Can Botox reduce muscle mass in arms or legs?

Cosmetically muscle mass reduction has been done with Botox in the masseter muscles (chewing muscles) of the face, but the number of units injected for this would be much, much less than that needed to reduce the mass of  muscle in the calf or arm.  The units for the leg or arm may be so high that the treatment could be extremely unsafe.  Neurologists are accustomed to treating muscular dystrohies with large amounts of botox but this is for a functional, not cosmetic, problem.

Hi Gems.  Botox has been used in the way you are suggesting here, but we have never offered this at our practice.  

The first issue is that extremely high doses of Botox would be required to relax and atrophy the muscles.  This would be extremely costly and could be very dangerous.  Careful and ethical physicians would most likely not take on a request like this as it is not a well accepted use for Botox.

Consistent Botox injection into facial muscles can reduce the muscle mass by blocking the function of the muscles injected, causing the muscles to atrophy (or shrink) over time due to non-use. This effect of shrinking the muscles comes at the cost of muscle function. Botox is not intended to reshape the entire body. Not only would it take a huge amount of Botox to combat arm and leg muscles, but the function of your arm and leg muscles is not expendable. The best way to shrink these muscles is to not exercise them specifically. Also, is it really the muscle mass you are worried about, or overall volume? In most people excess arm or leg volume is fat, not muscle. If that is the case exercising and building those muscles will help burn the fat.