Threads asking if a drug is recreational are not permitted here - between google, erowid and wikipedia, this information is very easy to obtain elsewhere.
Metaxalone (brand name Skelaxin) may be marginally useful in alleviating some of the muscle pain associated with opioid withdrawal but don't expect miracles from it. There is a lot of discussion in Other Drugs regarding what is and is not useful for opioid withdrawal so check the directory link in my signature for more information and feel free to drop me a PM if you have any questions.