It seems the FDA is taking its newly increased safety mandate pretty seriously. The agency has started repeating its warnings just to make sure everyone knows it's on the job.

Yesterday, the agency posted a safety alert warning that osteoporosis drugs in the bisphosphonates drug class can cause extreme pain for some patients. The class includes Actonel from Procter & Gamble (NYSE: PG) and Sanofi-Aventis (NYSE: SNY), Merck's (NYSE: MRK) Fosamax, Boniva from Roche and GlaxoSmithKline (NYSE: GSK), and Novartis' (NYSE: NVS) franchise including Aredia, Reclast, and Zometa.

The drugs' labels already warn that the drugs can cause severe pain in a small number of patients, but the FDA must have received enough complaints to figure it needed to give doctors a reminder.

It sounds to me like the agency is concerned with making sure doctors recognize that a patient's new pain might be caused by the prescribed drugs; I don't think the FDA is discouraging doctors from actually prescribing the drugs. The FDA did say that it was reviewing reports of pain, so additional warning labels could be in the works when the agency concludes its investigation in six months.

In the meantime, the reminder could cause some doctors to think twice about prescribing the bisphosphonates. Those doctors might prescribe other osteoporosis drugs, such as Eli Lilly's (NYSE: LLY) Evista or Forteo. Both those drugs have side-effect issues of their own, however, so my guess is that these warnings will have a minor effect, if any, on sales of bisphosphonate drugs.

As the FDA tries to show Congress that it's more safety-conscious, investors should expect to sort through more FDA warnings to decide how much effect they'll have on the affected companies.

More Foolishness on FDA warnings:

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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.