Specifically, the apparent extension of the duration of effect of the IR tablets (all other things being equal, oxymorphone has a duration of action of 5 to 8 hours in most patients)
versus similar drugs in commonly used immediate-release forms -- for example Dilaudid (
hydromorphone), morphine, Vilan(nicomorphine), Paramorfan (dihydromorphine) as well as prodrugs for this group such as hydrocodone, nicocodeine, codeine, dihydrocodeine and others -- is often attributed to a marginal extended-re