Alcohol and other CNS depressants (benzodiazepines, opioids, sedating antihistamines, antipsychotics) increase sedation/respiratory depression; CYP3A4 inhibitors (ketoconazole, itraconazole, clarithromycin, ritonavir) may increase levels; CYP3A4 inducers (rifampicin, carbamazepine, phenytoin, St John’s wort) may reduce effect; caution with SSRIs/SNRIs and other sedatives; opioids increase risk of profound sedation and breathing problems