Benzylpenicillin

Benzylpenicillin - can only be given parenterally. It is active against most streptococci but the majority of strains of Staphylococcus aureus are resistant due to penicillinase production. Resistance rates are increasing in Streptococcus pneumoniae, and benzylpenicillin should probably not be used for empiric treatment of meningitis unless local levels of resistance are extremely low. All strains of Neisseria meningitidis remain sensitive.

Uses:
• Infective endocarditis
• Streptococcal infections including severe necrotising soft tissue infections and severe pharyngeal infections
• Pneumococcal infections – excluding empiric therapy of meningitis
• Gas gangrene and prophylaxis in limb amputation
• Meningococcal meningitis with sensitive organism
• Tetanus
• Post-splenectomy prophylaxis

Contraindications:
Penicillin hypersensitivity

Administration:
IV: 600–1200 mg diluted in 10 ml WFI, 6 hourly over 3–5 min, higher doses should be given for severe infections in 100 ml of glucose 5% or sodium chloride 0.9% and given over 30–60 min
Infective endocarditis: 7.2 g/24 h (with gentamicin)
Adult meningitis: 14.4 g/24 h
Post-splenectomy prophylaxis: 600 mg 12 hourly
Give at a rate not >300 mg/min

In renal impairment:

CC (ml/min)	Dose (range depending on severity of infection)
10–20	600 mg–2.4 g every 6 hours
<10	600 mg–1.2 g every 6 hours

How not to use benzylpenicillin:
Not for intrathecal use (encephalopathy)
Do not mix in the same syringe with an aminoglycoside (efficacy of aminoglycoside reduced)

Adverse effects:
Hypersensitivity
Haemolytic anaemia
Transient neutropenia and thrombocytopenia
Convulsions (high-dose or renal failure)

Cautions:
Anaphylactic reactions frequent (1:100 000)
Severe renal impairment (reduce dose, high doses may cause convulsions)

Renal replacement therapy:
CVVH dose as for CC 10–20 ml/min (600 mg–2.4 g every 6 hours depending on severity of infection). Not significantly cleared by PD or HD, dose as if CC < 10 ml/min (600 mg–2.4 g every 6 hours depending on severity of infection).