reconstituted suspension settles - underdosing happens when you draw from the top of an unshaken bottle.
- Complete the full course. Even if symptoms resolve in 2-3 days (and they often do for AOM), stopping early can fail to clear the infection and breeds resistance.
- Set alarms. BID = roughly 7 am and 7 pm. TID = 7 am, 3 pm, 11 pm. Spacing matters more than time of day.
- Probiotics for diarrhea. If amoxicillin causes loose stools, ask your pediatrician about Lactobacillus or Saccharomyces probiotics, taken 2-3 hours apart from the antibiotic.
- Watch for rash. An itchy hives-like rash, swelling around the lips or face, or any breathing difficulty in the first 24-48 hours is a medical emergency.
Wait-and-see option for AOM
For children 24 months and older with non-severe unilateral otitis media, the AAP permits a 48-72 hour observation window before starting antibiotics. About 60% of mild AOM resolves spontaneously. Many pediatricians issue a "safety net" amoxicillin prescription that the parent only fills if symptoms persist or worsen at 48 hours. This approach reduces unnecessary antibiotic use without compromising outcomes.
Frequently asked questions
How much amoxicillin should I give my child by weight?
The typical pediatric amoxicillin dose is 25-50 mg/kg/day in 2-3 divided doses for mild to moderate infections. For acute otitis media the AAP recommends high-dose 80-90 mg/kg/day in 2 divided doses (BID). For strep pharyngitis the dose is 50 mg/kg/day BID for 10 days. For CAP 90 mg/kg/day TID. Maximum 1000 mg per dose and 3000 mg per day.
What is the correct amoxicillin dose for ear infection?
The AAP recommends 80-90 mg/kg/day of amoxicillin divided BID for otitis media in children 6 months and older. For a 20 kg child this is 1600-1800 mg per day, given as 800-900 mg every 12 hours. With 400 mg/5mL suspension that is 10-11 mL per dose. Duration is typically 10 days for children under 2 and 5-7 days for older children.
Can I give amoxicillin to a child with penicillin allergy?
No. Amoxicillin is in the penicillin family (aminopenicillin) and is contraindicated in children with documented penicillin allergy. Alternative antibiotics include azithromycin, clindamycin or cefdinir depending on the infection. Always tell your pediatrician about any drug allergies before starting any antibiotic.
What are common side effects of amoxicillin in children?
Common side effects include diarrhea (5-15% of children), nausea or vomiting, mild rash and yeast infection or diaper rash. A non-itchy delayed maculopapular rash on day 5-10 (the so-called amoxicillin rash) is usually not a true allergic reaction. Hives, swelling, breathing difficulty or anaphylaxis are emergencies - stop the medication and seek immediate care.
What if I miss a dose of my child's amoxicillin?
Give the missed dose as soon as you remember. If it is almost time for the next scheduled dose, skip the missed dose and resume the normal schedule. Do not double up. Try to keep doses spaced as evenly as possible (every 8 or 12 hours depending on frequency). Missing one dose rarely causes treatment failure, but missing multiple doses can.
Can amoxicillin be given with milk or food?
Yes. Amoxicillin can be given with or without food. Giving it with a small amount of food, formula, applesauce or juice often helps if the child finds the taste unpleasant or experiences stomach upset. Unlike some other antibiotics, dairy products and calcium do not significantly interfere with amoxicillin absorption.
Does amoxicillin suspension need to be refrigerated?
Most amoxicillin oral suspensions should be refrigerated after reconstitution and used within 14 days. Refrigeration preserves potency and improves the taste. Shake the bottle well before each dose to redistribute the active ingredient. Discard any remaining suspension after the 14-day period or per the pharmacy label instructions.
Can I give Tylenol or ibuprofen with amoxicillin?
Yes. Acetaminophen (Tylenol) and ibuprofen (Motrin/Advil) for children 6 months and older are safe to combine with amoxicillin to manage fever or pain associated with infection. There is no clinically significant drug interaction. Use weight-based dosing for the analgesic just as for the antibiotic and avoid combination cold medicines containing the same ingredient.