"It is possible that the antidepressant effect, rather than an effect on the recovery process itself, might explain the difference [between the two study groups]," said Dr. Larry Goldstein, director of the Duke Stroke Center at the Duke University School of Medicine in Durham, N.C.
Neurologists also say that before recommending that Prozac be part of stroke treatment guidelines, the study should be replicated using more subjects to determine how long patients should take Prozac, whether it's an effect caused by the drug itself or the whole class of medications, the risk of seizures, and the precise mechanism of action.
"Treatments to improve recovery after a stroke are much needed, so anything that promises improvement needs to be considered," said Dr. Joseph Broderick, professor and chair of the Department of Neurology at the University of Cincinnati Neuroscience Institute in Cincinnati.
Viagra is approved for use as a treatment for erectile dysfunction, and is also marketed under the name Revatio to treat pulmonary hypertension, a buildup of pressure in blood vessels leading to the lungs.
Doctors have also used it off-label to increase the blood flow to damaged areas as a way to avoid amputation and the onset of gangrene.
And new promising research may also lead to another use of Viagra: as a treatment for prostate cancer in combination with another cancer drug, doxorubicin.
Researchers from Virginia Commonwealth University discovered that in mice, the combination of Viagra and doxorubicin effectively killed prostate cancer cells and also offered a protection against the well-known cardiac effects of doxorubicin, including cardiomyopathy and heart failure. The study is published in the latest issue of the journal Proceedings of the National Academy of Sciences.
"Doxorubicin has been used for more than 40 years and continues to be one of the most effective drugs against cancer, but the problem is the cardiac effects of this drug," said Rakesh Kukreja, professor of internal medicine at Virginia Commonwealth University in Richmond, Va., and one of the study's authors.
Kukreja said the drug combination was also effective against ovarian cancer and stomach cancer, and the findings show it has great potential as a cancer treatment.
Other experts are not convinced of that treatment potential.
"Everything works against mouse tumors," said Dr. Derek Raghavan, chair and director of the Cleveland Clinic Taussig Cancer Institute. He is not connected with the Viagra study.
"These types of data are what have been seen in the field for years and are doubtful to give a long and/or significant impact to tumor growth," said Robert Gertzenberg, professor of urology at the Johns Hopkins University School of Medicine. He is also not connected with the current research.
Approved for the treatment of enlarged prostate, Avodart, like Propecia, has been tested for prevention of prostate cancer as well.
But the drug from GlaxoSmithKline, chemically known as dutasteride, finds a third use: preventing baldness. Smaller studies have shown some encouraging results.
"It seems to have more benefit [than finasteride] in regrowing hair from pattern hair loss," said Dr. Amy Newburger of Dermatology Consultants of Westchester, N.Y., noting that "it is not yet approved for this indication."