Reply: Gabapentin: Abuse, Dependence, and Withdrawal.

We would like to thank Prof Bonnet for the interest and comment on this important clinical topic. The reply summarizes very well most of the salient points made in our article—namely, that there exists a potential for misuse of gabapentin, especially among patients with other substanceabuse issues and that withdrawal symptoms may result after abrupt cessation. Prof Bonnet is entirely correct in the assertion that gabapentin has been successfully and safely used many times since its introduction several decades ago. We also appreciate the sharing of Prof Bonnet’s own experience in treating patients with gabapentin. Clearly, the vast majority of patients for whom it is prescribed use it appropriately, most with good clinical results. But as we outlined, serial case reports have documented the frequency with which some patients may inappropriately utilize gabapentin in an attempt to replace or enhance the effects of illicit drug use. Their concomitant use of alcohol or illicit substances along with inappropriate use of gabapentin was documented in many of the case reports cited and was reiterated in our review. And unfortunately, it is often diverted (as can be done with any medication). In their very timely and extremely well-written recent review, Smith et al performed a summary of Englishlanguage literature regarding “misuse, abuse and diversion” of gabapentin. Very similar to our own work, the body of evidence they collected also showed a large overlap in populations that abuse gabapentin and other street drugs and alcohol. Although not all sources reported the specifics on other substances taken by these patients, it is clear that the abuse of illicit and prescription drugs, as well as alcohol, is a strong risk factor for the abuse of gabapentin as well. Whereas we respect Prof Bonnet’s considerable experience in using gabapentin to treat a large number of patients, over a long period of time, for a wide range of conditions, we cautiously remind all readers that simply because patients have not presented for treatment does not mean that the problem of abuse does not exist. Of course, not all abusers enjoy the insight into their own health required for them to present to a clinic for treatment, whereas others present far too late: take, for example, the British study reporting the incidence of inappropriate gabapentin found during postmortem examinations. In addition, Prof Bonnet’s report of 6 of their own cases of gabapentin withdrawal after abrupt cessation adds further to the body of literature concerning this interesting but unfortunate phenomenon. Their suggestion that gabapentin may only potentiate withdrawal symptoms in patients with other psychiatric or drug-abuse history deserves consideration, but as of now, this theory remains unproven. Unfortunately, without a more detailed description of those patients’ symptoms (other than selective serotonin reuptake inhibitor like or benzodiazepine like), it is difficult for readers to decide for themselves whether the withdrawal phenomena more closely resemble a psychiatric or physiological dependence. It is hoped that future reports of such cases will shed further light on this issue. The underlying theme between both our review and the very similar work by Smith et al is clearly the higher than previously appreciated rate of abuse and misuse of gabapentin. This is especially true among people who abuse alcohol, illicit drugs, and/or prescription medications. An increased awareness of this phenomenon should prompt providers to be very deliberate in their prescribing of this otherwise very effective and beneficial medication. Similarly, the recognition of the possibility of withdrawal following abrupt cessation will help providers diagnose and manage this condition as well.