The interaction between VPA and carbapenem antibiotics caused decreases in the VPA serum concentrations; the extent of this decrease was greater in the meropenem-treated patients than in the imipenem-treated or ertapenem-treated cases. Because the therapeutic effect of VPA depends on its serum concentration, it should be recognized that there may be a loss of seizure control in patients using VPA with carbapenem antibiotics.

Vancomycin trough concentrations over 12.1 mg/L were associated with an increased risk of nephrotoxicity. This is lower than the known threshold. Trough vancomycin concentration over the threshold was the only risk factor of nephrotoxicity among demographic factors, dosing regimen, and other clinical conditions in this study. It is suggested that vancomycin trough concentrations greater than 12.1 mg/L require close monitoring for nephrotoxicity.