In this video, health-care analyst David Williamson looks at Vivus' first-quarter results and breaks it down into key takeaways for investors in both Vivus and its competitor Arena. Watch and find out why shares of the obesity-drug maker went up despite missing sales estimates and what it means now that Arena has received DEA scheduling.

David Williamson has no position in any stocks mentioned. Follow David on Twitter: @MotleyDavid.

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