What Is Lidocaine?
Lidocaine is a white to slightly yellowish crystal or powder.
It is insoluble in water, but soluble in methanol and ethanol. It is also soluble in dilute hydrochloric acid. Lidocaine hydrochloride (C14H22N2O・HCl), which is made by dissolving lidocaine in a specific proportion to dilute hydrochloric acid (HCl), is commonly used as an injectable drug.
It has a pharmacological action, binding to sodium channels in the neuronal cell membrane, and inhibiting the permeation of sodium ions. This inactivates the action potential and blocks neurotransmission.
Uses of Lidocaine
Lidocaine is used medicinally for its pharmacological effects, namely for local anesthesia and suppression of arrhythmias.
Lidocaine preparations with varying concentrations from 0.5% to 2% are distributed as local anesthetics. If used in excess of the dosage, there is a risk of side effects, such as causing convulsions or affecting the myocardium.
Properties of Lidocaine
Lidocaine is easily soluble in acetic acid and diethyl ether. Because it is insoluble in water, lidocaine hydrochloride (C14H22N2O・HCl) is mixed with dilute hydrochloric acid for intravenous use. Lidocaine hydrochloride injection is an aqueous, clear, colorless liquid.
Structure of Lidocaine
Lidocaine’s chemical formula is C14H22N2O and its molecular weight is 234.34. Lidocaine hydrochloride, commonly used as an injectable drug, has the chemical formula C14H22N2O-HCl and a molecular weight of 270.8.
Other Information on Lidocaine
1. Local Anesthetic Action of Lidocaine
Lidocaine is an amide local anesthetic developed by Swedish chemists Nils Löfgren and Bengt Lundqvist.
2. Comparison of Lidocaine and Tetracaine
Lidocaine is slightly inferior to tetracaine, which is considered the most potent local anesthetic, in terms of potency and duration of action. However, lidocaine has generally been used because it is less toxic than tetracaine and has sufficient medicinal properties. It is also used in combination with tetracaine as a mixture.
Xylocaine (lidocaine) solutions for local anesthesia contain epinephrine (adrenaline), which is a vasoconstrictor. This helps to prolong the anesthetic effect and also has a hemostatic effect, limiting the amount of bleeding.
3. Comparison of Lidocaine and Procaine
Compared to procaine, lidocaine is more liposoluble and protein-binding, and has a longer anesthetic action and duration. To prolong its duration of action, it is used in combination with adrenaline. However, there are some sites where adrenaline cannot be used in combination, such as fingertips, because it can cause irreversible necrosis.
4. Pharmacological Effects of Lidocaine
Lidocaine binds to sodium channels and blocks neurotransmission by inhibiting the permeation of sodium ions, so it inactivates the action potential. Sodium channels, a type of ion channel, are also involved in cardiac rhythm and can therefore be used to treat arrhythmias.
Specifically, 0.5%, 1%, and 2% Lidocaine preparations are commercially available as local anesthetics. It can be used for surface anesthesia, transfer anesthesia, infiltration anesthesia, spinal anesthesia, and epidural anesthesia.
As an antiarrhythmic agent, lidocaine falls into group Ib of the Bourne-Williams classification. This group, with the exception of aprindine, is indicated only for ventricular arrhythmias. In addition, lidocaine is available over the counter as a topical and nasal solution for antipruritic use.