NEW YORK (AP) — A doctor at a New York City pain clinic has pleaded not guilty to manslaughter charges alleging he caused the fatal overdose of two patients.

Stan Li was released on $750,000 bond after entering the plea in state court on Thursday.

Authorities said previously that Li provided 24 prescriptions filled by David Laffer, who killed four people in a 2011 Long Island pharmacy robbery.

Li, who lives in Hamilton, N.J., operated a pain management clinic in Queens. The indictment accuses the 58-year-old physician of prescribing lethal amounts of highly addictive prescription medications to two men who overdosed. The drugs included oxycodone and Xanax.

Li faces up to 15 years in prison if convicted.

Laffer is serving a life sentence for the pharmacy killings.