In-vitro interaction between dibekacin and penicillins.

Area of Science:

• Pharmacology
• Microbiology
• Medicinal Chemistry

Background:

• Aminoglycoside antibiotics like dibekacin are crucial for treating bacterial infections.
• Semi-synthetic penicillins can interact with and inactivate other antibiotics.
• Understanding these interactions is vital for safe and effective combination therapies.

Purpose of the Study:

• To investigate the in vitro inactivation kinetics of dibekacin by three semi-synthetic penicillins.
• To assess the influence of penicillin concentration and reaction medium on inactivation.
• To compare the inactivation of dibekacin and gentamicin under similar conditions.

Main Methods:

• In vitro kinetic studies were performed using dibekacin and carbenicillin, ampicillin, or ticarcillin.
• Dibekacin inactivation was measured over time at a fixed dibekacin/beta-lactam ratio (1/100).
• Experiments were conducted in buffered solutions (pH 7.4) and human serum.

Main Results:

• Ticarcillin achieved 99% dibekacin inactivation, followed by carbenicillin (90%) and ampicillin (65%) over 45 hours.
• A linear relationship was observed between the inactivation constant (Ki) and penicillin concentration for carbenicillin and ampicillin.
• Dibekacin inactivation was lower in human serum compared to buffered solutions.
• Similar inactivation degrees were observed for dibekacin and gentamicin.

Conclusions:

• Semi-synthetic penicillins, particularly ticarcillin, can significantly inactivate dibekacin in vitro.
• Penicillin concentration and the reaction medium (serum vs. buffer) influence the inactivation rate.
• These findings highlight potential drug-drug interactions relevant to clinical practice.