Ī priori, gabapentinoids represent attractive candidate molecules for psychiatric indications because of their mode of action. In the United States, pregabalin (but not gabapentin) has been a federally controlled drug since market availability because of its potential for dependence and abuse. Moreover, these drugs have potential harms, including a range of serious side-effects, and evidence of misuse and addiction potential, leading to their re-categorisation as controlled drugs in the UK in 2019. Overall, these studies show that there is limited evidence for the efficacy of gabapentinoids in several of the disorders for which they are used. Gabapentinoids may also be of benefit in the treatment of insomnia in some conditions, but again the evidence is unclear. A review of pregabalin for preoperative anxiolysis did not attempt a quantitative synthesis. The efficacy of pregabalin is well established in GAD but is unclear in other anxiety diagnoses such as social anxiety disorder. These studies did not examine pregabalin, did not attempt a quantitative synthesis, and only included published studies.īeyond its licensed use for GAD in the UK, pregabalin has been used in the management of other anxiety disorders and acute anxiety states such as preoperative anxiety. Systematic reviews of gabapentin treatment in psychiatric and/or substance use disorders showed inconclusive evidence for efficacy in BD, but possible efficacy for some anxiety disorders. Gabapentin was not found to be effective over placebo in a comprehensive network meta-analysis of pharmacologic treatments in acute mania. A recent survey using the US-based TriNetX electronic health records network showed that gabapentin had been prescribed at least once in 13.6% of patients with bipolar disorder (BD), 11.5% with anxiety disorders, and 12.7% with insomnia disorder for pregabalin, the figures were 2.9%, 2.6%, 3.0% respectively (PJH, unpublished observations).ĭespite the widespread off-label use of gabapentin in BD, the evidence for its efficacy is unclear.
In the UK, at least half of all gabapentinoid prescriptions are off-label, and one in five are co-prescribed with opioids. An early study of 105 Medicaid patients showed that 95% of prescriptions for gabapentin were for off-label indications, at least 10% of which were for psychiatric disorders. Since their introduction in 1993, these drugs have become two of the most commonly prescribed medications, with a significant proportion likely to have been off-label. Pregabalin has similar indications, as well as for fibromyalgia in the USA and generalised anxiety disorder (GAD) in the UK. Gabapentin is licensed for use in the USA for the treatment of focal seizures and post-herpetic neuralgia and in the UK for focal seizures and peripheral neuropathic pain.
The gabapentinoids comprise gabapentin and pregabalin. This recommendation applies despite the attractive pharmacological and genetic rationale for targeting voltage-gated calcium channels. We conclude that there is moderate evidence of the efficacy of gabapentinoids in anxiety states, but minimal evidence in bipolar disorder and insomnia and they should be used for these disorders only with strong justification. Notably, pregabalin (SMD -0.55, 95% CI -0.92 to -0.18) and gabapentin (SMD -0.92, 95% CI -1.32 to -0.52) were more effective than placebo in reducing preoperative anxiety. Across the anxiety spectrum, a consistent but not universal effect in favour of gabapentinoids compared to placebo was seen (standardised mean difference ranging between -2.25 and -0.25). A quantitative synthesis could not be performed due to heterogeneity in the study population, design and outcome measures. For bipolar disorder, four double-blind RCTs investigating gabapentin, and no double-blind RCTs investigating pregabalin, were identified. Fifty-five double-blind randomised controlled trials (RCTs) and 15 open-label studies were identified. We conducted a systematic review and meta-analysis of the evidence for three of their common psychiatric uses: bipolar disorder, anxiety, and insomnia. Many of these uses are off-label for psychiatric indications, and there is increasing concern about their safety, so it is particularly important to have good evidence to justify this usage. Initially licensed for pain and seizures, they have become widely prescribed drugs. The gabapentinoids, gabapentin, and pregabalin, target the α 2δ subunits of voltage-gated calcium channels.
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