LIDOCAINE 2%W/V INJECTION

Indications

• Local anesthesia for surgical procedures
• Regional anesthesia (e.g., epidural anesthesia)
• Management of acute ventricular arrhythmias
• Topical anesthesia for minor skin procedures

Dosage

Children: Refer to the BNF for Children for

Adults: For local anesthesia, the typical dosage depends on the procedure and formulation, generally ranging from 1% to 2% solutions. For antiarrhythmic use, initial intravenous doses may be 1 to 1.5 mg/kg, with subsequent doses as needed. Refer to specific guidelines for detailed dosing.

Mechanism of action

Lidocaine exerts its effects by blocking voltage-gated sodium channels in neuronal membranes. This inhibition prevents the initiation and conduction of nerve impulses, leading to a local anesthetic effect. By stabilizing the neuronal membrane, lidocaine decreases the excitability of the nerve fibers, effectively preventing pain signals from being transmitted to the brain.

Pharmacodynamics

Lidocaine produces a dose-dependent effect, meaning that higher concentrations yield more profound anesthesia. The onset of action typically occurs within a few minutes of administration, and the duration of anesthesia can last from 30 minutes to several hours, depending on the formulation and route of administration. Additionally, lidocaine has antiarrhythmic properties, as it can normalize the electrical activity of the heart by stabilizing the cardiac cell membrane.

Pharmacokinetics

Lidocaine is well absorbed when administered via various routes including intravenous, topical, and local infiltration. After systemic administration, it is rapidly distributed throughout the body, with a volume of distribution approximately 1 to 2 L/kg. The drug is primarily metabolized in the liver by cytochrome P450 enzymes, mainly CYP1A2 and CYP3A4, into active metabolites. The elimination half-life ranges from 1.5 to 2 hours, with renal excretion of metabolites being the primary route of elimination.

Contra-indications

• Hypersensitivity to lidocaine or any component of the formulation
• Severe heart block
• Adams-Stokes syndrome
• Porphyria

Adverse effects

• Hypotension
• Bradycardia
• Dizziness
• Tinnitus
• Nausea
• Vomiting
• Allergic reactions
• Seizures
• Cardiac arrest

Interactions

• CYP1A2 inducers and inhibitors may alter lidocaine metabolism
• Caution with other local anesthetics due to additive toxicity
• May enhance the effects of neuromuscular blockers

Precautions

• Use with caution in patients with liver dysfunction
• Caution in patients with heart disease or hypotension
• Monitor for signs of toxicity, especially in elderly patients

Pregnancy

Lidocaine is classified as category B. It is generally considered safe during pregnancy, but should be used only if clearly needed.

Breast-feeding

Lidocaine is excreted in breast milk in small amounts. It is considered safe for use during breastfeeding.

Storage

Store at room temperature, away from light and moisture. Protect from freezing.

Formulations

• Injectable solution
• Topical gel
• Transdermal patch
• Ointment
• Cream