Detailed summary, study No.4, Parke-Davis 945-211

This 8-week randomized, double-blind study compared the efficacy of gabapentin to placebo for the treatment of post-herpetic neuralgia. As in study 945-210, gabapentin (or matching placebo) was sequentially titrated through a range of dosages (900, 1800, 2400 mg/day) until a dosage of 3600 mg/day was reached, or the highest well tolerated dosage below 3600 mg/day. This "force titration" phase was 4-weeks in duration. During the second 4-week period of double-blind treatment, the maximum well tolerated dosage of gabapentin was maintained. As mentioned previously, this forced-titration design - to a single gabapentin dosage, or to the next highest dosage based on tolerability - is insufficient to establish a dose- response relationship for the drug. The primary efficacy measurement was the change from baseline in the average daily pain rating scores (similar to 945-210). The pain score was derived from an 11-point Likert scale in which 0 represented "no pain" and 10 represented the "worst pain possible." Results showed that gabapentin treated patients experienced a statistically significant reduction in the mean pain score from baseline relative to placebo-treated patients (p=0.001). However, as for study 945-210, the study design was insufficient to determine the dose-response relationship of gabapentin since a single final dosage (3600 mg/day) was used in the trial. Thus, this study does not provide substantial evidence of increased efficacy of gabapentin for post-herpetic neuralgia at doses above 1800 mg/day.