Intended and unintended consequences of the gabapentin off-label marketing lawsuit among patients with bipolar disorder.

Abstract The number of lawsuits accusing pharmaceutical companies of off-label marketing has risen in recent years. The impact of such lawsuits on drug prescribing and spending has not been examined. We evaluated a nationwide sample to determine whether the $430 million gabapentin off-label marketing lawsuit and accompanying media coverage affected gabapentin market share, substitution of other scientifically substantiated and unsubstantiated anticonvulsants, and anticonvulsant spending of Medicare/Medicaid patients diagnosed with bipolar disorder. Using a national 5% sample of Medicare recipients linked to Medicaid claims, we used an interrupted times series design to evaluate the impact of the lawsuit on monthly market share, utilization, and spending from January 1, 2001, to December 31, 2005. The start of the lawsuit was associated with a 28% relative reduction in gabapentin market share (from ∼ 21% to ∼ 15%) and a reduction in the rate of prescribing from 108 prescriptions per 1,000 patients per month before the start of the lawsuit to 90 by the end of follow-up (P