Ten years ago, the thought of being injected with a deadly neurotoxin seemed mighty weird. Now, botulinum exotoxin A has been approved for cosmetic use, and everybody's getting rid of wrinkles. Researchers in this study report on the technique for Botox injections. The toxin comes in a little bottle, but it isn't injected straight; it's diluted, and there's disagreement about how diluted it should be.

What the researchers wanted to know: Does the amount of saline that Botox is mixed with affect the area it treats?

What they did: The researchers recruited 10 adults with "dynamic forehead rhytids"—an extra-nice way to say "big wrinkles." Then each person was injected with two shots of Botox, one on each side of the forehead. Both sides received the same amount of Botox stuck into their forehead muscles, and both shots were diluted with saline solution, but the solution on one side had five times as much saline as the other. The subjects exercised their forehead for an hour after getting the shots. Two weeks later, they came back and a doctor looked at their foreheads to see how big an area was affected.

What they found: In 9 out of 10 subjects, the side that got the larger-volume shot was affected over a larger area even though both shots had the same amount of toxin in them. In the other person, the affected areas were the same size on both sides.

What the study means to you: The researchers say doctors could change the dilution of Botox depending on the area they want to cover—a little bit of Botox in a lot of saline for a larger area or a little bit of Botox in a little bit of saline for a small area.

Caveats: Weaker solutions might not work as well; the researchers didn't look at how long the injections lasted or how well they paralyzed the muscles. (But some studies have suggested that a weaker solution might actually work better.) Also, this work covered the forehead and may not apply to other wrinkles.

Find out more: Read a 2002 warning from the American Academy of Dermatology about Botox parties, where people receive Botox injections at a casual social gathering rather than in a controlled medical setting.

Read the article: Hsu, T.S.J., et al. "Effect of Volume and Concentration on the Diffusion of Botulinum Exotoxin A." Archives of Dermatology. November 2004, Vol. 140, pp. 1351-1354.

Abstract online: http://archderm.ama-assn.org