What: Shares of BioDelivery Sciences International (NASDAQ:BDSI)a specialty pharmaceutical company with deep interests in the areas of pain management and addiction, climbed by as much as 20.8% today on heavy volume. This sudden rise in the drugmaker's shares was caused by the announcement that the U.S. Food and Drug Administration approved Belbuca, a buccal film for use in patients with chronic pain severe enough to require daily, around-the-clock, long-term opioid treatment and for which alternative treatment options are inadequate. Belbuca was co-developed with Endo Pharmaceuticals, a subsidiary of Endo International (NASDAQ:ENDP)

So what: The chronic pain management market is staggeringly large, with some industry experts suggesting that total sales in this area could reach $60 billion this year alone. Even so, there is a huge need for new medications that can provide relief around the clock and that are easily accessible to patients with debilitating conditions such as advanced heart disease and cancer. BioDelivery and Endo are thus hoping that Belbuca can fill this unmet medical need.

Now what: BioDelivery reportedly earned a $50 million milestone payment upon Belbuca's approval today and stands to earn royalties in the mid-to-high teen range on net sales of the drug. With Belbuca's launch scheduled for the first quarter of 2016, it could thus turn out into an important new revenue source for this tiny drugmaker next year -- especially given that the Street thinks peak sales could top $500 million a year.

Having said that, I'm personally content to wait until the drug's initial sales figures are tallied before buying shares in BioDelivery. After all, the Street frequently misses the mark when it comes to estimating new drug sales, and there's no sure fire way to tell if the market will ultimately adopt a novel drug prior to its commercial launch.