Prescription weight-loss drug Xenical hit drugstore shelves on Friday with a new name -- Alli (pronounced: "Al-eye") and with a new non-prescription strength. The newly-named drug is to be more effective with less unpleasureable side effects. Still, there's a problem surrounding this drug, regardless of its name. It's thought to cause colon cancer.

The nonprofit group Public Citizen says Alli, made by GlaxoSmithKline, has been shown in mice studies to cause pre-cancerous lesions in the colon. Since there are no long-term studies on humans, this group believes the FDA should not have approved the drug for non-prescription use. It's not clear whether or not the pre-cancerous spots will lead to colon cancer but the mere suggestion that it might is enough, says a Public Citizen spokesperson.

"What we do know is that these lesions occur much more frequently in people who do get colon cancer," he said. "Why do we recommend that everyone get a colonscopy at the age of 50? Because you pick up on these polyps when you do one. And, even though not all of the polyps are pre-cancerous, no (doctor) does a colonscopy without removing every single polyp that is found. And you do this because you know if you don't, it greatly increases the chances of getting cancer."

The FDA says there is not enough evidence to link Alli and colon cancer -- or breast cancer, another Public Citizen concern.