Dependence liability of Tramadol.

Some controversy exists regarding the dependence liability of tramadol. Grünenthal has promoted it as an opioid with a low risk of dependence compared to traditional opioids, claiming little evidence of such dependence in clinical trials. They offer the theory that since the M1 metabolite is the principal agonist at μ-opioid receptors, the delayed agonist activity reduces dependence liability. The nor adrenaline reuptake effects may also play a role in reducing dependence.

Despite these claims it is apparent, in community practice that dependence to this agent does occur. This would be expected since analgesic and dependence effects are mediated by the same μ-opioid receptor. However, this dependence liability is considered relatively low by health authorities, such that tramadol is classified as a Schedule 4 Prescription Only Medicine in Australia, rather than as a Schedule 8 Controlled Drug like other opioids (Rossi, 2004). Similarly, tramadol is not currently scheduled by the U.S. DEA, unlike other opioid analgesics. Nevertheless, the Prescribing Information for Ultram warns that tramadol "may induce psychological and physical dependence of the morphine-type."