Lidocaine, also known as lignocaine, is a medication used to numb tissue in a specific area (local anesthetic). It is also used to treat ventricular tachycardia and to perform nerve blocks. Lidocaine mixed with a small amount of adrenaline (epinephrine) is available to allow larger doses for numbing, to decrease bleeding, and to make the numbing effect last longer. When used as an injectable, it typically begins working within four minutes and lasts for half an hour to three hours. Lidocaine mixtures may also be applied directly to the skin or mucous membranes to numb the area.Common side effects with intravenous use include sleepiness, muscle twitching, confusion, changes in vision, numbness, tingling, and vomiting. It can cause low blood pressure and an irregular heart rate. There are concerns that injecting it into a joint can cause problems with the cartilage. It appears to be generally safe for use in pregnancy. A lower dose may be required in those with liver problems. It is generally safe to use in those allergic to tetracaine or benzocaine. Lidocaine is an antiarrhythmic medication of the class Ib type. This means it works by blocking sodium channels and thus decreasing the rate of contractions of the heart. When it is used locally as a numbing agent, local neurons cannot signal the brain.Lidocaine was discovered in 1946 and went on sale in 1948. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. It is available as a generic medication and is not very expensive. The wholesale cost in the developing world in 2014 was US$0.45 to $1.05 wholesale per 20 ml vial of medication. It is sold under a number of brand names including Xylocaine.