Lidocaine HCL is a medication used to numb tissue in a specific area. It is also used to treat ventricular tachycardia and to perform nerve blocks. Lidocaine mixed with a small amount of adrenaline is available to allow larger doses for numbing, to decrease bleeding, and to make the numbing effect last longer. When used as an injectable, lidocaine typically begins working within four minutes and lasts for half an hour to three hours.