When the FDA
approved the powerful painkiller Zohydro last week, it did so without requiring the drug to have any built-in biochemical mechanisms aimed at curbing abuse.
That
"omission" makes Zohydro very different from opioids currently on the
market, including OxyContin and Opana, both of which have
abuse-deterrent formulations.
Additionally, the FDA has been
taking steps over the past year to make sure all opioid drugs brought to
the market in the future would incorporate such technologies.
This push follows a major criminal case in which executives of Purdue Pharma, maker of the powerful opioid OxyContin,
pleaded guilty to misleading the public about the drug's risk of abuse.
The
company said the drug's extended-release formula would make it harder
to abuse – the same argument initially put forward with the initial
extended release formulation of OxyContin, but crushing OxyContin pills
made them a "drug du jour" for many abusers and forced the company to
add anti-abuse mechanisms.
So why not require extended-release Zohydro to have updated abuse-deterrent properties?
The Road to Abuse-Deterrent Technology
Pleasure-seekers
have found many ways to get extended-release opioid drugs to release
their full punch all at once, instead of being doled out slowly over
many hours. These pills can be crushed, chewed, or mixed with alcohol or
other liquids to extract the active ingredient.
In response,
companies have come up with a number of ways to deter that kind of abuse,
such as making the tablet turn chunky instead of powdery when crushed,
or turning it thick and sudsy when mixed with a liquid and drawn into a
syringe.
Some have even combined their opioids with anti-opioid
agents, such as naltrexone, which block opioid receptors in the brain to
send abusers into withdrawal rather than getting them high.
Last January, the
FDA released a draft guidance
that would require all new opioid drugmakers to incorporate these
properties into their products. But that document has yet to be
finalized.
Bob Twillman, PhD,
director of policy and advocacy for the American Academy of Pain
Management, said even if that guidance was in place, it's likely Zohydro
would have been grandfathered because it was "well into the development
process before abuse-deterrent technology became available."
Indeed,
the drug was first developed in 2002 by Elan (which has now merged with
Alkermes), and Zogenix acquired the U.S. rights in November 2007. The
company
presented Zohydro to the FDA advisory committee just one month before the agency issued its initial draft of the abuse-deterrent guidance.
The issue of abuse-deterrence was a point of contention last spring, when OxyContin maker Purdue Pharma used it as leverage to
banish generic versions of its drug.
In
2010, four years after it was fined, Purdue upgraded its OxyContin
recipe to include abuse-deterrent mechanisms, and it requested that FDA
block generic versions lacking those properties – which the FDA
ultimately agreed to do, effectively giving Purdue extended patent
protection.
But the agency
declined to do the same for Opana,
another extended-release opioid. Drugmaker Endo Pharmaceuticals created
an abuse-deterrent version of the original drug in March 2012.
The
FDA said that unlike old OxyContin, the first incarnation of Opana
wasn't pulled from the market for safety reasons, so generic
formulations would be allowed.
"While FDA strongly supports a
transition to abuse-deterrent opioids, we do not believe it is
appropriate or feasible at this time to require all products in the
class to be abuse-deterrent," Morgan Liscinsky, a spokesperson for the
FDA, said in an email to the
Journal-Sentinel/MedPage Today.
"Rather, FDA will continue to take a product-by-product approach to
regulatory decisions concerning the abuse-deterrent properties (or lack
thereof) of opioid products."
Liscinsky noted, however, that they will be subject to the
class-wide label change put forth by the agency in September, limiting the drugs to patients with severe, refractory pain – not moderate pain.
Patent Protection at Play?
In a statement to
Journal Sentinel/MedPage Today,
drugmaker Zogenix, of San Diego, said the company intends to develop an
abuse-deterrent formulation of the drug and is "committed to advancing
the program as rapidly as possible."
But during the FDA advisory
committee hearing last December, a company spokesperson said an
abuse-deterrent formulation of the drug is only in pre-clinical
development and would be "several years away from the market."
Regardless
of when the updated version comes to the clinic, the strategy of
releasing one product first, followed by an upgrade, undoubtedly extends
patent-protection on the drug, granting it additional years of
exclusivity.
Twillman said his group is concerned about the lack
of abuse-deterrent properties with Zohydro because it can put patients
at "unnecessary risk if they chose to alter their medication."
"While
we do not believe that every person using long-acting opioids needs to
use tamper-deterrent products, we would prefer to see that all new
opioid pain relievers incorporate these features," Twillman said.
David Juurlink, MD, PhD,
director of pharmacology and toxicology at the University of Toronto,
said even parties who typically disagree about the role of opioids in
chronic pain "agree that abuse-deterrent products make sense."
"The
FDA agrees too. Yet in Zohydro, they have granted approval to pure,
high-dose hydrocodone in a formulation that is not abuse-deterrent,"
Juurlink said. "If the FDA was really interested in protecting the
public, they would have said, 'No thanks. There's no therapeutic void
here, and we have too many people dying of opioids in this country to
justify approving Zohydro.'"
Read More : http://www.medpagetoday.com/PainManagement/PainManagement/42511