Hi Meagan, I am not an expert but I got interested in your question. Here is what I found out:

• Underlying mechanism

The mechanism is a little complex, but in a nutshell, it basically consist on the binding, translocation, rupture and then, once inside the neuron, activation via only the catalytic domain (the light chain of the toxin). When disrupted, the toxin prevent SNAREs-like proteins to bind vesicles (so no ACh is released). So no ACh equals to no neurotransmitions between nerves and muscles. Chapter 2 on the book Botulinum Toxin Treatment What Everyone Should Know, by Bahman Jabbari (2018).

• Recovery

"Over time, the nerve ending starts to sprout and the new endings make contact with different muscle fibers. Finally when the binding is over the synapse resumes its full function." So basically the nerve itself finds a way out to renew the fibers. Chapter 2 on the book Botulinum Toxin Treatment What Everyone Should Know, by Bahman Jabbari (2018).

• Regrowth

So, by logic, there is a natural regrowth on the nerve terminals (it should be a complex mechanism). Check this interesting study: Jiang, H., Xiang, Y., Hu, X., & Cai, H. (2014). Acrylamide inhibits nerve sprouting induced by botulinum toxin type A. Neural regeneration research, 9(16), 1525–1531. doi:10.4103/1673-5374.139479.

• And about the metabolism

Yep, there's something already review it, literally...Lance Simpson, The life history of a botulinum toxin molecule, Toxicon, Volume 68, 2013, Pages 40-59, ISSN 0041-0101, https://doi.org/10.1016/j.toxicon.2013.02.014.

Hope it works for you. Salutes... Omar

The human body is a cellular, dipolar, enclosed aqueous entity. All biochemical and biological functions are directly pH, pressure and temperature dependent, achieved through 1) Dynamic equilibrium of 0∆G, the mechanics the free metabolic energy and entropy. 2) Resonance, the matched impedance. 3) Bioelectromagnetic signaling (Maxwell’s equations). Crisscross-like dendritic distribution network, in human body, is like a sheath of electrons. It, in fact, depicts latent 24/7/365 charge of H+ and H- (hydrogen charges), owing to mother ingredients of ingested biogenic molecule. The charges are pre-laden with selective affinity due to exponentially compatible characteristics of neurotransmitter, acetylcholine. The neurotransmitter acetylcholine serves as pre and post-synaptic signaling medium of evoked homoeopathic medicinal stimuli signaling to the targeted receptor diseased site. The above chain of actions enables the brain chemistry to produce an impulse capable of producing positive energy bonds thus regulating the vasomotor function. The restoration of the blood supply to locally starved areas ensues. The first observable symptom and proof of multi-directional functional characteristics of the homoeopathic medicinal agent lies in “clearing away of the foggy head along with improved internal warmth,” suggesting regulated homoeostasis of the vasomotor induced by homoeopathic medicinal stimuli. Note: Above lines are cited from my book "Quantum Mechanics of Homoeopathy." This is the first ever innovative scientific debate in the field of homoeopathic science. To explore mechanism of action of Botox in human body, you may visit the following link: https://en.wikipedia.org/wiki/Botulinum_toxin

Botox is made from a toxin produced by the bacterium Clostridium botulinum. ... Botox injections work by weakening or paralyzing certain muscles or by blocking certain nerves, with effects lasting roughly three months. However studies show that in rare instances the toxin can spread, paralysing other parts of the body