Penicillin G (Benzyl penicillin)

Penicillin G (Benzyl penicillin) In Dogs & Cats: Uses, Dosage and Side Effects

Overview

• It binds to penicillin-binding proteins involved in cell wall synthesis, decreasing bacterial cell wall strength and rigidity, and affecting cell division, growth and septum formation. As animal cells lack a cell wall the beta-lactam antibiotics are safe.
• Kills bacteria in a time-dependent fashion.

Uses of Penicillin G (Benzyl penicillin)

• Beta-lactamase-susceptible antimicrobial.
• Narrow spectrum of activity, susceptible to stomach acid degradation.
• Used parenterally for infections caused by sensitive organisms (e.g., Streptococcus, Clostridium, Borrelia burgdorferi, fusospirochaetes).
• Sodium salt is well absorbed from s.c. or i.m. sites.
• Procaine penicillin is sparingly soluble, providing a slow-release ‘depot.’
• Penicillin kills in a time-dependent manner; maintaining tissue concentrations above the MIC is crucial throughout the interdosing interval.
• Patients with significant renal or hepatic dysfunction may require dosage adjustment.

Dose of Penicillin G (Benzyl penicillin) in Dogs and Cats

Dogs, Cats:

• Penicillin G sodium: 15–25 mg/kg i.v., i.m. q4–6h.
• Penicillin G procaine: 30 mg/kg s.c. q24h.
• Penicillin G procaine and benzathine combined: 15 mg/kg procaine penicillin with 11.25 mg/kg benzathine penicillin equivalent to 1 ml per 10 kg body weight.

Side Effects of Penicillin G (Benzyl penicillin) in Dogs and Cats

• 600 mg of penicillin G sodium contains 1.7 mEq of Na+.
• This may be clinically important for patients with restricted sodium intakes.
• The i.m. administration of >600 mg/ml may cause discomfort.

Contraindications of Penicillin G (Benzyl penicillin) in Dogs and Cats

• Do not use in animals sensitive to beta-lactam antimicrobials.

Some Notes:

• Aminoglycosides may inactivate penicillins in vitro when mixed in parenteral solutions.
• However, they act synergistically when administered concurrently in vivo.
• Procaine can antagonize the action of sulphonamides.
• Therefore, procaine penicillin G should not be used with sulphonamides.