Botox to reduce arm muscle in a woman?

Thanks so much for your question! Botox works by reducing the activity of certain muscles and therefore improves the appearance of fine lines and wrinkles. Botox does not change the make-up of the muscles and certainly does not degenerate them. I would not recommend pursuing Botox injections in your arm muscle as I have never seen it used in this indication and it would not address your concerns.

Thank you for your question yvtzlm. Botox is a purified protein used to address wrinkles associated with
facial expression. It is used in other areas. However, if used for large muscles a higher dose is required and there is no evidence on the safety of the product in larger muscles. Just like how muscles enlarge (hypertrophy) with exercise they will get smaller without exercise. Please consult with a doctor for specific recommendations. Good luck!

Botox can be used to temporarily reduce the volume of any muscle group on the face or body  I have been using Botox frequently to reduce the bulk of calf muscles and other areas. As long as you find a physician who feels comfortable performing this procedure with good knowledge of anatomy you can definitely entertain this option. 
Good luck from New York City