Light heavyweight James Irvin (Pictures) admitted to allegations of painkiller use prior to his July 19 UFC bout with Anderson Silva (Pictures) in a letter received by the Nevada State Athletic Commission Monday. Irvin said he took the medication without a prescription.

The Sacramento native tested positive for the non-approved analgesic painkillers methadone and oxymorphone, according to a post-fight urinalysis collected after his TKO loss to UFC middleweight champion Silva.

Irvin lasted just over a minute with the stealth Brazilian fighter during their 205-pound contest broadcasted live on Spike TV.

“In the days leading up to my fight with Anderson Silva (Pictures), I experienced some residual pain in my foot from a previous injury,” wrote Irvin in an Aug. 14 letter. “I made the extremely poor choice to take some pain medications that I did not have a prescription for. I realize this was an ignorant and dangerous decision.”

Irvin, 29, accepted the bout with Silva only days after re-entering the gym following a six-week recovery period from a broken foot. Irvin had sustained the injury last May in preparation for a proposed co-event bout against “The Ultimate Fighter 2” winner Rashad Evans (Pictures) at UFC 85 “Bedlam,” which was held on June 7 in London.

Irvin was temporarily suspended by the NSAC on Aug. 12 pending a separate disciplinary hearing that has yet to scheduled. Irvin plans to address the five-board commission in person. NSAC-administered suspensions for non-approved drugs or stimulants (apart from steroids) have ranged from six to nine months on average. Irvin also faces a potential fine, which would constitute a percentage of the 20,000 dollar purse paid in his loss to Silva.

Mike Roberts, Irvin’s manager, said a public statement from his client is forthcoming.