📋 Clinical Overview

Lidocaine 15% w/w is a high-potency topical amide local anesthetic, primarily formulated as a patch or medicated plaster. It is indicated for the treatment of post-herpetic neuralgia (PHN) and other localized neuropathic pain conditions. It works by stabilizing neuronal membranes and inhibiting the ionic fluxes required for the initiation and conduction of nerve impulses, specifically by blocking voltage-gated sodium channels.

💊 Dosage & Administration

Adult: Apply up to 3 patches (or the equivalent in plaster size) to the most painful area(s) for up to 12 hours within a 24-hour period. Patches may be cut to size before removal of the release liner. Do not reapply for at least 12 hours after removal.

Note: 1. Apply to intact, dry, non-hairy skin. 2. Clip hair, do not shave. 3. Apply patch to area of maximum pain. 4. Wear for up to 12 hours, then remove. 5. Allow skin to rest for 12 hours before next application. 6. Wash hands after handling. 7. Do not apply with external heat sources.

⚠️ Contraindications

Known hypersensitivity to lidocaine, other amide-type local anesthetics, or any component of the patch/plaster.
Application to broken, inflamed, or non-intact skin (unless specifically indicated for a formulation designed for such use).
Severe hepatic impairment (Child-Pugh Class C).

🔬 Mechanism of Action

Lidocaine acts by blocking voltage-gated sodium channels (NaV channels, particularly NaV1.7, NaV1.8) on the neuronal cell membrane. This blockade inhibits the transient influx of sodium ions (Na+) necessary for the depolarization phase of the action potential. By preventing depolarization, it halts the initiation and propagation of nerve impulses, leading to a reversible loss of sensation (analgesia) in the localized area.

🤕 Side Effects

Application site reactions: Erythema (redness), rash, itching, burning sensation
Localized edema
Abnormal skin sensation (numbness)

🤰 Special Populations

Pregnancy: Category B (US FDA). No well-controlled studies in pregnant women. Use only if clearly needed. Systemic absorption is low with proper use.

Driving: May cause dizziness, drowsiness, or blurred vision. Patients should be cautioned about operating machinery or driving until they know how the medication affects them.

🔄 Drug Interactions

Class I Antiarrhythmics (e.g., Mexiletine, Tocainide)	Additive cardiac toxicity; increased risk of arrhythmia.	Major
CYP1A2 & CYP3A4 Inhibitors (e.g., Ciprofloxacin, Fluconazole, Amiodarone)	Increased lidocaine plasma levels, risk of systemic toxicity.	Moderate
Other Local Anesthetics	Additive toxic effects.	Major
Beta-blockers (e.g., Propranolol)	May reduce hepatic blood flow, increasing lidocaine levels.	Moderate

Lidopatch