ROANOKE, Va. (AP) — A former Virginia doctor has been sentenced to three years in prison for writing prescriptions that mixed powerful painkillers into narcotic cocktails that killed at least four of her patients, officials said,

Verna M. Lewis, 70, pleaded guilty last year to dispensing controlled substances — oxycodone, morphine and hyrdomorphone — without a legitimate medical purpose, The Roanoke Times reported. As part of her sentence, Lewis was fined $10,000 and agreed never to practice medicine again.

Court records said Lewis grossed about $523,000 from illegal prescriptions over a two-year period that ended in March 2019. The doctor, who surrendered her medical license and retired shortly after drug agents raided her practice later that year, has since paid a $500,000 forfeiture to the federal government.

Lewis, who ran a rehabilitation and pain management practice, was not held criminally responsible for the accidental overdoses. Autopsies found they were caused by a combination of the prescriptions and illegal street drugs or over-the-counter medications her patients obtained elsewhere.

Lewis, who was sentenced on Monday. She called the case “one of my deepest regrets.”