Can Botox fix a big orbicularis oris muscle?

It would be very difficult to make such a diagnosis and give you a meaningful advice based only on this photo. In person, dynamic evaluation (smiling, speaking, whistling) would help to understand your problem and discuss possible options to improve it. Hope this helps b

Botox, or botulinum toxin, is a neuromodulator that can temporarily paralyze muscles. It is commonly used in cosmetic procedures to smooth wrinkles and fine lines. When it comes to the orbicularis oris muscle, which is the muscle around the mouth, Botox can be used to reduce its activity. This can result in a decrease in the appearance of lines and wrinkles around the mouth.
However, Botox does not necessarily "fix" a big orbicularis oris muscle. If the muscle is enlarged due to hypertrophy (increased muscle mass), Botox may not significantly reduce its size. It can, however, decrease the muscle's activity, which may in turn reduce muscle mass over time.
It's important to note that Botox should only be administered by a qualified healthcare professional, and potential side effects and complications should be discussed prior to treatment. It's also important to have realistic expectations about the results of Botox treatment.

I encourage you to visit with a board certified plastic surgeon near you to discuss your concerns. Botox around the mouth can lead to unwanted side effects if done incorrectly and may not address your concern. An evaluation is needed to determine the underlying cause of the look that concerns you in order to determine the appropriate treatment.