Benzylpenicillin (Penicillin G)

Last updated 23/12/17

Definition

• Parenteral injectible penicillin

Features

• Beta lactam class of antibiotics
• Standard formulation intravenous or intramuscular (IMI)
• Available in 2 longer acting IMI formulations which get metabolised to Benzylpenicilin
• Procaine Benzylpenicillin
• Benzathine Benzylpenicillin (LA Bicillin): longest acting
• Inactivated by bacerial beta lactamases
• Renal excretion
• Poor Cerebrospinal Fluid (CSF) penetration

Mechanism

• Bacteriocidal
• Inhibits cell wall synthesis

Indications

• Presentations
• Meningitis: empirical cover
• Pneumonia
• Community Acquired Pneumonia (CAP)
• Aspiration pneumonia
• Syphilis
• Leptospirosis
• Tetanus
• Sepsis in children
• Prophylaxis
• Infective Endocarditis (IE)
• Splenectomy
• Bacterial Coverage
• Gram Positives
• Streptococci
• Streptococcus pyogenes
• Streptococcus pneumoniae
• Streptococcus viridans
• Streptococcus agalactiae (GBS)
• Staphylcocci
• Clostridium difficile
• Gram Negatives
• Cocci
• Neisseria
• Spirochetes
• Treponema pallidum
• Leptospira
• Actinomyces bovis
• Streptobacillis moniliformis
• Listeria monocytogenes
• Bacilus anthracis
• Cornybacterium diptheria
• Benzathine Benzylpinicillin IM
• Syphilis, Yaws, Bejel, Pinta
• Prophylaxis for Acute Rheumatic Fever (ARF) and Rheumatic Heart Disease (RHD)
• Procaine Benzylpenicillin
• CAP
• Syphilis (Benzathine preferred)
• Cellulitis, erysipelas

Dose

• IV or IM
• Ampules
• Benzylpenicillin: 600mg, 1.2g or 3g
• 600mg = 1 million units
• White powder reconstituted with water for injection
• Procaine Benzylpenicillin: 1.5g syringe
• 1g = 1 million units
• Benzathine Benzylpenicillin: 900mg syringe
• 1.8g = 2.4 million units
• Dose
• Benzylpenicillin
• Adult: 1.2-2.4g IV 4-6 hourly
• Paeds: 30-50mg/kg IV 6 hourly
• Procaine Benzylpenicillin: duration 12-24hrs
• Adult: 1-1.5g IM Daily
• Paeds: 50mg/kg IM Daily
• Benzathine Benzylpenicillin: duration 2-4 weeks
• Adult >20kg: 900mg-1.8g STAT or 3-4 weekly
• Paeds <20kg: 450mg STAT or 3-4 weekly
• Frequency of dosing
• Benzylpenicillin IV/IM 4-6 hourly
• Procaine Benzylpenicillin IM daily dosing
• Benzathine Benzylpenicillin IM 3-4 weekly dosing

Side Effects/Precuations/Contraindications

• Side Effects
• Anaphylaxis
• More likely in patients with allergic propensity and IV administration
• Pruritic rash
• Clostridium Difficile Assoacited Diarrhoea (CDAD)
• Jarisch-Herxheimer in spirochete infections
• Benzathine IMIs are more painful than Procaine
• Pain may be sufficient that patients avoid subsequent doses
• Precautions
• Cephalosporin anaphylaxis
• Probenecid blocks renal tubular secretion
• Pregnancy: A
• Lactation: best avoided to prevent sensitisation
• Contraindications
• Penicillin anaphylaxis

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References

1. AMH: Procaine Penicillin. July 2017.
2. AMH: Benzathine Penicillin. July 2017.
3. MIMMS Online: Benzylpenicillin. 2017