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The drug: Cymbalta
The companies: Eli Lilly/Shionogi
Estimate worldwide sales for 2012: $5.01 billion

The antidepressant Cymbalta continues to be a big seller for Eli Lilly ($LLY).  In fact, Cymbalta proved to be Lilly's hero after schizophrenia drug Zyprexa, lost patent protection last year. And loathe to give it up, the company is working hard to get what it can from Cymbalta while it can. The patent on the drug lapses at the end of 2013.

For example, in the first quarter this year, Nielsen said Cymbalta topped the list for direct-to-consumer media buys of all drugs in the U.S. when Lilly put out $46.7 million to advertise it. Between that and a price boost, the drug turned in a 7.6% increase in sales for the quarter  bringing in more than $1 billion.

The company also tested the depression treamtent on adolescents through the FDA pediatric-exclusivity program. While the the two pediatric studies the company ran found that the drug did not beat placebo at treating the condition, it got something well worth the effort, a  6-month patent extension to the end of next year. Its patent was slated to expire June 30, 2013.

That extra six months is worth a lot, particularly given so many other drugs in the category have already lost out to generics, drugs like Lexapro, the Forest Laboratories ($FRX) antidepressant. Prozac, Zoloft, Paxil, Celexa, Wellbutrin, Effexor, have all preceded it.

And while it is best known as an antidepressant, two years ago, Eli Lilly won a coveted indication for the drug as a treatment for chronic musculoskeletal pain. That includes osteoarthritis pain and lower back pain--two incredibly common problems, so it gets 6 months more in sales for patients using for those conditions.

For more:
Is the antidepressant glass half-empty or half-full?
Lilly sales reel from Zyprexa loss, but Cymbalta offers aid
Lilly could net $1.5B-plus from Cymbalta extension