ST. LOUIS (AP) – The nation’s largest pharmacy benefit manager will soon limit the number and strength of opioid drugs prescribed to first-time users.

The move by Express Scripts is part of a wide-ranging effort to curb an epidemic affecting millions of Americans.

But the new program is drawing criticism from the American Medical Association. The organization says doctors and patients should decide the course of treatment.

Federal health officials report that an estimated 12.5 million Americans misused prescription opioids in 2015, and about 33,000 people died from overdoses.

Express Scripts wants to limit prescriptions to seven days for first-time users and require short-acting opioids. The Missouri-based company also wants to monitor for potential abuse. The program excludes hospice, palliative care and cancer patients.

A competitor, CVS Caremark, has a similar program.

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