Tox Tuesday: Nerve pain and gabapentinoids

Due to the ongoing opioid crisis, some health care providers are being advised to exercise caution when prescribing opioid painkillers to patients, because of the risk of dependency or abuse. Now, some say this situation could end up reflected with another medication: gabapentinoids, a category of drugs that includes gabapentin and pregabalin.

Gabapentinoids are analgesics traditionally used to treat neuropathic pain. Prescriptions are increasing in number; in fact, their use has increased from 1.2% of the population in 2002 to 3.9% in 2015, according to the U.S. Centers for Disease Control and Prevention. As of 2013, over a five-year period in the United Kingdom, pregabalin prescriptions had increased by 350% and gabapentin prescriptions had increased by 150%. Some propose that this increase is a response to the opioid public health crisis, and the resulting search for alternative painkillers to prescribe.

Neuropathic pain is also referred to as nerve pain, and it results from nerve damage or problems with the nervous system. This kind of pain is described by the Stanford Pain Management Center as brain “signals in the pain pathway activated by processes that should not be painful.” It stems from the somatosensory system, which connects to the part of the brain that receives all sensory input from the body. When something goes wrong in this system, a person might feel sensations that don’t make sense with what’s really happening to the body, hence, nerve pain.

Nerve pain feels like a “pins-and-needles” or burning pain and can also come in the form of numbness and tingling. Nerve pain can be caused by many conditions, like multiple sclerosis and diabetes, as well as by chemotherapy, amputation, spine injuries, strokes, brain injuries and shingles, among other causes. It affects about 10% of the population.

As prescription drugs

Gabapentinoids were originally created to treat epilepsy, and it was only after their development that their uses in treating neuropathic pain were realized.

Gabapentin is recommended for the treatment of diabetic neuropathy, postherpetic neuralgia and central pain. Research has suggested that gabapentin works more effectively when combined with certain other drugs, including the opioid oxycodone. It’s not a scheduled drug in the U.S., but in response to reports of gabapentinoid abuse, some states may be considering making it one — Kentucky already has. There is discussion in the United Kingdom of controlling the drug under the Misuse of Drugs Act.

Another gabapentinoid, pregabalin, is typically used to treat epilepsy, fibromyalgia, generalized anxiety disorder and the same types of neuropathic pain that gabapentin treats. It’s a Schedule V controlled substance in the U.S., meaning it’s been determined as having a low potential abuse that could lead to dependency.

Both gabapentinoids are associated with a few off-label uses. Gabapentin has been prescribed for the treatment of anxiety disorders, bipolar disorder and insomnia, while pregabalin has been prescribed for restless leg syndrome, migraines, anxiety and alcohol withdrawal.

As drugs of abuse

Both drugs have been associated with abuse. During clinical trials, about 4% of pregabalin users reported feeling euphoria, which is why it was classified as a Schedule V drug.

Over time, researchers have begun to question whether the increased number of gabapentinoid prescriptions was contributing to any developing problem of overuse. According to Practical Pain Management, a review of 59 studies shows that gabapentin abuse is more likely when a patient has previous problems with opioid use, more so than previous abuse of other drugs. One study published in December 2017 concluded that prescribers should be careful when working with patients who have a history of opioid addiction, and to look carefully for signs of abuse, noting that reports of abuse were being increasingly documented.

When ingested at levels above the typical therapeutic dosage, gabapentinoids can cause euphoria, dissociation, sociability, a lack of inhibitions, numbness and hallucination. People who abruptly stop taking them can suffer withdrawal symptoms. They’re often taken along side other substances, like alcohol, cannabinoids, opioids, amphetamines and LSD, in order to augment their effects. In other instances, they’re taken to cope with withdrawal from other substances.

Right now, it’s considered fairly easy for recreational use to happen. Painweek outlines a few factors: there are multiple off-label uses, its use is widespread, it’s relatively cheap on the street, getting a prescription is easy, and both drugs are either not controlled or considered to have low potential for abuse. When taken recreationally, the drugs can be taken orally, intravenously or snorted.

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