Most Schedule II opioids are prescribed by general practitioners, according to a study by Stanford University published in JAMA Internal Medicine. This goes against the belief that addicts receive these drugs from illegitimate sources. Schedule II opioids are drugs that are approved by the FDA but have a high potential of abuse. The most common Schedule II drugs are codeine, hydrocodone and fentanyl.

In 2013, 15.4 million prescriptions were written for Schedule II opioids by family practice doctors. Internal medicine doctors wrote 12.8 million prescriptions, followed by nurse practitioners with 4.1 million and physicians assistants with 3.1 million. The top 10 percent of these prescribers also account for 63 percent of all prescriptions. These results came from The Centers for Medicare and Medicaid Services, which includes all prescribers and Medicare drug coverage claims in 2013. There were 808,020 prescribers and 1.18 billion claims.

General practitioners can easily overlook addiction signs in cases of chronic pain and dependence and doctor shopping.