The main advantage of this drug is that it has a fast onset of action when taken orally, and has a high bioavailability which means that oral dosing produces almost as much effect as injection. It also has a relatively low tendency to cause constipation which is a common problem with opioid analgesics used for cancer pain relief, and tolerance to the analgesic effects develops relatively slowly compared to most other short-acting opioids.
Dextromoramide
Dicycloverine
Difelikefalin
Quadrosilan
Doxylamine
Aceclidine
Fenpentadiol
Bethanechol