INTRODUCTION: Gabapentin is increasingly being used for the treatment of postoperative pain and a variety of psychiatric diseases, including chronic anxiety disorders. Trials have reported mixed results when gabapentin has been administered for the treatment of preoperative anxiety. We tested the hypothesis that gabapentin 1,200 mg vs placebo would reduce preoperative anxiety in patients who exhibit moderate to high preoperative anxiety.

METHODS: A blinded randomized controlled trial was conducted from September 2009 to June 2011 at the Toronto General Hospital. Following ethics approval and informed consent, 50 female patients with a 0-10 numeric rating scale (NRS) anxiety score of greater than or equal to 5/10 consented to receive either gabapentin 1,200 mg (n = 25) or placebo (n = 25) prior to surgery. Randomization was computer generated, and the Investigational Pharmacy was responsible for the blinding and dispensing of medication. All patients and care providers, including physicians, nurses, and study personnel, were blinded to group allocation. Before administering the study medication, baseline anxiety levels were measured using a NRS, the Spielberger State-Trait Anxiety Inventories, the Pain Catastrophizing Scale, and the Pain Anxiety Symptoms Scale-20. Baseline pain intensity (0-10 NRS) and level of sedation (0-10 NRS and Richmond Agitation-Sedation Scale [RASS]) were also measured. Two hours after the administration of gabapentin or placebo (prior to surgery), patients again rated their anxiety, pain, and sedation levels using the same measurement tools as at baseline. The main outcome was a reduction in preoperative anxiety.

RESULTS: Forty-four patients (22 treated with gabapentin 1,200 mg and 22 treated with placebo) were included in the analysis of the primary outcome. Analysis of covariance in which pre-drug NRS anxiety scores were used as the covariate showed that post-drug preoperative NRS anxiety (Effect size, 1.44; confidence interval [CI] 0.19 to 2.70) and pain catastrophizing (Effect size, 0.43; CI 0.12 to 0.74) scores were significantly lower in the gabapentin group than in the placebo control group, respectively. Post-drug sedation (Effect size, -3.02; CI -4.28 to -1.77) and RASS (Effect size, 0.41; CI 0.12 to 0.71) scores were significantly higher in the gabapentin group than in the placebo group, respectively.

CONCLUSIONS: Administration of gabapentin 1,200 mg prior to surgery reduces preoperative NRS anxiety scores and pain catastrophizing scores and increases sedation prior to entering the operating room. These results suggest that gabapentin 1,200 mg may be a treatment option for patients who exhibit high levels of preoperative anxiety and pain catastrophizing; however, the sedative properties of the medication and the possibility of delayed postoperative discharge in the elective ambulatory population need to be considered.

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