A rat experiment found worsened blood-gas changes when oxycodone and diazepam were administered together.
The investigators first studied several doses of each drug. Oxycodone produced dose-related reductions in arterial oxygen partial pressure and increases in carbon dioxide partial pressure. Diazepam alone produced similar changes at its highest tested dose. Combining oxycodone 150 mg/kg with diazepam 20 mg/kg produced further changes consistent with exacerbated respiratory depression.
The experiment supports a model for detecting respiratory interactions using physiological measurements. Rat doses, experimental conditions, and pharmacokinetics cannot be converted directly into a human impairment threshold or fatal concentration. It also does not establish how much of an interaction in a particular patient would arise from altered exposure versus pharmacodynamic effects. In an individual case, drug timing, measured concentrations, respiratory observations, other depressants, and disease remain necessary to assess causation. The paper provides mechanistic evidence rather than a numerical rule for human outcomes.
Original analysis of the supplied journal article, identified as PMC6994827.