In the human liver, Tramadol is usually converted into the much more active compound desmetramadol, by the removal of the single methyl group
. This has different affinities so different users may experience different effects.
Tramadol is a Schedule IV controlled substance in the US and only available on prescription in the UK and many other countries.
Like opiates, it may be addictive.
Primarily for this reason, it is banned in some countries, notably Egypt*, Dubai and Abu Dhabi.
*See web reference below
The World Anti-Doping Agency or WADA has officially banned Tramadol in a sports context.