How long is lidocaine good for after it has been drawn up into a syringe and has remained capped?

About 2 weeks. As a Mohs surgeon dermatologist, my days involve use of lidocaine local anesthesia from start to finish. So my assistants draw up large numbers of 3 cc syringes of buffered lidocaine with epi at a time from multi-use vials. They typically get used up within a week, but sometimes for various reasons it can take a couple weeks to use them all. I believe I note some decrease in efficacy at about 2 weeks. I have not noted any increase in infection or other problem with using them that long after draw up.

I wouldnt use it after 12-24 hours, but it may also depend on your facility policy if this is for a patient. If you are at home and this is for yourself or a family member, I would say dont use it after 24 hours, 12 if it is non preservative lidocaine. Even if there are preservatives, one has to consider that you are drawing it up into a new container (the syringe) and even with asceptic technique, you still risk contamination any time you are drawing something up so the longer it is in a syringe, the more bacteria can grow. It can also depend on what you are using it for. Are you injecting as a local or what?