Carwin was named as a past customer of Applied Pharmacy Services (APS) after a federal judge handed one of its pharmacists, J. Michael Bennett, a four-year prison term for selling anabolic steroids produced in Mobile.
Carwin had no comment, but plans to make a statement at a later date, his manager Jason Genet said when reached by MMA Fighting.
The government's case against the pharmacy, which earned convictions against five men, charged that APS shipped over 750,000 dosages of steroids to 17 different "rogue" doctors and clinics over a two-year span from Aug. 2004 to Aug. 2006. Prosecutors reportedly referred to the defendants as "drug dealers in lab coats."
Carwin was named as one of the recipients by Assistant U.S. Attorney Donna Dobbins. The 35-year-old Carwin made his mixed martial arts debut in Oct. 2005 but did not join the UFC until May 2008.
After starting his pro career with 12 straight wins, Carwin rapidly ascended the ranks of the UFC's heavyweight division, capturing the interim title in March 2010 and earning a championship match against Brock Lesnar.
Just last month, Carwin nearly won the belt, overwhelming Lesnar in the first round before falling to a second-round arm triangle submission.
Carwin has never failed a drug test in his professional fighting career.
According to AL.com, the other pro athletes referenced in court documents include baseball players, bodybuilders and pro wrestlers, most notably former WWE champion Kurt Angle. The report does not detail whether prosecutors plan to pursue legal action against any of them.
According to previous reports, a key witness in the case was a Greeley, Colorado doctor named Kenneth Olds, who admitted writing fraudulent prescriptions as part of the APS conspiracy. He eventually became a prosecution witness and received a sentence of probation. Another Greeley doctor, Dr. Kelly Wade Tucker, was sentenced to 21 months in prison for his role in the case, while a third, Dr. Scott Corliss, also pled guilty to taking part in the ring. Carwin is a resident of Greeley, though no reporting or evidence mentioned in news accounts connects him to the men.
APS was also one of the pharmacies named in The Mitchell Report, an investigation of rampant steroid use in Major League Baseball. Among the players linked to the pharmacy in the report were Jose Canseco, John Rocker, Garry Matthews Jr., and Jerry Hairston, Jr.