Common Antibiotics

Always follow local formulary (e.g. SEL/BNF/BNFC/NICE). Adjust for renal function. Consider allergy, pregnancy, safety-netting, and delayed prescriptions when appropriate.

Antibiotic Classification by Type

🧪 Penicillins

  • Amoxicillin
  • Ampicillin
  • Flucloxacillin
  • Co-amoxiclav
  • Phenoxymethylpenicillin
  • Benzylpenicillin
  • Piperacillin (Tazocin)
  • Ticarcillin

🦠 Cephalosporins

  • Cefalexin
  • Cefuroxime
  • Ceftriaxone
  • Cefotaxime
  • Cefaclor
  • Cefpodoxime
  • Ceftazidime
  • Cefepime

🔬 Tetracyclines

  • Doxycycline
  • Tetracycline
  • Minocycline
  • Oxytetracycline

📡 Macrolides

  • Clarithromycin
  • Erythromycin
  • Azithromycin

🧫 Fluoroquinolones

  • Ciprofloxacin
  • Levofloxacin
  • Moxifloxacin
  • Ofloxacin

🧴 Aminoglycosides

  • Gentamicin
  • Amikacin
  • Tobramycin
  • Neomycin
 

Antibiotic Use in Penicillin Allergy

❌ Contraindicated

These antibiotics must be avoided in confirmed penicillin allergy, including anaphylaxis, angioedema, or severe rash.

  • Amoxicillin
  • Ampicillin
  • Flucloxacillin
  • Pen V
  • Piperacillin (incl. Tazocin)
  • Ticarcillin
  • Co-amoxiclav
  • Co-fluampicil

⚠️ Use with Caution

May be used in mild non-anaphylactic allergy (e.g. minor rash). Avoid in severe allergy.

Cephalosporins:
  • Cefalexin
  • Cefuroxime
  • Cefaclor
  • Cefotaxime
  • Ceftriaxone
  • Cefpodoxime
Other beta-lactams:
  • Aztreonam
  • Meropenem
  • Imipenem
  • Ertapenem

✅ Considered Safe

These antibiotics are not structurally related to penicillin and are generally safe in penicillin allergy.

  • Clarithromycin
  • Erythromycin
  • Azithromycin
  • Metronidazole
  • Doxycycline
  • Linezolid
  • Gentamicin
  • Ciprofloxacin
  • Trimethoprim
  • Vancomycin
  • Teicoplanin
  • Chloramphenicol
 

Primary Care Antibiotics - Adult & Paediatric Quick Reference

Penicillins

  • Amoxicillin:
    • Adults: 500 mg TDS (typical)
    • Children: 40-90 mg/kg/day in 3 divided doses (max 1 g TDS) make sure you follow BNFC guideline
  • Phenoxymethylpenicillin:
    • Adults: 500 mg QDS
    • Children: 12.5-25 mg/kg BD-QDS (max 1 g/day)
  • Flucloxacillin:
    • Adults: 500 mg QDS
    • Children: 12.5-25 mg/kg QDS (max 1 g QDS)

Macrolides

  • Clarithromycin:
    • Adults: 250-500 mg BD
    • Children: 7.5 mg/kg BD (max 500 mg BD)
  • Erythromycin: (preferred in pregnancy)
    • Adults: 250-500 mg QDS
    • Children: 10-15 mg/kg QDS

Tetracyclines

  • Doxycycline:
    • Adults: 200 mg STAT then 100 mg OD
    • Children: contraindicated if under 12 years

UTI Agents

  • Nitrofurantoin:
    • Adults: 100 mg MR BD (or 50 mg QDS)
    • Children: 750 mcg/kg QDS (check renal function)
  • Trimethoprim:
    • Adults: 200 mg BD
    • Children: 4 mg/kg BD (check folate/BMS)
References:
- NICE CKS Antibiotic Guidance (2023)
- BNF & BNFc – Antimicrobial Dosing
- SEL ICS Primary Care Antibiotics Formulary
- UKHSA TARGET Antibiotic Toolkit
 

Secondary Care Antibiotics - Quick Reference for PAs

Key IV Antibiotics in Acute Settings

  • Co-amoxiclav IV: 1.2 g TDS - broad-spectrum, good for abdominal, ENT, mixed infections
  • Piperacillin-Tazobactam (Tazocin): 4.5 g TDS/QDS - severe sepsis, pyelonephritis, neutropenic fever
  • Ceftriaxone: 1-2 g OD > CAP, meningitis, gonorrhoea
  • Vancomycin IV: For MRSA, line sepsis > weight-based dosing + TDM
  • Meropenem: 1 g TDS - reserved for resistant organisms/ICU
  • Gentamicin: Single daily dose (check renal function + TDM)

Common Step-Down Oral Agents

  • Co-amoxiclav : 500/125 mg TDS
  • Cefalexin: 500 mg QDS or BD - UTI, cellulitis
  • Clarithromycin: 500 mg BD - for atypicals or penicillin allergy
  • Doxycycline: 200 mg STAT then 100 mg OD - CAP, skin/soft tissue
  • Trimethoprim or Nitrofurantoin: for UTIs if organism is sensitive

Monitoring & Safety Considerations

  • Gentamicin: requires trough/peak monitoring, avoid in AKI
  • Vancomycin: adjust for renal impairment
  • Check allergies: especially penicillin or beta-lactam cross-reactivity
  • De-escalate or IV-to-oral switch after 48-72 hrs if stable and improving

Escalate or Refer When...

  • No response to antibiotics within 48-72 hours
  • Suspected source control issue (e.g. abscess, infected line)
  • Positive blood cultures (bacteraemia)
  • Unusual pathogens or resistance (ESBL, MRSA, Pseudomonas)
  • Neutropenic sepsis, ICU patients, meningitis, endocarditis → involve microbiology/infectious diseases early
References:
- NICE NG15 & NG51: Sepsis and HAP
- UKHSA & PHE Secondary Care Antibiotic Guidance
- South East London AMS IV-to-Oral Switch Guide
- BNF (IV dosing and renal adjustment)