Juvederm placed in the lips can be painful if no local or topical is used. Some of my patients take it "cold" - no anesthetics. Most take at least a topical.
For the more sensitive patients, I will often place a topical on the skin for 30 minutes, and add a viscous lidocaine solution to be placed along the gum line inside the mouth for about 5-10 minutes prior to performing nerve blocks. This makes the lip completely anesthetic and very easy for the patient.
I am sure you were just very nervous, and that is why you fainted. My patients often comment on how easy the procedure went.



