Anyone who's kept an eye on the drugmakers this year won't be surprised by this statistic: The Food and Drug Administration approved fewer drugs this year than it has since 2007. According to the Wall Street Journal, which took the time to add them all up, the FDA only approved 21 drugs this year, compared with 25 in 2009 and 24 in 2008.

Dwelling on the past isn't usually all that useful for investors; the markets are forward-looking after all. But a little review of recent drug approvals and rejections is useful to see what the future holds for drugmakers in 2011 and beyond.

Drugs do get approved
It's easy to get wrapped up in the FDA's seemingly schizophrenic rejections, but the simple fact of the matter is the agency does approve drugs.

The easiest way to get a drug approved is to treat an unmet need and pass clinical trials that prove the drug works. Witness Dendreon (Nasdaq: DNDN), which treats metastatic prostate cancer where there aren't many other options. The drug, Provenge, passed its phase 3 trial, and sure enough, the drug was approved.

If a drug fails to meet both criteria, the chances for regulatory success fall substantially.

InterMune's (Nasdaq: ITMN) idiopathic pulmonary fibrosis (IPF) drug, Esbriet, certainly serves an unmet need; there aren't any drugs currently approved to treat IPF in the U.S. But when only half of the phase 3 trials came back positive, a rejection wasn't all that surprising.

On the flip side, obesity drugs from VIVUS (Nasdaq: VVUS) and Arena Pharmaceuticals (Nasdaq: ARNA) met their clinical trial requirements -- VIVUS' Qnexa by a larger margin than Arena's lorcaserin, but they both passed. Nevertheless, the FDA still rejected both drugs because of worries over safety concerns. As much as it disappoints investors and quite a few patients, the FDA doesn't seem to see obesity as being that big of a medical need, especially when diet and exercise can shed the pounds.

Expect the unexpected
That's pretty much the mantra coming out of the FDA lately, which makes it more difficult for investors to handicap the likelihood of an FDA approval.

The biggest surprise of the year was the announcement that Amylin Pharmaceuticals and Eli Lilly would have to prove that their diabetes drug, Bydureon, didn't cause heart problems before the FDA would approve it. The FDA already had already turned the drug down once for relatively minor issues, so it was surprising that the agency would come back with such a large request.

Should have been on this year's list
The number of approved drugs could have had two more additions had it not been for the FDA bumping those decisions into next year.

Human Genome Sciences (Nasdaq: HGSI) and GlaxoSmithKline's lupus treatment Benlysta was due for an FDA decision this month, but the agency delayed its decision by three months. Given the tight timeframe between its advisory panel meeting and decision date, the delay wasn't all that surprising. A short delay isn't that big of a deal; there's a huge unmet need -- there hasn't been a new treatment for lupus in more than 50 years -- so it seems likely that Benlysta will be on next year's list.

This week, MannKind (Nasdaq: MNKD) said the FDA would need about four more weeks to finish its review of its inhaled insulin, Afrezza. Investors figured the delay was good news, but I'm not nearly as convinced. Figuring out how the FDA will side on this one is fairly difficult.

Upcoming in 2011
I have no idea whether we'll see more drug approval in 2011 than we saw this year. Keep in mind that the overall level isn't determined by just the FDA; the number of applications will have some bearing, which is predicated on the number of positive clinical trials.

There are a few drugmakers that we know will be getting decisions in 2011.

Orexigen Therapeutics is due to round out the trio of obesity drugs with a decision on Contrave due at the end of January. Contrave is the only one of the three to get a positive recommendation from its FDA advisory panel, so it has a better chance at an FDA approval than the "somewhere between unlikely and nonexistent" I gave lorcaserin and Qnexa. But an approval is far from guaranteed. The FDA rejected Esbriet after a positive panel, for instance.

At the other extreme, Vertex Pharmaceuticals' (Nasdaq: VRTX) hepatitis C treatment, telaprevir, seems like a shoo-in. Given the extensive data and unmet need -- current treatments only cure about half of patients -- an approval seems all but certain.

Keeping in mind that you still have to expect the unexpected, of course.

Keep up with the drugs facing FDA decisions using The Fool's My Watchlist feature or subscribe to Brian Orelli's RSS feed here.

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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.