First-lineAmoxil
Amoxicillin
Aminopenicillin (β-lactam)
Workhorse oral penicillin — GBS prophylaxis backup, UTI, listeria cover.
OralIV
First-line for
- UTI in pregnancy (susceptible E. coli)
- GBS prophylaxis (alternative)
- Listeria cover
- Adjunct in chorioamnionitis
Mechanism
Binds penicillin-binding proteins → blocks peptidoglycan cross-linking → bacterial lysis.
“Safe penicillin, broader than benzyl”
- Gram-pos + some Gram-neg + Listeria
- Pair with clavulanate for β-lactamase producers
Dosing
- Oral
- 500 mg TDS
- IV (severe)
- 2 g q6h
Contraindications
- AbsolutePenicillin anaphylaxis
- CautionInfectious mononucleosis — rash risk
Side effects
- Rash, anaphylaxis
- Diarrhoea, candidiasis
- C. difficile (rare)
Fetal & maternal notes
- • Safe T1–T3 and lactation
- • Preferred β-lactam in pregnancy
Key interactions
Methotrexate
Avoid↑ MTX levels
Warfarin
CautionMild ↑ INR
Allopurinol
Caution↑ rash incidence
Clinical pearls
- 💡 Combine with clavulanate (co-amoxiclav) for broader Gram-neg cover
- 💡 Not active against MRSA or ESBL organisms
Content last reviewed: REPLACE_ME (e.g. 2026-07)
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