Concomitant use of OXAYDO with a CYP3A4 inhibitor, such as macrolide antibiotics (., erythromycin), azole-antifungal agents (., ketoconazole), and protease inhibitors (., ritonavir), may increase plasma concentrations of oxycodone and prolong opioid adverse reactions, which may cause potentially fatal respiratory depression, particularly when an inhibitor is added after a stable dose of OXAYDO is achieved. Similarly, discontinuation of a CYP3A4 inducer, such as rifampin, carbamazepine, and phenytoin, in OXAYDO-treated patients may increase oxycodone plasma concentrations and prolong opioid adverse reactions. When using OXAYDO with CYP3A4 inhibitors or discontinuing CYP3A4 inducers in OXAYDO-treated patients, monitor patients closely at frequent intervals and consider dosage reduction of OXAYDO until stable drug effects are achieved.
Whether concomitant drug abuse leads to an increased number of deaths was scientifically analysed in Sheffield, UK.  The researchers wanted to find out whether concomitant drug abuse (. an opiate plus another drug of misuse) leads to an increased number of acute accidental opiate-related deaths. The authors showed that at least in the Sheffield area, intravenous (IV) administration of an opiate is the most consistent factor associated with drug abuse deaths. The co-administration of a concomitant drug of misuse appeared to be a feature rather than a risk factor per se in such deaths.