Congratulations, Merck (NYSE:MRK). Your acquisition of Schering-Plough (NYSE:SGP) just got a little more valuable.

Merck's fiance announced today that the Food and Drug Administration approved its schizophrenia and bipolar drug, Saphris. The drug has had a schizophrenic set of owners: Organon Biosciences owned the drug and partnered with Pfizer (NYSE:PFE) for a while before Pfizer abandoned the drug. Then Schering bought Organon, and Merck will be Saphris' latest owner when it closes the acquisition of Schering later this year.

Saphris enters a pretty crowded market for antipsychotics, including Bristol-Myers Squibb's (NYSE:BMY) Abilify, Eli Lilly's (NYSE:LLY) Zyprexa, Pfizer's Geodon, and Johnson & Johnson's (NYSE:JNJ) Risperdal. Unfortunately for J&J, the latter recently became available as a generic. To be fair, though, there are quite a few blockbuster antipsychotics, so it's a fairly large market.

For now, though, Saphris isn't going to be a blockbuster. It's only approved to treat acute episodes and until Schering, or more likely Merck, gets it approved for long-term maintenance use, Saphris is likely to be a minor player.

There is long-term hope for Saphris, though. The drug appears to have milder side effects than current antipsychotics. For instance, 14.7% of patients who took Saphris for 52 weeks increased their body weight by 7% or more. By contrast, 18% of patients on Risperdal for just six to eight weeks experienced the same amount of weight gain.

In and of itself, Saphris' approval isn't going to make much of a difference in the value of Schering. But the approval does highlight the reason that Merck purchased Schering: its well-stocked pipeline. If Schering's pipeline continues to deliver, the acquisition should make investors less depressed and more prone to euphoria.

Unlike pharma drug approvals, when biotech companies get a drug approved, big things happen.

Johnson & Johnson is an Income Investor recommendation. To see how dividend-paying stocks can offer both secure income and the opportunity for growth, take a free look at this newsletter with a 30-day trial.

Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. Pfizer is a recommendation of the Inside Value newsletter. The Fool has a disclosure policy.