Penicillin For Horses

Penicillin G is a bactericidal, time-dependent β-lactam antibiotic with good activity against many Gram-positive organisms, though it is not effective against β-lactamase-producing Staphylococcus spp., α-Streptococcus spp., or Rhodococcus equi. It has limited efficacy against Gram-negative bacteria.

Penicillin G distributes widely through the plasma but has low lipid solubility and does not penetrate abscesses or sites of tissue necrosis well. The active form of penicillin G is excreted in high concentration in the urine.

Dose

Species	Usage	Dose
Horses	For susceptible infections (Sodium penicillin G, potassium penicillin G)	22,000-44,000 IU/kg IV q6h, given slowly
	For susceptible infections (Procaine penicillin G)	22,000 IU/kg IM q12h

Acceptable Uses

• First line choice for treatment of streptococcal infections such as Streptococcus equi (strangles), or Streptococcus zooepidemicus (upper and lower respiratory infection).
• Treatment of clostridial infections such as clostridial myositis, botulism, or tetanus.
• Treatment of susceptible urinary tract infections.
• When used in combination with gentamicin, a first line choice for broad-spectrum therapy (as in cases of peritonitis, pleuropneumonia, cholangiohepatitis, sepsis, or endocarditis).
• Treatment of orthopedic infections (osteomyelitis, septic arthritis) when β-lactamase-producing Staphylococcus spp. or Enterobacteriaceae have been ruled out by culture.

Unacceptable Uses

• Treatment of suspected or cultured-confirmed Enterobacteriaceae infections.
• Inactivated in the presence of purulent or necrotic material (e.g. abscesses).
• Empirical treatment of suspected staphylococcal infections.
• In combination with a bacteriostatic antimicrobial, efficacy is decreased.

Formulations Available within the OSU Pharmacy

• Penicillin gel 5ml/syringe
• Penicillin gel 10ml/syringe
• Penicillin G Potassium 20mmu injectable suspension
• Penicillin G Procaine injectable suspension (1 ml, 30 ml, 100 ml, 250 ml)