Neurologist’s response: You’ll read in the CPS that gabapentin “is indicated as adjunctive therapy for the management of patients with epilepsy who are not satisfactorily controlled by conventional therapy.” Despite this limited indication, millions of gabapentin prescriptions are written in Canada every year to treat other disorders such as pain or psychiatric disease. Of course, physicians can use their own judgement in prescribing approved drugs for unapproved indications but drug companies aren’t allowed to aggressively promote a drug for an indication that Health Canada hasn’t approved.

According to a CBC news story of Feb. 22, 2010, Warner-Lambert settled a U.S. lawsuit in 2004, admitting that “it fraudulently promoted the drug.” This year, a new American lawsuit alleges that Pfizer “misrepresented the drug as a painkiller and understated its risks.”

Clinical pharmacologist’s response: Gabapentin is an anticonvulsant that has become increasingly used for the therapy of neuropathic pain, a type of pain that is both disabling and difficult to treat, as well as being used as a mood stabilizer. Although there’s good evidence that gabapentin is an effective medication for the therapy of neuropathic pain, there have been concerns expressed that the use of gabapentin may be associated with an increased risk of suicidal thoughts. Recent studies analyzing data have supported this concern.

It should be emphasized that these studies demonstrate that the increase in risk for suicidal ideation is a risk associated with therapy with anticonvulsant drugs, i.e. this appears to be a general problem with the class of drugs to which gabapentin belongs. The use of anticonvulsant drugs appears to roughly double the risk of suicidal ideation, from 0.2% to 0.4% of treated patients. This rise in risk starts early (usually by the end of the first week of therapy) and apparently remains elevated for some time. Thus, when treating patients with anticonvulsant drugs, caution their families to monitor for suicidal ideation. There are two things to remember. First, the rate cited is 0.4%, so 99.6% of patients do not have suicidal ideation. Second, the most common adverse event associated with gabapentin therapy is sedation and somnolence, with rates that can be as high as 20%. This, again, is something patients and families should be advised to monitor and anticipate.

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