What is/are Lidocaine topical?
Lidocaine (INN) /ˈlaɪdɵkeɪn/, xylocaine, or lignocaine (former BAN) /ˈlɪɡnɵkeɪn/ is a common local anesthetic and antiarrhythmic drug. Lidocaine is used topically to relieve itching, burning and pain from skin inflammations, injected as a dental anesthetic or as a local anesthetic for minor surgery.
The efficacy profile of lidocaine as a local anesthetic is characterized by a rapid onset of action and intermediate duration of efficacy. Therefore, lidocaine is suitable for infiltration, block and surface anesthesia. Longer-acting substances such as bupivacaine are sometimes given preference for subdural and epidural anesthesias; lidocaine, on the other hand, has the advantage of a rapid onset of action. Epinephrine (aka adrenaline) vasoconstricts arteries reducing bleeding and also delays the resorption of lidocaine, almost doubling the duration of anaesthesia. For surface anesthesia several formulations are available that can be used e.g. for endoscopies, before intubations etc. Buffering the pH of lidocaine makes local freezing less painful.
Topical lidocaine has been shown in some patients to relieve the pain of postherpetic neuralgia (a complication of shingles), though there is not enough study evidence to recommend it as a first-line treatment. It also has uses as a temporary fix for tinnitus. Although not completely curing the disorder, it has been shown to reduce the effects by around two thirds.
Lidocaine is also the most important class 1B antiarrhythmic drug: it is used intravenously for the treatment of ventricular arrhythmias (for acute myocardial infarction, digoxin poisoning, cardioversion or cardiac catheterization).
However, amiodarone has been replacing lidocaine as the first-line pharmacologic management of ventricular tachycardia. A routine prophylactic administration is no longer recommended for acute cardiac infarction; the overall benefit of this measure is not convincing.
Lidocaine has also been efficient in refractory cases of status epilepticus. Inhaled lidocaine can be used as an antitussive (cough suppressor) acting peripherally below the larynx.
Lidocaine has also proved effective in treating jellyfish stings, both numbing the affected area and preventing further nematocyst discharge.
Contraindications for the use of lidocaine include:
- Heart block, second or third degree (without pacemaker)
- Severe sinoatrial block (without pacemaker)
- Serious adverse drug reaction to lidocaine or amide local anaesthetics
- Concurrent treatment with quinidine, flecainide, disopyramide, procainamide (Class I antiarrhythmic agents)
- Prior use of Amiodarone hydrochloride
- Hypotension not due to Arrhythmia
- Accelerated idioventricular rhythm
- Porphyria, especially Acute Intermittent Porphyria (AIP); lidocaine has been classified as porphyrogenic although clinical evidence suggests that it is not.
Adverse drug reactions (ADRs) are rare when lidocaine is used as a local anesthetic and is administered correctly. Most ADRs associated with lidocaine for anesthesia relate to administration technique (resulting in systemic exposure) or pharmacological effects of anesthesia, and allergic reactions only rarely occur.
Systemic exposure to excessive quantities of lidocaine mainly result in central nervous system (CNS) and cardiovascular effects – CNS effects usually occur at lower blood plasma concentrations and additional cardiovascular effects present at higher concentrations, though cardiovascular collapse may also occur with low concentrations. CNS effects may include CNS excitation (nervousness, tingling around the mouth (also known as circumoral paraesthesia), tinnitus, tremor, dizziness, blurred vision, seizures) followed by depression, and with increasingly heavier exposure: drowsiness, loss of consciousness, respiratory depression and apnoea. Cardiovascular effects include hypotension, bradycardia, arrhythmias, and/or cardiac arrest – some of which may be due to hypoxemia secondary to respiratory depression.
ADRs associated with the use of intravenous lidocaine are similar to toxic effects from systemic exposure above. These are dose-related and more frequent at high infusion rates (≥3 mg/minute). Common ADRs include: headache, dizziness, drowsiness, confusion, visual disturbances, tinnitus, tremor, and/or paraesthesia. Infrequent ADRs associated with the use of lidocaine include: hypotension, bradycardia, arrhythmias, cardiac arrest, muscle twitching, seizures, coma, and/or respiratory depression.
This article uses material from the Wikipedia article Lidocaine topical, which is released under the Creative Commons Attribution-Share-Alike License 3.0.