Amoxicillin
Amimox · Amoxicillin Sandoz · Amoxicillin Teva
Aminopenicillin that covers Haemophilus influenzae in addition to pneumococci — and it is that difference from phenoxymethylpenicillin that determines its use. Amoxicillin is therefore not first-line for uncomplicated acute otitis media — that role belongs to phenoxymethylpenicillin — but for treatment failure, recurrent otitis, otitis with concurrent purulent conjunctivitis, and as a suspension alternative in pneumonia in young children. Oral bioavailability is substantially better than phenoxymethylpenicillin and is not affected by food.
Do not give amoxicillin for sore throat when infectious mononucleosis is suspected. Almost all patients with EBV infection develop a widespread maculopapular rash, which is frequently and incorrectly documented as lifelong penicillin allergy and thereafter shapes the patient's antibiotic choices for decades.
Dosing in adults
| Indication | Regimen | Comment |
|---|---|---|
| Acute otitis media, treatment failure or recurrence | Children 20 mg/kg × 3 orally for 10 days; adults 750 mg × 3 for 10 days | first-line only at this point — phenoxymethylpenicillin first otherwise |
| Otitis with purulent conjunctivitis | Children 20 mg/kg × 3 orally for 5–10 days | the syndrome points to Haemophilus influenzae |
| Pneumonia in children | 15 mg/kg × 3 orally for 5 days | equivalent alternative to phenoxymethylpenicillin, practical as suspension |
| Lyme disease (erythema migrans) in children under 8 years and in pregnancy | Children 15 mg/kg × 3 orally for 10 days; adults 500 mg × 3 for 10 days | replaces doxycycline in these groups |
| Helicobacter pylori eradication | 1 g × 2 orally for 7–14 days with PPI and clarithromycin or metronidazole | always in combination, never as monotherapy |
eGFR 10–30 ml/min: extend dosing interval to × 2. eGFR below 10 ml/min: × 1, and avoid the highest doses. Dialysed — give dose after dialysis.
No routine dose adjustment. Monitor liver tests in known liver disease and in treatment longer than 10 days.
15 mg/kg × 3 for pneumonia, 20 mg/kg × 3 for otitis. Maximum daily dose usually 60 mg/kg. Available as granules for oral suspension 50 and 100 mg/ml, which is the practical advantage over phenoxymethylpenicillin in young children.
Avoid for non-specific sore throat until mononucleosis is excluded, and avoid as a routine substitute for phenoxymethylpenicillin in first-episode otitis or pneumococcal pneumonia — the broader spectrum provides no clinical benefit but drives both resistance and diarrhoea. In suspected beta-lactamase-producing Haemophilus, amoxicillin-clavulanate is required, not amoxicillin alone.
Pharmacokinetics
- BIOAVAIL.
- approximately 80 % orally
- t½
- 1–1,5 hours
- PROTEIN BINDING
- approximately 20 %
- METABOLISM
- Minimal
- EXCRETION
- Renal, 60 % unchanged in urine
- FOOD EFFECT
- No clinically significant effect
- PK/PD INDEX
- T > MIC
- ONSET
- Peak serum concentration after 1–2 hours