Benzylpenicillin Potassium

Jekl, V., et al. Vet Rec, 2016, 179(1), 18.

Benzylpenicillin potassium (penicillin G) is a "narrow spectrum" penicillin with specific activity against Gram-positive aerobics, facultative aerobes, and obligate anaerobes. In rabbits, penicillin G is recommended for the treatment of pasteurellosis, odontogenic abscesses, and treponematoses. The aim of this work was to determine the pharmacokinetic concentrations of benzylpenicillin potassium in rabbit plasma samples after a single intramuscular injection of 38 mg/kg body weight (BW) and to recommend an optimal dosing interval.
The main findings of this study showed that after a single intramuscular administration, the mean Benzylpenicillin potassium concentration reached a maximum concentration (9.5 mg/ml) within 36 minutes. At 9 and 12 hours, the Benzylpenicillin plasma values decreased to 0.32 and 0.13 mg/ml, respectively.
Due to the short terminal half-life of benzylpenicillin, it is essential to sustain the therapeutic plasma concentration, necessitating frequent dosing. Administering doses every 12 hours would achieve plasma levels exceeding 0.1 mg/ml in most rabbits; however, this may be inadequate for combating pathogens with high minimum inhibitory concentrations (MICs).

Nakamura, Tomomi, et al. Journal of Infection and Chemotherapy, 2018, 24(10), 856-859.

This work investigated the stability of antimicrobial agents (β-lactam antibiotics such as benzylpenicillin potassium and ampicillin) in five different infusion solutions in a clinical setting.
· Evaluation Methods
Benzylpenicillin potassium (PCG) and ampicillin (ABPC) were dissolved in five different infusion solutions and stored at 25 or 31.1 °C for 24 h. The five infusion solutions were: Ringer's acetate, saline solution, 5% dextrose solution, dextrose electrolyte solution without potassium, and dextrose electrolyte solution with potassium. The residual rate was determined by high-performance liquid chromatography (HPLC).
· Results
Dissolved PCG in acetate Ringer's solution remained stable for 24 hours at temperatures of 25 °C and 31.1 °C, showing percentages of 101.7 ± 1.4% and 92.9 ± 1.3%, respectively. Additionally, the PCG solution did not adhere to the elastomeric infusion pump after 24 hours at 31.1 °C. When stored in an elastomeric infusion pump at 4 °C, the PCG solution maintained stability for 10 days, displaying a stability percentage of 99.7 ± 0.5%. In contrast, ABPC proved unstable across all tested infusion solutions and temperatures. These findings suggest that PCG in acetate Ringer's solution is suitable for use in outpatient parenteral antimicrobial therapy (OPAT) with continuous infusion pumps.