OxyContin patent expires, fears of abuse return

The November 2011 expiration of Pfizer's patent on the cholesterol drug Lipitor and Ranbaxy Labs' release of the generic version received significant play in the media, particularly due to the theretofore status of Lipitor (atorvastatin calcium) as the drug with the highest sales in the country, $7.7 billion in the United States, according to healthcare analytics firm IMS Health.

The April 16 expiration of the patent for OxyContin (oxycodone extended-release tablets) got plenty of attention as well, not because of sky-high sales — with $3 billion in sales per year, according to IMS — but because of the controversy surrounding generic versions of the drug.

Following its 1995 approval by the Food and Drug Administration, the opioid painkiller OxyContin soon became a favorite target for drug abuse, so much so that the Drug Enforcement Administration lists it as a Schedule II controlled substance. According to the Substance Abuse and Mental Health Services Administration, about half a million people ages 12 years and older began abusing OxyContin in 2008. With abuse came crime, and OxyContin has been a prize frequently sought after in pharmacy robberies and other drug thefts.

In response, in April 2010, the FDA approved a new version of the drug that contained properties designed to deter abuse. Before, drug users would crush or dissolve the pills for snorting or injection, but the new version rendered the drug largely useless after tampering. Purdue stopped shipping the original version without the abuse-deterrent features in August 2010. Authorities have warned that the newer pills still have the potential for abuse, but that potential is reduced.

But with the expiration of OxyContin's patent came renewed fears of a prescription painkiller abuse epidemic, particularly because the agency had not yet specifically said it would require generic versions of the drug to be abuse-deterrent. In January, the FDA released draft guidance for drug companies to encourage abuse-deterrent painkillers. The guidance explains the agency's current thinking about the studies it said companies should conduct to demonstrate that a given formulation of an opioid drug has abuse-deterrent properties, how the agency would evaluate the studies and what labeling claims may be approved. But the draft guidance contained guidelines, not requirements, and that did not allay fears about the abuse potential. In a March 12 letter to FDA commissioner Margaret Hamburg, the attorneys general of 46 states, as well as Puerto Rico and Guam, urged the agency to require generic versions of OxyContin to carry the same features as the branded version.

Finally, the same day OxyContin's patent expired, the FDA announced that it would not approve any generic version of the drug that did not also contain abuse-deterrent features. Still, the new requirement had the effect of blocking generic versions of the drug from immediately becoming available. The Generic Pharmaceutical Association, a trade group representing generic drug makers, emphasized what it called the importance of balancing patient access to medicine with efforts to minimize abuse.