Absolutely. It is common to get injections prior to, or even during anesthesia. That should have no affect on your surgery whatsoever. To save yourself some minor discomfort, I would recommend talking to your plastic surgeon about receiving your botox while you are asleep.
There are 2 methods of injecting the masseter and the medial injections if done may affect the smile. Once this wears off and you want it done again talk with your doctor about not injecting the medial sites
I have performed Botox injections on patients who have a history of breast cancer with their oncologist's approval. Some patients might have a weaker immune system or their blood counts might be affected, but provided that there is not a high probability of bruising nor higher risk of infection...
