1. Introduction
Lidocaine is a local anaesthetic and antiarrhythmic drug widely used for pain relief and to manage abnormal heart rhythms. It works by blocking sodium channels, stabilising neuronal and cardiac cell membranes, and reducing nerve signal transmission or abnormal electrical activity.
2. Indications
- Approved Indications:
- Local anaesthesia (infiltration, nerve block, epidural).
- Topical anaesthesia (minor procedures or pain relief).
- Ventricular arrhythmias (e.g., during myocardial infarction).
- Postherpetic neuralgia (topical patch).
- Off-Label Uses:
- Neuropathic pain (topical use).
- Pain management in minor burns or wounds.
3. Dosage
- Local Anaesthesia:
- Infiltration: 0.5%–1% solution, up to 300 mg per dose (with epinephrine, maximum 500 mg).
- Nerve block: 1%–2% solution, dose varies by site and procedure.
- Topical Anaesthesia:
- Gels/creams (e.g., 2%–5%): Apply a thin layer to the affected area up to 3–4 times daily.
- Lidocaine patches (5%): Apply one patch to the affected area daily for up to 12 hours.
- Antiarrhythmic:
- IV bolus: 1–1.5 mg/kg over 2–3 minutes.
- IV infusion: 1–4 mg/min, adjusted based on response and ECG monitoring.
- Paediatrics:
- Dose varies based on weight and indication; consult specialist guidance.
4. Administration
- Local/Topical Use: Apply directly to the target area or administer via infiltration/nerve block.
- IV Use: Administer under continuous ECG monitoring in a hospital setting.
5. Forms Available
- Injection: 0.5%, 1%, 2% solutions (with or without epinephrine).
- Topical: Creams, gels, sprays (2%–10%), 5% patches.
- IV: 1% and 2% solutions for antiarrhythmic use.
6. Side Effects
6.1. Common Side Effects
- Local irritation or redness (with topical use).
- Numbness or tingling at the application site.
- Dizziness or light-headedness (with systemic use).
6.2. Less Common Side Effects
- Metallic taste (systemic absorption).
- Nausea.
- Tremors or restlessness.
6.3. Rare but Serious Side Effects
- Seizures (from systemic toxicity).
- Cardiovascular collapse or arrhythmias.
- Methemoglobinaemia.
- Allergic reactions (e.g., rash, swelling).
7. Warnings
- Systemic Toxicity (LAST): Local anaesthetic systemic toxicity (LAST) can occur with excessive dosing or rapid systemic absorption. Signs include seizures, cardiac arrest, and CNS depression.
- Methemoglobinaemia: Risk increases with large doses, especially in infants and patients with G6PD deficiency.
- Cardiac Effects: Prolonged or excessive use may cause bradycardia or arrhythmias.
8. Precautions
- Use cautiously in:
- Patients with severe liver disease (reduced metabolism of lidocaine).
- Elderly patients (increased risk of toxicity).
- Patients with cardiac conduction abnormalities.
- Avoid applying topical lidocaine to broken skin or mucous membranes.
9. Interactions
- Drug-Drug Interactions:
- Beta-blockers: May increase plasma levels of lidocaine due to reduced clearance.
- CYP3A4 inhibitors (e.g., erythromycin, ketoconazole): May increase lidocaine toxicity.
- Class I antiarrhythmics (e.g., procainamide): Additive cardiac depressant effects.
- Drug-Food Interactions:
- None significant.
10. Monitoring Parameters
- For local use: Watch for signs of irritation or allergic reactions.
- For systemic use: Monitor ECG, blood pressure, and signs of CNS toxicity (e.g., confusion, seizures).
- Plasma lidocaine levels (if prolonged infusion or high doses).
11. Use in Children
- Safe for local and topical use in children, but dose adjustments are required based on weight.
- Avoid high doses or large surface applications due to increased risk of systemic absorption.
12. Use in Pregnancy
- Category B: Generally safe for local anaesthesia during pregnancy. Topical and injectable forms can be used with caution.
13. Use in Elderly
- Start with lower doses due to decreased hepatic metabolism and increased sensitivity to side effects.
14. Use in Kidney Disease
- No specific dose adjustments required, but monitor for toxicity in severe renal impairment.
15. Use in Liver Disease
- Use cautiously in patients with severe liver disease, as lidocaine is metabolised in the liver. Reduce dose if necessary.
16. Patient Counselling Points
- For topical use: Apply only to intact skin and follow dosing instructions. Avoid covering the area with tight dressings.
- For local anaesthesia: Inform your doctor of any unusual numbness or persistent tingling.
- Report symptoms of toxicity, such as confusion, dizziness, or irregular heartbeat.
- Avoid eating or drinking immediately after lidocaine use in the mouth or throat to prevent choking.
- Keep out of reach of children to prevent accidental ingestion or misuse.
17. Table of Brand Names, Manufacturers, and Prices
Brand Name | Manufacturer | Price (USD) |
---|---|---|
Xylocaine (Injection) | AstraZeneca | $10–20 (10 mL, 1% solution) |
Lidoderm (Patch) | Endo Pharmaceuticals | $250–400 (30 patches, 5%) |
Generic Lidocaine | Various manufacturers | $5–15 (10 mL, 1% solution) |
18. FAQs (15 Questions)
- What is lidocaine used for?
It is used for local anaesthesia, pain relief, and managing ventricular arrhythmias. - How does lidocaine work?
It blocks sodium channels, reducing nerve signal transmission and stabilising cell membranes. - How long does lidocaine last?
Effects of local anaesthesia typically last 1–2 hours, depending on the dose and site. - Can lidocaine be used during pregnancy?
Yes, it is generally safe when used as directed for local anaesthesia. - What are common side effects of lidocaine?
Common side effects include local irritation, numbness, and dizziness. - Can lidocaine cause toxicity?
Yes, excessive dosing or rapid absorption can cause systemic toxicity, including seizures or cardiac arrest. - Is lidocaine safe for children?
Yes, but doses must be adjusted based on weight and age. - Can lidocaine be used for burns?
Yes, it can provide pain relief for minor burns, but avoid applying to large or broken skin areas. - How is lidocaine administered?
It can be applied topically, injected locally, or infused intravenously for specific indications. - Can I use lidocaine patches daily?
Yes, but apply for no more than 12 hours in a 24-hour period. - Does lidocaine interact with other medications?
Yes, interactions can occur with beta-blockers, CYP3A4 inhibitors, and other antiarrhythmics. - Can I drive after using lidocaine?
Avoid driving if you experience dizziness, drowsiness, or other side effects. - What should I do if I apply too much lidocaine?
Seek medical attention immediately if you experience symptoms like seizures, confusion, or irregular heartbeat. - Can lidocaine cause allergic reactions?
Yes, although rare, allergic reactions such as rash, itching, or swelling may occur. - How should lidocaine be stored?
Store at room temperature, away from light and moisture.