Pain
-
The introduction of extended-release opioid analgesics helped initiate an epidemic of prescription opioid abuse in the United States. To make access to the drug by crushing or dissolution more difficult, abuse-deterrent formulations (ADFs) of OxyContin (Purdue Pharma, Stamford, CT) and Opana ER (Endo Pharmaceuticals Inc., Malvern, PA), which use the same foundation technology (Intac, Grunenthal, Aachen, Germany), were introduced in 2010 and 2012, respectively. To examine their relative effectiveness, we used a structured survey of 12,124 individuals entering treatment for opioid use disorder followed by a more focused online survey with a subset of these patients (N = 129) using both structured and open-ended questions. ⋯ However, although the Opana ER ADF was effective in reducing insufflation (80%-37.1%), injection (60.0%-51.4%), and overall nonoral abuse (94.3%-77.1%), it showed no significant decrease over time. Bearing in mind that the Opana ER sample was smaller in size than that for OxyContin, our results nonetheless suggest disparate outcomes resulting from the introduction of the ADFs, which could indicate that an ADF's effectiveness may be drug-specific. Given the public health impact of prescription opioids and the considerable effort being expended to develop ADFs as a partial solution to the problem, our preliminary studies suggest that each ADF must be evaluated on its own merits even if the same proprietary technology is used.
-
The assessment of pain sensitivity in humans has been standardized using quantitative sensory testing, whereas in animals mostly paw withdrawal thresholds to diverse stimuli are measured. This study directly compares tests used in quantitative sensory testing (pinpricks, pressure algometer) with tests used in animal studies (electronic von Frey test: evF), which we applied to the dorsal hind limbs of humans after high frequency stimulation and rats after tibial nerve transection. Both experimental models induce profound mechanical hypersensitivity. ⋯ These data show that rat paw withdrawal threshold to punctate stimuli (0.2 mm diameter) can be used as surrogate parameters for human mechanical pain sensitivity, but probe size and shape should be standardized. Hypersensitivity to blunt pressure-the leading positive sensory sign after peripheral nerve injury in humans-is a novel finding in the tibial nerve transection model. By testing outside the primary zone of nerve damage (rat) or activation (humans), our methods likely involve effects of central sensitization in both species.