I have been smoking crack cocaine since 9:30am today and at 3:30pm i have a dental appointment where i will be put under local anesthesia. my risks?

Tell your dentist: because they might want to avoid local anesthetic with epinepherine, as the combination could cause a dangerous rise in heart rate. The bigger issue at hand is the fact that you're smoking crack in the first place. Please seek treatment for your addiction issues. Crack is very dangerous, and if you keep doing it, your health issues will be much worse than local anesthetic.

Not a good idea: I will not recommend to get any treatment for now, anesthesia may not work in this case and you dentist may not be prepared to handle an emergency. In my office I will reschedule you until I get a bill of health from your physician. Get treatment for your addiction because you are putting yourself at risk. Good luck.