What effect will street drugs have on local anesthesia?

Depends on the drug: It is not recommended to use street drugs prior to any anesthetic. Any procedure involving local anesthetic could potentially require further sedation or general anesthesia and interaction with street drugs could be dangerous. You should not take any prior to a procedure and you should let your anesthesiologist know if you have.

Street drugs: Which, of course are unregulated and may have many chemicals in them that you are not aware of, are harmful to the body and increase the risk of heart attack, stroke, death, and liver dysfunction, to name a few. Elective surgery should not be performed on someone using street drugs because of those risks.

Minimal: Local anesthetics act directly at the site of injection. As such they would not be affected by street drugs.