In vitro evaluation of ampicillin-gentamicin interactions

Area of Science:

• Pharmacology
• Microbiology
• Infectious Diseases

Background:

• Ampicillin and gentamicin are commonly used antibiotics for treating bacterial infections.
• Understanding potential drug-drug interactions is crucial for effective treatment.
• In vitro studies are essential to assess antibiotic compatibility before clinical application.

Purpose of the Study:

• To evaluate the in vitro compatibility and potential inactivation of ampicillin when combined with gentamicin.
• To determine if these antibiotics affect each other's stability under conditions simulating physiological environments.

Main Methods:

• Ampicillin (100 µg/mL) was incubated with gentamicin (10 µg/mL) in three different media: human serum, phosphate-buffered saline (0.01 mol/L, 37°C), and water (25°C).
• Antibiotic concentrations were assessed over a six-hour period.
• The study simulated peak prophylactic serum concentrations achievable in a 70-kg adult.

Main Results:

• No clinically significant inactivation of ampicillin by gentamicin was observed in any of the tested conditions.
• Both antibiotics maintained their stability in serum, saline, and water for the duration of the six-hour study.
• The observed concentrations were consistent with those expected after parenteral administration.

Conclusions:

• Ampicillin and gentamicin are compatible when combined in vitro at clinically relevant concentrations.
• This combination is unlikely to lead to significant mutual inactivation in vivo, supporting its use in prophylactic settings.
• Further in vivo studies may confirm these findings in a clinical context.