Pharmaceutical companies' payments to doctors may be influencing them to prescribe more expensive, brand-name versions of the pain drug gabapentin, a team of researchers report in the July 8 issue of JAMA Internal Medicine, and the increasing use of the drug suggests it may be being abused.
"We found that the more physicians receive industry money, the more likely they were to prescribe gabapentin. But more research is needed to understand how much of that gabapentin goes to drug abuse," says lead author Greg Rhee, an assistant professor of medicine and public health at UConn Health.
Gabapentin is a fairly old drug, normally prescribed to control seizures and treat nerve pain. But use of the drug has increased 3-fold in the US between 2002 and 2015, and Rhee and his colleagues wanted to understand why. It is chemically similar to the brain chemical gamma-aminobutyric acid, known as GABA. Gabapentin seems to work similarly to GABA by calming overexcited brain cells, which is why it is sometimes used to treat epilepsy. The way it relieves nerve pain is less well understood. But because it doesn't interact dangerously with other drugs nor cause euphoria when taken at therapeutic doses, it is frequently prescribed for chronic pain. And its use has been increasing: prescriptions of gabapentin and analogs of it rose from 1.2% of US adults in 2002 to 3.9% of US adults in 2015.
Rhee and colleagues from Yale University wondered whether payments from the pharmaceutical industry to doctors might be influencing prescribing. They looked at the Open Payments and Medicare Part D Prescriber databases for 2014-2016. Both databases are made available through the Centers for Medicare and Medicaid Services. Open Payments is a national program that obligates drug manufacturers to disclose payments made to physicians. Medicare Part D Prescriber database shows all the prescriptions made to people in Medicare Part D plans, and is searchable by doctor and by drug.
Gabapentin manufacturers paid physicians $11.5 million between 2014 and 2016, Rhee and his colleagues found. The payments went to about 14% of the doctors who prescribed any kind of gabapentin in those years, mostly pain doctors and general practitioners, most of whom were located in the southern and eastern parts of the country.
The researchers found that doctors who received payments from industry were more likely to prescribe a brand name version of gabapentin such as Lyrica, Gralise or Horizant. These brand name drugs cost several hundred dollars for a one month supply, compared to less than $20 for a one month supply of the generic. Besides cost, the rise in prescriptions is concerning because gabapentin has the potential to be abused. Although it is not reported to be intoxicating when used as directed, searching for gabapentin on drug experience websites such as erowid shows that taking it in larger quantities can cause a long lasting high. Some long-term users who took gabapentin at therapeutic doses for legitimate medical reasons also report it can be addictive. Rhee and his colleagues are concerned that the three-fold increase in prescriptions over the last decade and a half indicate some gabapentin is being diverted for recreational purposes, but caution that more research needs to be done before that can be determined.
This work was funded by the National Institutes of Health grant #T32AG019134.