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Penicillin G (parenteral)

Benzylpenicillin sodium

Brand names: Crystapen

Adult dose

Dose: 1.2–2.4g IV q4–6h (severe infection); meningococcal sepsis pre-hospital: 1.2g IM/IV
Route: IV / IM
Frequency: q4–6h

Clinical pearls

  • NICE NG52 / UKHSA: meningococcal sepsis pre-hospital
  • BNF/JFC: streptococcal infections, syphilis (alternative to benzathine)
  • BSAC / UKHSA AMR — narrow-spectrum

Contraindications

  • Penicillin hypersensitivity

Side effects

  • Hypersensitivity / anaphylaxis
  • Diarrhoea / C. difficile
  • Jarisch-Herxheimer (syphilis)
  • Encephalopathy (high-dose, renal impairment)
  • Haemolytic anaemia (rare)

Interactions

  • Probenecid
  • Methotrexate
  • Anticoagulants (rare)

Monitoring

  • Renal function
  • C. diff
  • Resolution

Reference: BNF; NICE NG52; UKHSA; BSAC; https://bnf.nice.org.uk/drugs/benzylpenicillin-sodium/. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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