By Pat Anson, Editor
British researchers say two drugs commonly prescribed as alternatives for opioid pain medication are linked to a rising number of heroin overdose deaths in England and Wales.
Pregabalin and gabapentin belong to a class of nerve medications known as gabapentoids. They were originally developed to treat epileptic seizures, but are increasingly prescribed to treat neuropathy, fibromyalgia and other chronic pain conditions. The drugs are sold by Pfizer under the brand names Lyrica (pregabalin) and Neurontin (gabapentin).
Researchers at the University of Bristol reported in the journal Addiction that opioid overdose deaths in England and Wales involving gabapentoids increased from less than one per year prior to 2009 to 137 deaths in 2015. The increase coincided with a surge in pregabalin and gabapentin prescribing in Wales and England, from one million prescriptions in 2004 to over 10 million in 2015.
Researchers say the increased prescribing has made the drugs easier to obtain and abuse, and addicts have found they enhance the effects of heroin. Experiments on laboratory mice found that pregabalin slows respiratory depression, increasing the risk of an opioid overdose.
"It is important that doctors and people dependent on opioids are aware that the number of overdose deaths involving the combination of opioids with gabapentin or pregabalin has increased substantially and that there is evidence now that their concomitant use - either through co-prescription or diversion of prescriptions - increases the risk of acute overdose deaths,” said Matthew Hickman, a Professor of Public Health and Epidemiology in the University of Bristol's School of Social and Community Medicine.
The idea that Lyrica and Neurontin are being abused may be surprising to many patients and doctors, but the drugs are increasingly being used by addicts. In a small 2016 study of urine samples from patients being treated at pain clinics and addiction treatment centers, over one in five patients were found to be taking gabapentin without a prescription.
“The high rate of misuse of this medication is surprising and it is also a wakeup call for prescribers. Doctors don’t usually screen for gabapentin abuse,” said Poluru Reddy, PhD, medical director of ARIA Diagnostics in Indianapolis. “These findings reveal that there is a growing risk of abuse and a need for more robust testing.”
High Risk of Abuse in Prisons
Gabapentin and pregabalin are also being abused by inmates. Jeffrey Keller, MD, chief medical officer of Centurion, a private correctional company, says both drugs have a high abuse potential.
“Gabapentin is the single biggest problem drug of abuse in many correctional systems,” Keller recently wrote in Corrections.com. “There is little difference (in my opinion) between Lyrica and gabapentin in both use for neuropathic pain or for abuse potential.”
Why would someone be so desperate to abuse them?
“If you are addicted, or even if you just like to get high once in a while, and you can’t obtain your preferred drugs of abuse because you are incarcerated, these are the drugs that can serve as an alternative in a pinch,” Keller wrote.
“It is critically important for medical professionals in corrections to know which seemingly benign drugs have the potential to be abused and diverted. Even if a particular inmate doesn’t care about getting high himself, he can still profit by selling these drugs to others who are. Vulnerable inmates can be (and are) bullied into obtaining these drugs for distribution.”
Gabapentin is approved by the FDA to treat epilepsy and neuropathic pain caused by shingles. It is also prescribed “off-label” for depression, migraine, fibromyalgia and bipolar disorder. About 64 million prescriptions were written for gabapentin in the U.S. in 2016, a 49% increase since 2011. Gabapentin is not scheduled by the DEA as a controlled substance.
Pregabalin is a Schedule V controlled substance, which means the DEA considers it to have a low abuse potential. Pregabalin is approved by the FDA to treat diabetic nerve pain, fibromyalgia, epilepsy, post-herpetic neuralgia caused by shingles and spinal cord injury. It is also prescribed off label to treat a variety of other conditions. Lyrica is Pfizer’s top selling drug, generates over $5 billion in annual sales, and is approved for use in over 130 countries.
The CDC’s opioid prescribing guidelines recommend both pregabalin and gabapentin as alternatives for opioids, without saying a word about their potential for abuse or side effects.
“Selected anticonvulsants such as pregabalin and gabapentin can improve pain in diabetic neuropathy and post-herpetic neuralgia. Pregabalin, gabapentin, and carbamazepine are FDA-approved for treatment of certain neuropathic pain conditions, and pregabalin is FDA approved for fibromyalgia management,” the guidelines state.