PPIG and respiratory depression: Hydromorphone is converted to hydromorphone 3-glucuronide (H3G) and dihydromorphine 3-glucuronide by hepatic glucuronide without being metabolized by the cytochrome P450 (CYP) system, avoiding interactions with drugs metabolized by CYP and producing no metabolites of morphine: morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G), thus reducing the incidence of renal impairment and adverse effects such as respiratory depression [2].