Lidocaine

Lidocaine, sometimes called lignocaine or Xylocaine, belongs to the amino amide class of local anesthetics. Beyond numbing, it is a treatment for ventricular tachycardia and ventricular fibrillation. When injected as a local anesthetic or nerve block, it usually takes effect within a few minutes and can last from thirty minutes up to three hours. It can also be applied directly to skin or mucous membranes to produce numbness. Often, a small amount of adrenaline (epinephrine) is mixed in to extend the numbing effect and reduce bleeding.

If given intravenously, lidocaine may cause confusion, visual changes, numbness, tingling, and vomiting. It can also lead to low blood pressure and an irregular heartbeat. Injecting it into a joint raises concerns about cartilage damage. It is generally considered safe during pregnancy. People with liver problems may need a lower dose. Those allergic to tetracaine or benzocaine can typically use lidocaine safely. As a class Ib antiarrhythmic, it blocks sodium channels, which slows the heart’s contraction rate. When injected near nerves, it prevents those nerves from sending signals to or from the brain.

Lidocaine was discovered in 1946 and became available for sale in 1948. It is on the World Health Organization’s List of Essential Medicines and is available as a generic. In 2023, it was the 277th most prescribed medication in the United States, with over 800,000 prescriptions.

**Medical uses**

**Local numbing agent** As a local anesthetic, lidocaine works quickly and lasts a moderate amount of time. It is used for infiltration, nerve blocks, and surface anesthesia. For spinal and epidural anesthesia, longer-acting drugs like bupivacaine are often preferred, but lidocaine’s fast onset is an advantage. It is one of the most common local anesthetics in dentistry, given as a nerve block or infiltration depending on the procedure and area of the mouth. For surface anesthesia, various formulations are used before endoscopies and intubations. Lidocaine drops are applied to the eyes for short ophthalmic procedures. There is some evidence for topical lidocaine in treating neuropathic pain and pain at skin graft donor sites. It is also used to treat premature ejaculation. A 5% lidocaine hydrogel patch is FDA-approved for nerve pain from shingles and is also used for pain from compressed nerves or after certain surgeries.

**Heart arrhythmia** Lidocaine is a common class Ib antiarrhythmic given intravenously for ventricular arrhythmias—such as those from acute myocardial infarction, digoxin poisoning, cardioversion, or cardiac catheterization—when amiodarone is unavailable or contraindicated. It should be used after defibrillation, CPR, and vasopressors have been started. Routine preventive use after a heart attack is no longer recommended because the overall benefit is unclear.

**Epilepsy** A 2013 review on treating neonatal seizures recommended intravenous lidocaine as a second-line option if phenobarbital does not stop the seizures.

**Other** Intravenous lidocaine infusions are used for chronic pain and acute surgical pain to reduce the need for opiates, though the evidence quality is poor, making it hard to compare with placebo or epidural. Inhaled lidocaine can suppress coughing by acting peripherally, which helps during intubation and recovery from anesthesia. A 2019 review found that intraurethral lidocaine reduces pain in men undergoing cystoscopy. Lidocaine, along with ethanol, ammonia, and acetic acid, may help treat jellyfish stings by numbing the area and preventing further nematocyst discharge. For gastritis, a viscous lidocaine formulation can relieve pain when swallowed. A 2021 study found that 5% lidocaine spray applied to the glans penis 10–20 minutes before sex significantly improves premature ejaculation; another study found that 5% lidocaine-prilocaine cream applied 20 minutes before sex is also effective.

**Adverse effects** Adverse drug reactions are rare when lidocaine is used correctly as a local anesthetic. Most problems come from the administration technique (leading to systemic exposure) or the pharmacological effects of anesthesia; allergic reactions are uncommon. Too much lidocaine in the bloodstream mainly affects the central nervous system and cardiovascular system. CNS effects appear at lower blood levels, while cardiovascular effects occur at higher levels, though cardiovascular collapse can happen even at low concentrations. Specific effects include:

- CNS excitation: nervousness, agitation, anxiety, apprehension, tingling around the mouth, headache, heightened sensitivity, tremor, dizziness, pupil changes, psychosis, euphoria, hallucinations, and seizures. - CNS depression with heavier exposure: drowsiness, lethargy, slurred speech, reduced sensation, confusion, disorientation, loss of consciousness, slowed breathing, and stopped breathing. - Cardiovascular effects: low blood pressure, irregular heart rate.