Aminopenicillin (beta-lactam) antibiotic
Amoxicillin
Binds penicillin-binding proteins and inhibits peptidoglycan cross-linking, producing bactericidal cell-wall lysis in susceptible organisms.
Brands
Amoxil · Novamox · Mox
Adult dosing
Maximum 6 g/day intravenously in adults| Indication | Dose | Route | Frequency |
|---|---|---|---|
| Community-acquired pneumonia, low severity | 500 mg-1 g | Oral | Three times daily for 5 days |
| Acute otitis media / sinusitis | 500 mg | Oral | Three times daily for 5-7 days |
| Severe infection | 1 gMax 6 g/day | IV | Every 6-8 hours |
| Helicobacter pylori eradication | 1 g | Oral | Twice daily for 7-14 days |
Weight-based: Children are dosed strictly by weight up to the adult ceiling.
Paediatric dosing
Always confirm the weight and the local paediatric formulary| Indication | Dose | Route | Frequency |
|---|---|---|---|
| Pneumonia / general infection | 40-50 mg/kg/dayMax Adult dose | Oral | Divided every 8 hours |
| Acute otitis media (high dose) | 80-90 mg/kg/dayMax 4 g/day | Oral | Divided every 12 hours |
| Neonate under 7 days | 50 mg/kg/day | IV | Divided every 12 hours |
Renal adjustment
Move the slider to the patient's eGFRNo adjustment
- eGFR > 30No adjustment
- eGFR 10-30500 mg every 12 hours
- eGFR < 10500 mg every 24 hours
- Haemodialysis500 mg every 24 hours plus a dose after dialysis
Hepatic adjustment
- All gradesNo adjustment; monitor liver enzymes with prolonged therapy
Practical notes
The things that go wrong at the bedside- Take the oral dose with or without food; spacing doses evenly matters more than food timing.
- High-dose regimens are used where pneumococcal resistance is prevalent.
DrZep structured dosing table (demo dataset, formulary-aligned) · DrZep. Confirm every dose against your local formulary and the patient's weight, renal function and comorbidities.
Indications
- Community-acquired pneumonia (first line in many national guidelines)
- Acute otitis media and bacterial sinusitis
- Streptococcal pharyngitis
- Urinary tract infection when susceptibility is confirmed
- Helicobacter pylori eradication regimens
- Endocarditis prophylaxis in selected dental procedures
Dosing summary
- CAP (adult, low severity)
- 500 mg-1 g three times daily for 5 days
- Otitis media (adult)
- 500 mg three times daily for 5-7 days
- Children
- 40-90 mg/kg/day divided in 2-3 doses depending on indication
- H. pylori
- 1 g twice daily as part of triple or quadruple therapy
Organ adjustment
Renal
- eGFR 10-30
- Maximum 500 mg twice daily
- eGFR < 10
- 500 mg once daily
- Haemodialysis
- Dose after dialysis; 500 mg once daily
Hepatic
- All grades
- No routine adjustment; monitor liver enzymes with prolonged therapy
Monitoring
- 1Clinical response by 48-72 h
- 2Rash and hypersensitivity
- 3Renal function in prolonged or high-dose therapy
Contraindications & cautions
Do not use / use with care
- Penicillin hypersensitivity or previous anaphylaxis to any beta-lactam
- History of amoxicillin-associated cholestatic jaundice
Pregnancy & lactation
- Pregnancy
- Considered safe across all trimesters; a first-line antibiotic choice in pregnancy.
- Lactation
- Compatible; small amounts in milk may rarely cause infant diarrhoea or rash.
Interactions
- MethotrexateReduced renal excretion and methotrexate toxicitymajor
- AllopurinolHigher incidence of rashmoderate
- WarfarinPossible INR elevation via gut flora changemoderate
- Combined oral contraceptivesTheoretical reduced efficacy with diarrhoea or vomitingminor
Adverse effects
Common
- Diarrhoea
- Nausea
- Rash
- Oral or vaginal candidiasis
Serious
- Anaphylaxis
- Clostridioides difficile colitis
- Cholestatic hepatitis
- Stevens-Johnson syndrome
- Interstitial nephritis
Toxicity & overdose
Recognise and treat
- Overdose usually benign; crystalluria and renal impairment possible with very high doses — maintain hydration
Alternatives
- Doxycycline or a macrolide in penicillin allergy
- Co-amoxiclav for beta-lactamase producers
- Cefuroxime where a beta-lactam is still appropriate
Linked diseases & guidelines
Demo monograph for educational use. Always confirm dose, route and interactions against your national formulary and the product label before prescribing.
Demo content. Educational decision support only. Verify every dose, citation and recommendation against your national formulary and the primary source before clinical use.