Acetaminophen-tramadol Hydrochloride

Tramadol (Ultram, Tramal (see below)) is a centrally-acting analgesic, used for treating moderate to moderately severe pain.

Tramadol was developed by the German pharmaceutical company Grünenthal GmbH in the late 1970s.

Tramadol possesses agonist actions at the μ-opioid receptor and affects reuptake at the noradrenergic and serotonergic systems. Tramadol is a compound with mild and delayed μ-agonist activity.

Tramadol is a synthetic stripped-down piperidine-analog of the phenantherane alkaloid Codeine and, as such, is an Opioid and also a pro-drug (Codeine is metabolized to Morphine, Tramadol is converted to M-1 aka O-desmethyltramadol). Opioids are chemical compounds which act upon one or more of the human opiate receptors (the euphoria, addictive nature and respiratory depression are mainly caused by the Mu(μ) 1 and 2 receptor. The opioid agonistic effect of Tramadol and its major metabolite(s) are almost exclusively mediated by the substance’s action at the μ-receptor. This characteristic distinguishes Tramadol from many other substances (including Morphine) of the opioid drug class, which generally do not possess Tramadol’s degree of subtype selectivity.

Source: http://en.wikipedia.org/wiki/Tramadol