The official use of Suboxone, a brand-name of the drug buprenorphine, is to treat people who have stopped abusing opioids and are going through withdrawal.

Three inmates at the Boonville Correctional Center face felony drug charges after they received strips of a medication used to treat opioid dependence in the mail.

The inmates allegedly received envelopes on June 26 that had orange, Suboxone strips under the stamps, Missouri Department of Corrections investigator Brian Armer alleges in charging documents. Cooper County Prosecutor Eric Phelps filed charges against each of the three inmates on Friday with attempted delivery or possession of a controlled substance to a prison, a class E felony that carries a 4-year prison term.

The official use of Suboxone, a brand-name of the drug buprenorphine, is to treat people who have stopped abusing opioids and are going through withdrawal, according to the U.S. Department of Health and Human Services. Federal law classifies it as a Schedule III controlled narcotic, along with Tylenol with Codeine.

Jason Parrent, 36, allegedly received two envelopes in the mail from a woman. They contained a total of four strips under the stamps, according to court documents. Parrent is serving a 15-year sentence for voluntary manslaughter after he was convicted by a St. Francois County jury in 2012. Phelps charged Parrent with three counts of attempted delivery or possession of a controlled substance to a prison.

Travis Busse, 33, allegedly received two envelopes in the mail containing two strips under the stamps from a different woman. Busse is serving three concurrent 10-year sentences, five concurrent 5-year sentences and a 7-year sentence for felony drug, gun and forgery convictions. Phelps charged Busse with one count of felony attempted delivery or possession of a controlled substance to a prison.

Jeffery Nash, 40, allegedly received two envelopes from a third woman. They contained two Suboxone strips under the stamps. Nash is serving three consecutive 6-year sentences and one 4-year sentence for felony drug and domestic assault convictions. Phelps charged Nash with one count of felony attempted delivery or possession of a controlled substance to a prison.

None of the three women who allegedly mailed the strips to the prison has yet been charged, according to searches of online court records. Nash, Busse and Parrent are scheduled to appear before 18th Circuit Judge Keith Bail on August 27.