LAUSR

Gabapentin and pregabalin are structurally related compounds which are classified as gammaaminobutyric acid (GABA) analogues or gabapentinoids (Figure 1). Gabapentin, which received American Food and Drug Administration (FDA) approval in 1993, is indicated for the treatment of postherpetic neuralgia, and as adjunctive therapy for refractory partial-onset seizures. It is widely prescribed off-label for diabetic neuropathy and other neuropathic pain conditions. Numerous other off-label and investigational uses for gabapentin have been described, including alcohol dependence,1,2 bipolar disorder,3 posttraumatic stress disorder,4 essential tremor,5 and perioperative anxiety.6,7 Pregabalin, approved for clinical use in the United States in 2004, is indicated for postherpetic neuralgia and partial-onset seizures, and for the treatment of diabetic neuropathy, fibromyalgia, and neuropathic pain associated with spinal cord injury. In a 12-month period frommid-2014 to mid-2015, a total of 39.3 million retail pharmacy prescriptions were written in the United States for gabapentin and 11.0 million for pregabalin.8 Both gabapentin and pregabalin are used off-label for the treatment of various anxiety disorders, especially those that fail to respond to antidepressants and/or benzodiazepines. Pregabalin is currently approved for the treatment of generalized anxiety disorder (GAD) by the European Medicines Agency, but not by the U.S. FDA. This review will focus on the comparative properties of gabapentin and pregabalin, specifically the available evidence on their use in the treatment of primary anxiety disorders — GAD, social anxiety disorder, panic disorder, and obsessivecompulsive disorder. Secondary anxiety symptoms associated with bipolar disorder, substance withdrawal, or posttraumatic stress disorder are not within the scope of the review. Our objective is to update and expand upon previous evaluations of antiepileptic drugs in the treatment of anxiety disorders and other psychiatric conditions.9–16 Comparative Properties of Gabapentinoids