Because the cheap synthetic form of opium has sometimes been abused by users or poorly prescribed by doctors, methadone is now involved in more than twice as many deaths as heroin, The New York Times reported Sunday.

"This is a wonderful medicine used appropriately, but an unforgiving medicine used inappropriately," said Dr. Howard A. Heit, a pain specialist at Georgetown University. "Many legitimate patients, following the direction of the doctor, have run into trouble with methadone, including death."

Deaths with methadone as a contributing factor increased nearly five times between 1999 and 2005, to 4,462, a number that may be an underestimate since states do not always specify the nature of drug overdoses, The Times said.