Lidocaine (INN) or lignocaine (former BAN) is a popular local anesthetic often used in dentistry or topically. It is marketed by AstraZeneca under the brand name Xylocaine.
History
Lidocaine, the first amide-type local anesthetic, was developed by Nils Lofgren in 1943 and first marketed in 1948.
Pharmacology
Lidocaine is metabolized in the liver and excreted by the kidneys.
It is faster acting and longer lasting than procaine (novocaine).
When given intravenously, lidocaine is a class Ib antiarrhythmic agent and will block the sodium channel of the cardiac action potential, which decreases automaticity by reducing the slope of phase 4 depolarization with little effect on the PR interval , QRS complex or QT interval.
This drug is used in the treatment of ventricular cardiac arrhythmias and cardiac arrest with ventricular fibrillation, especially with acute ischemia, though it is not useful in the treatment of atrial arrhythmias.
The half life of intravenous lidocaine is about 109 minutes, but because it is metabolized in the liver (which depends on liver blood flow), dosage should be reduced in patients with low cardiac output or who are in shock.
In patients with cardiogenic shock, the half life may exceed ten hours.
Toxicity
Toxicity is most often seen when there has been an inadvertent intravascular injection of lidocaine when being used as a local anesthetic.
Central nervous system toxicity manifests as diziness, paresthesia (pins and needles), confusion and – in more severe cases – seizures or coma.
Severe toxicity may also result in cardiovascular system collapse or asystole.
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