The only people who legitimately might need vitamin B12 injections would be those with confirmed diagnoses of pernicious anemia, said Dr. George Blackburn, director of the Center for the Study of Nutrition Medicine at Beth Israel Deaconess Medical Center. "And it's virtually impossible" to get pernicious anemia in modern America, where there is ample access to fish, eggs, and dairy products.

For anyone else who uses vitamin B12 shots, the only benefit is in their head, he said. Moreover, since B12 is a water soluble vitamin, extra doses of B12 just pass through the body and out in the urine.

Lidocaine, a painkiller used to treat pain in a localized site, is a different story. Many athletes who have pain in a specific site do get injections of Lidocaine or other painkillers such as Marcaine, which lasts three to four hours, much longer than Lidocaine, said Dr. Zahid H. Bajwa, an assistant professor of anesthesia and neurology at Beth Israel Deaconess.

There has been speculation that Clemens may have had Lidocaine injections into his buttocks. "I don't know why you would inject Lidocaine deep into this muscle if in fact he did," said Dr. Gary Wadler, a spokesman for the American College of Sports Medicine and a member of the World Anti-Doping Agency. In general, painkillers like Lidocaine are used very specifically to block nerves - and therefore - pain in a very specific part of the body, such as certain teeth during dental procedures or around aching joints.