No one wishes to experience pain. But fortunately when those everyday aches and pains arise, we have over-the-counter medications readily available to help us out. (For a recent review on what the evidence has to say about over-the-counter pain medications, check out the Ask Julie column at Vox with Canada’s own Julia Belluz:
But what if you are experiencing pain that isn’t likely to get better with these over-the-counter medications? Patients with #neuropathic pain find themselves in this category. Neuropathic pain — or as it is sometimes called, #neuropathy — is a type of chronic pain that results from damage to the nervous system. Neuropathic pain can be peripheral, resulting from damage to the peripheral nerves (nerves in your arms, legs, hands, and feet for example) or central, resulting from damage to the brain or spinal cord. Common causes of peripheral neuropathy include diabetes and postherpetic neuralgia (nerve pain following shingles). Causes of central neuropathy can include spinal cord injury and multiple sclerosis.
Neuropathic pain is notoriously difficult to treat and may involve both pharmacological and physical therapies. Although painkillers — both over-the-counter and prescription — may be tried, they are not always successful in treating the pain, and in the case of opioids can lead to abuse and addiction. Other classes of medication, not typically used for pain, can be helpful in the treatment of neuropathic pain. These include antidepressant medications and medications normally used to prevent seizures, called anticonvulsant drugs.
Gabapentin, an anticonvulsant originally developed for the treatment of epilepsy, is sometimes used off label to treat neuropathic pain. It is thought to work by inhibiting the transmission of nerve signals in the brain. While gabapentin has been viewed by some health care professionals as a promising option for the treatment of neuropathic pain, others are concerned about the potential for abuse (at high doses it may be associated with sedative and dissociative or psychedelic effects).
Because of the uncertainty of the role of gabapentin in the treatment of neuropathic pain, decision-makers in the Canadian health care system turned to the Rapid Response service at #CADTH — an independent, evidence-based agency that finds, assesses, and summarizes the research on drugs, medical devices, and procedures — to find out what the evidence says.
When CADTH searched for the evidence on gabapentin and neuropathic pain, they found 19 relevant publications — nine systematic reviews, two randomized controlled trials, six non-randomized studies, and two guidelines. Overall, the evidence suggests that gabapentin is effective in the treatment of neuropathic pain. A greater reduction in neuropathic pain was found with gabapentin compared with placebo (no active drug) in adults who have a variety of conditions, including diabetic peripheral neuropathy and postherpetic pain. For short-term treatment of painful diabetic neuropathy and postherpetic neuralgia, gabapentin may be as effective as two classes of antidepressants known as tricyclic antidepressants and serotonin norepinephrine reuptake inhibitors, and another drug for seizures called pregabalin — but these findings are based on indirect evidence (evidence on each drug individually rather than evidence that directly compares the drugs with one another). The evidence for gabapentin for other types of neuropathic pain is limited.
The number of adverse events was higher in patients taking gabapentin compared with patients taking placebo (side effects reported include somnolence, dizziness, peripheral edema, and gait disturbances); but, overall, serious adverse events were few and comparable between the two groups. Gabapentin may be used as a recreational drug, but there is an absence of high-quality evidence on the prevalence and risk of misuse among patients prescribed the drug to manage neuropathic pain.
No Canadian evidence-based clinical practice guidelines were identified, but UK guidelines support the use of gabapentin as one of the first-line treatment options for the management of neuropathic pain. US guidelines recommend gabapentin as an option for diabetic neuropathy.
Knowing the evidence on gabapentin for the treatment of neuropathic pain can help to guide decisions about its use — as well as identify areas where more research is needed. As more evidence on gabapentin and neuropathic pain becomes available, further reviews may be necessary to ensure policy and clinical practice is in keeping with the latest evidence.
If you’d like to see what other drugs, devices, or procedures have been covered by the Rapid Response service at CADTH, visit www.cadth.ca/RapidResponseReports. Here you’ll find all of the freely available reports listed chronologically as they are completed. To learn more about CADTH, visit www.cadth.ca , follow us on Twitter: @CADTH_ACMTS, or talk to our Liaison Officer in your region: https://www.cadth.ca/contact-us/liaison-officers.