title: A retrospective study to identify risk factors for somnolence and dizziness in patients treated with pregabalin.
abstract: BACKGROUND
  Pregabalin is a therapeutic drug for neuropathic pain that is associated with somnolence and dizziness. These adverse events are often experienced shortly after initiating pregabalin, and may lead to treatment discontinuation. The purpose of this study was to explore factors that influence the incidence of somnolence and dizziness induced by pregabalin, and to identify patients at higher risk of adverse events.
  
  
  METHODS
  A retrospective analysis was conducted of patient characteristics (age, gender, renal function, initial daily dose of pregabalin, co-administration of strong opioids and hypnotics) and the incidence of somnolence and dizziness during the first week of pregabalin treatment. An electronic chart was used to collect data from 204 inpatients prescribed pregabalin at Nagoya University Hospital from June 2011 to November 2012.
  
  
  RESULTS
  Among 36 patients who regularly received strong opioids, 18 (50.0 %) reported somnolence or dizziness during the first week of pregabalin treatment. The remaining 168 patients did not regularly receive strong opioids, and 25 (14.9 %) had an adverse event. In multivariate analysis, age (≧65 years, adjusted odds ratio: 2.507, 95 % CI: 1.164-5.397, p = 0.019) and regular co-administration of strong opioids (adjusted odds ratio: 5.507, 95 % CI: 2.460-12.328, p < 0.001) correlated with somnolence or dizziness.
  
  
  CONCLUSIONS
  These data suggest that age (≧65 years) and co-administration of strong opioids are risk factors for somnolence or dizziness during pregabalin treatment for neuropathic pain. More careful dose titration is recommended for elderly patients and those receiving concomitant strong opioids.
authors.affiliation: Department of Neuropsychopharmacology and Hospital Pharmacy, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466-8560 Japan ; Division of Clinical Sciences and Neuropsychopharmacology, Meijo University Faculty of Pharmacy, Nagoya, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kato
authors.affiliation: Department of Neuropsychopharmacology and Hospital Pharmacy, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466-8560 Japan ; Division of Clinical Sciences and Neuropsychopharmacology, Meijo University Faculty of Pharmacy, Nagoya, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyazaki
authors.affiliation: Division of Clinical Sciences and Neuropsychopharmacology, Meijo University Faculty of Pharmacy, Nagoya, Japan.
authors.forename: Mio
authors.initials: M
authors.lastname: Takeuchi
authors.affiliation: Department of Clinical Oncology and Chemotherapy, Nagoya University Hospital, Nagoya, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tsukuura
authors.affiliation: Department of Clinical Oncology and Chemotherapy, Nagoya University Hospital, Nagoya, Japan.
authors.forename: Mihoko
authors.initials: M
authors.lastname: Sugishita
authors.affiliation: Department of Neuropsychopharmacology and Hospital Pharmacy, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466-8560 Japan ; Division of Clinical Sciences and Neuropsychopharmacology, Meijo University Faculty of Pharmacy, Nagoya, Japan.
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Noda
authors.affiliation: Department of Neuropsychopharmacology and Hospital Pharmacy, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, Aichi 466-8560 Japan.
authors.forename: Kiyofumi
authors.initials: K
authors.lastname: Yamada
keywords: Cancer pain; Dizziness; Neuropathic pain; Opioid; Pregabalin; Risk factor; Somnolence
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