title: Temporal analysis of pain responders and common adverse events: when do these first appear following treatment with pregabalin.
abstract: BACKGROUND
  Pregabalin is an α2δ ligand indicated in the USA for treatment of a number of chronic pain conditions, including diabetic peripheral neuropathy, postherpetic neuralgia, pain associated with spinal cord injury, and fibromyalgia. A greater understanding of when patients first respond to treatment with pregabalin and when adverse events emerge, or worsen, could aid design of new proof-of-concept studies and help guide treatment of patients.
  
  
  METHODS
  This was an analysis of five randomized, placebo-controlled, double-blind trials (between 8 and 16 weeks in duration) of flexible-dose pregabalin (150-600 mg/day). Individual patient data were pooled into three groups by disease condition: diabetic peripheral neuropathy or postherpetic neuralgia (n=514), spinal cord injury (n=356), and fibromyalgia (n=498). Responders were classified as having a ≥30% and/or ≥50% reduction in mean pain score from baseline; once a patient responded, they were not scored subsequently (and were excluded from the responder analysis). The emergence of adverse events at each week was also recorded.
  
  
  RESULTS
  The majority of the 30% and 50% responders emerged within the first 3-4 weeks with pregabalin, but were more uniformly distributed across the 6 weeks of the analysis with placebo. The majority of common adverse events also emerged within the first 3-4 weeks of pregabalin treatment.
  
  
  CONCLUSIONS
  These data suggest that the majority of pain responders and common adverse events emerge within 3-4 weeks of treatment with pregabalin. These data could advise new proof-of-concept studies and guide clinical management.
authors.affiliation: Pfizer, New York, NY, USA.
authors.forename: Bruce
authors.initials: B
authors.lastname: Parsons
authors.affiliation: Pfizer, New York, NY, USA.
authors.forename: Birol
authors.initials: B
authors.lastname: Emir
authors.affiliation: Pfizer, New York, NY, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Clair
keywords: clinical trial design; fibromyalgia; neuropathic pain