This week is shaping up to be one heck of a roller coaster for drug companies. In addition to VIVUS' (Nasdaq: VVUS) Qnexa -- discussed previously here -- three other drugs could also hear from the Food and Drug Administration on Friday.

A risky second-chance candidate?
Of the three, Avanir Pharmaceuticals' (Nasdaq: AVNR) AVP-923 is the hardest to make a call on. The drug clearly works well in treating pseudobulbar affect, a neurological disease that causes uncontrollable bouts of crying or laughing. But then it worked well when the FDA turned down the drug back in 2006.

The problem was, and still is, potential safety issues. Acanir lowered the dose of one of the components in AVP-923 to decrease the potential for heart issues. The new formulation seems to meet guidelines. But given what's known about the drug, I wouldn't put it past the safety-conscious FDA to hold AVP-923 to a higher standard than what might be acceptable for a drug that didn't have the same background.

Bug out
Antibiotics have had a bit of a bad luck streak, but Forest Labs' (NYSE: FRX) ceftaroline could change that. The drug received a unanimous vote of confidence from an FDA advisory panel to treat pneumonia acquired in the community -- as opposed to the hospital -- as well as bacterial skin infections.

There's always the possibility of manufacturing issues -- the advisory panel doesn't generally look at that -- but from what's known publicly about the drugs, ceftaroline looks like it has the best chance of approval of the three.

Don't get overheated on this one
Biodel
's (Nasdaq: BIOD) Linjeta phase 2 trial looked good, with the new insulin showing better control of blood sugar than Eli Lilly's (NYSE: LLY) Humulin and Humalog.

The phase 3 trial? Not so much. A trial in type 1 diabetics failed to show that Linjeta worked as well as Humulin. The discrepancy from the phase 2 trial was traced back to blood samples from patients in India that were overheated while on their way to be tested. If you remove those patients from the trial, Linjeta seems to be working as well as Humulin.

Will the FDA buy it? My guess is probably not. Think of it from the agency's point of view: Why bother approving the drug with massaged data when a new trial can answer the question of whether the drug works for sure? That's not fair to investors, especially if a new trial comes back positive, but he who has the approval stamp makes the rules.

A pair of bonus decisions
Bristol-Myers Squibb
(NYSE: BMY) could hear from the FDA about two drugs this week as well. But they're both for expanding already-approved drugs -- Onglyza plus metformin and Sprycel -- so they may not help the company's top line all that much.

Combining Onglyza with a generic diabetes drug called metformin will make it more convenient for patients who are taking both drugs, but it's not going to drive many new sales. Onglyza has had a tough time competing with Merck's (NYSE: MRK) diabetes drug Januvia, and it'll continue to do so unless Bristol-Myers can somehow differentiate Onglyza from the entrenched leader. Onglyza plus metformin doesn't do that, since Merck already sells a combination of Januvia plus metformin called Janumet.

Expanding Sprycel into first-line treatment of chronic myeloid leukemia -- it's currently only used after patients fail Novartis' Gleevec -- should increase sales. But Novartis also has a new CML drug, Tasigna, which also beat Gleevec. Until both drugs are approved for the earlier use, we won't know which one will prosper on the market as a first-line treatment.

Trader beware
Keep in mind that October has been one of the busiest months I can remember for FDA decisions. So far, the FDA has managed to stay on task -- even delivering a decision on Bydureon from Amylin Pharmaceuticals, Eli Lilly, and Alkermes early -- but the agency is in no way required to make a decision by the PDUFA dates.

Investors could get a treat a few days early, but don't be surprised if the FDA has a few pre-Halloween tricks up its sleeve.

I've had my say. Which of these drugs do you think will get approved? Sign off in the comments box below.

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Fool contributor Brian Orelli, Ph.D., doesn't own shares of any company mentioned in this article. The Fool has a disclosure policy.