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Toxicology Rounds: Opioids Not the Only Pain Meds that Lead to Abuse

Gussow, Leon MD

doi: 10.1097/01.EEM.0000526088.16663.8e
Toxicology Rounds

Dr. Gussowis a voluntary attending physician at the John H. Stroger Hospital of Cook County in Chicago, an assistant professor of emergency medicine at Rush Medical College, a consultant to the Illinois Poison Center, and a lecturer in emergency medicine at the University of Illinois Medical Center in Chicago. Read his blog atwww.thepoisonreview.com, follow him on Twitter @poisonreview, and read his past columns athttp://bit.ly/EMN-ToxRounds.

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Figure

Let's call them Drug A and Drug B. They belong to the same pharmaceutical class, and both are frequently prescribed for a wide range of (mostly off-label) indications. They are profitable for the company that makes them, and both commonly and increasingly are misused by people trying to get high.

This misuse is well-documented on drug information websites such as Erowid, where one user described his experience after taking Drug A: “My worries started to fade way.... I get very friendly, very talkative, very active, very uninhibited.... I always get very thoughtful and insanely philosophical.” Another user posted that Drug A produced a sensation “comparable to cannabis with more of a heavy feeling in the body.”

Elsewhere on Erowid, a user reported on Drug B: “My motor function is completely lost as I wander around with a cloud-like feeling of floating. Things seem to be a lot more funny to me than when not taking the drug, like I'm giggling at everything for no reason.”

Of course, plenty of descriptions of bad experiences are online as well. One man posted that Drug A turned him into “a complete zombie—I feel like I've been partially lobotomized.” A woman wrote that Drug B caused her to “shake uncontrollably every day. I became very paranoid and anxious, and the uncontrollable shaking made the paranoia worse.” When she stopped taking Drug B, she experienced headache and anxiety.

Drugs A and B are not new forms of amphetamine or benzodiazepine. They are, in fact, the frequently prescribed medications gabapentin (Neurontin) and pregabalin (Lyrica). They are gabapentinoids, a class of drugs that is the chemical analog of the inhibitory neurotransmitter GAGA (gamma-aminobutyric acid). Although they have been around for decades, gabapentinoids' potential for misuse and abuse has only recently been appreciated. Many clinicians are still not aware that these medications are frequently diverted and sold as recreational drugs with a street value of up to $20 per pill.

A recent article pointed out that the gabapentinoids have FDA approval only for treating partial-complex seizures and postherpetic neuralgia. (New Engl J Med 2017;377[5]:411.) Pregabalin is also approved for fibromyalgia and neuropathic pain associated with diabetes and spinal cord injury. Despite these extremely circumscribed official indications, many practitioners prescribe gabapentin or pregabalin off-label for almost any type of pain and other unproven indications. (See Table 1.) Because of this widespread off-label use, gabapentin was the 10th most frequently prescribed drug in the United States, and pregabalin was eighth in invoice price spending in 2016. For a pharmacologic comparison of gabapentin and pregabalin, see Table 2.

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A Waste of Money

A recent comprehensive systematic review discussed the diversion and recreational use of gabapentin and pregabalin. The authors reviewed medical literature pertaining to the misuse of these, and identified 59 relevant studies. (Drugs 2017;77[4]:403.) They noted that the gabapentinoids mimic the effects of the inhibitory molecule GABA, but they do not act directly on GABA receptors. Rather, they bind to a subunit of the calcium channel, decreasing the release of excitatory neurotransmitters such as norepinephrine and glutamate. They may also indirectly increase the availability of GABA. Gabapentinoids also have dissociative properties similar to those of dextromethorphan.

Table 1

Table 1

Table 2

Table 2

People at increased risk of misusing gabapentin and pregabalin are those with a history of substance abuse disorder, especially if it involves opioids. Gabapentinoids are sometimes misused to increase the effects of buprenorphine or methadone and to self-treat symptoms of withdrawal from opioids, cocaine, and ethanol.

Effects associated with the recreational use of gabapentinoids include euphoria, sedation, relaxation, increased sociability and empathy, and decreased inhibitions. Some users described an irresistible urge to talk to strangers and sing in public after taking gabapentinoids on online drug bulletin boards. They also described visual hallucinations, and reported that their experiences were similar to those taking opioids, benzodiazepines, and psychedelics.

Abusers of gabapentin and pregabalin often take amounts greater than the maximum daily therapeutic doses of 3,600 mg and 600 mg, respectively. The drug is most often ingested, but is also injected, snorted, smoked, rectal-plugged, and parachuted (swallowing crushed drug wrapped in paper).

Many accounts of gabapentin or pregabalin misuse describe dependence and withdrawal following attempts to stop or decrease the dose. One case report describes a 53-year-old woman admitted to a hospital for an upper GI bleed. (Am J Health Syst Pharm 2010;67[11]:910.) All her medications, including gabapentin 700 mg daily, were stopped in the ICU. She became restless, confused, agitated, and anxious on hospital day three. These symptoms did not respond to lorazepam, but resolved after two of her prescribed medications (gabapentin and trazodone) were restarted. The authors referenced two similar cases, and suggested that benzodiazepines may not effectively treat gabapentin withdrawal.

Although gabapentinoids are not generally life-threatening even when taken in significant overdose, all physicians should be knowledgeable about the abuse potential of these agents and the risk of dependence and withdrawal effects. Gabapentin and pregabalin have not been proven to be effective analgesics for many types of pain. These drugs are often a waste of money and an impediment to determining more effective treatment for chronic pain.

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