The U.S. Food and Drug Administration has approved a �usual adult dosage� on the package insert for methadone that several studies say could be deadly.
�The usual adult dosage is 2.5 mg to 10 mg every three or four hours as necessary,� reads the drug�s package insert under �For Relief of Pain.�
Someone reading that label could believe it is safe for an adult to consume up to 80 milligrams of methadone a day.
But 50 milligrams of methadone or less can kill a patient not used to strong painkillers, studies say.
�Most people would die if they took 80 milligrams a day,� said Lynn Webster, a pain doctor and researcher from Utah. �That�s an extremely dangerous, liberal guideline.�
Several other pain doctors and researchers contacted by the Sunday Gazette-Mail agreed that the dosing information potentially was dangerous.
The Gazette-Mail asked two of the biggest methadone manufacturers, Roxane Laboratories and Tyco/Mallinckrodt, about the safety of the dosing information in their package inserts.
�We really wouldn�t have a comment on that,� said Roxane spokeswoman Dawn Plante. �It�s an FDA issue.�
Tyco/Mallinckrodt spokeswoman JoAnna Schooler said in an e-mail, �The content of package inserts for pharmaceutical products like methadone is approved by the U.S. Food & Drug Administration (FDA). It serves as the official guideline for clinicians prescribing the product.
�However, the ultimate decision regarding the appropriate dosage for the patient is determined by the prescribing clinician.�
An FDA spokeswoman said agency officials are aware of the issue and are working with the drug manufacturers to change the information.
But because the drug is used to treat addictions as well as pain, agency officials didn�t want to scare off people who need the drug to kick heroin or other opioid drugs, said FDA spokeswoman Susan Cruzan.
�The Agency is working with the sponsors of the other methadone formulations, which are prescribed for and administered to pain patients, to make appropriate changes to the labeling for those products,� Cruzan said in an e-mail.
Potentially dangerous guidelines
Methadone is a long-acting medication. That means it takes a long time for patients to feel its effects and a long time to exit the body.
A toxic level of methadone can accumulate in the body before an overdose victim knows it. Often, the victim falls asleep and stops breathing. By the time anyone notices, it is too late.
Methadone is more dangerous for patients who are �opioid-naive,� who don�t ordinarily take methadone or drugs in the same family, such as heroin, morphine or fentanyl.
Until recently, opioid-naive people rarely were prescribed methadone. But it is a cheap and effective painkiller, earning it a spot on the �preferred drug� lists of insurance companies and government health plans. Doctors are prescribing it more often for pain.
As methadone sales have risen, so have the number of overdose deaths blamed on methadone. As the deaths multiply, several researchers have recommended physicians start patients on much lower doses.
A 1988 version of one medical book says that 50 milligrams of methadone in adults and 10 milligrams in children had proven fatal, according to �Medical Toxicology � Diagnosis and Treatment of Human Poisoning.�
Webster said he would prescribe no more than 20 milligrams per day to someone new to opioid drugs. Elderly or sick patients should start much lower.
In 2000, the College of Physicians and Surgeons of Ontario said to start at 7.5 milligrams per day for opioid-naive patients. A February 2006 paper published on the Web site Pain Treatment Topix, paid for by methadone-maker Tyco/Mallinckrodt, suggests no more than 5 milligrams per day for patients not accustomed to opioid drugs.
The language on the package insert isn�t the only problem, Webster said. When doctors want to switch patients from one drug to another, they often rely upon conversion tables published by the drug manufacturers.
Those tables are out of date and just plain wrong, he said. The conversion tables are designed for a single dose, not for several days or weeks of use, he said. Unlike other opioid drugs, methadone builds up in the body and is slow to leave.
�I think those conversion tables are misleading and very dangerous to use,� he said.