Co-detection of a benzodiazepine and an opioid does not identify the mechanism or magnitude of their interaction.
The supplied review considered new synthetic opioids alongside benzodiazepines and other co-exposures. It distinguished pharmacodynamic interactions, involving combined physiological effects, from pharmacokinetic interactions that change absorption, metabolism or elimination. The literature included reports of mixed intoxication as well as mechanistic information.
A mixed-intoxication report does not isolate the contribution of each substance. Evidence for one opioid cannot automatically be assigned to every analog. The review is historical and does not establish the composition of a current illicit product or a universal potency hierarchy.
For a forensic opinion, identify each confirmed substance, its specimen, timing and relevant mechanism. A plausible combined depressant effect and a documented change in concentration are different propositions. Explain which is supported instead of treating the phrase drug interaction as a complete causal account.
Source: Publication PMC6193107, read from the supplied PDF. Applications to expert analysis are interpretation.
Related reading: A Synthetic Cannabinoid Enhanced Clonazepam but Not Clobazam in One Mouse Seizure Model.