title: Early pain reduction can predict treatment response: results of integrated efficacy analyses of a once-daily gastroretentive formulation of gabapentin in patients with postherpetic neuralgia.
abstract: OBJECTIVE
  The objectives of this study were to identify and determine the validity of early decision criteria following once-daily gastroretentive gabapentin (G-GR) treatment in patients with postherpetic neuralgia (PHN).
  
  
  METHODS
  In two placebo-controlled studies, 279 patients were randomized to 1,800 mg G-GR and 270 to placebo with the evening meal; patients underwent a 2-week dose titration, followed by 8 weeks of stable dosing, and 1 week of dose tapering. Patients.  Adults with PHN for ≥6 months and an average baseline Numerical Pain Rating Scale (NPRS) score of ≥4 were included in the study.
  
  
  METHODS
  Percent change from baseline to week 10 in NPRS scores and the percentage of responders (defined as ≥30% reduction in NPRS scores from baseline to week 10) were determined.
  
  
  METHODS
  Patients randomized to G-GR were categorized at each week based on their percent pain reduction up to that week, and for each category, the percentage of week 10 responders was computed. For several early-improvement criteria, the percentage of week 10 responders, odds ratios for achieving week 10 treatment response, sensitivity, and specificity were calculated.
  
  
  RESULTS
  There was a significant positive association between early pain reduction and week 10 treatment response. Pain reduction of <10% at week 5 of G-GR treatment was the best early predictor of lack of endpoint response, with only 8% of these patients moving on to become week 10 treatment responders.
  
  
  CONCLUSIONS
  Early response was a reliable predictor of final response. This approach holds promise for aiding clinicians in decision making regarding the need for alternative or supplemental treatment during G-GR therapy for PHN.
authors: Department of Rehabilitation Medicine, University of Washington School of Medicine, Seattle, WA 98104, USA. mjensen@uw.edu
authors: Mark P
authors: MP
authors: Jensen
authors: Ping H
authors: PH
authors: Hsu
authors: Geertrui F
authors: GF
authors: Vanhove
mesh_terms: D000368:Aged; D000588:Amines / Q000008:administration & dosage*; D000700:Analgesics / Q000008:administration & dosage; D003509:Cyclohexanecarboxylic Acids / Q000008:administration & dosage*; D005260:Female; D000077206:Gabapentin; D006801:Humans; D008297:Male; D008875:Middle Aged; D051474:Neuralgia, Postherpetic / Q000175:diagnosis* / Q000188:drug therapy*; D010147:Pain Measurement / Q000379:methods* / Q000592:standards; D011237:Predictive Value of Tests; D013997:Time Factors; D016896:Treatment Outcome; D005680:gamma-Aminobutyric Acid / Q000008:administration & dosage*
chemical_list: D000588:Amines; D000700:Analgesics; D003509:Cyclohexanecarboxylic Acids; D005680:gamma-Aminobutyric Acid; D000077206:Gabapentin