Lidocaine + Prilocaine

Approved Indications:

• Topical Anesthesia on Intact Skin:
• For needle insertions (e.g., intravenous cannulation, blood sampling).
• For minor dermatological procedures (e.g., wart removal, laser therapy).
• Topical Anesthesia on Genital Mucosa:
• Before minor surgical procedures (e.g., circumcision, superficial genital surgery).
• Topical Anesthesia of Leg Ulcers:
• For cleaning or debridement procedures.

Clinically Accepted Off-label Uses:

• Pre-procedure analgesia before cosmetic interventions (e.g., microneedling, laser resurfacing, dermal fillers).
• Pain relief prior to tattoo application or removal.

Adults:

• On Intact Skin: Apply 1–2 g per 10 cm² area. Leave under occlusion for at least 1 hour, up to 5 hours maximum.
• On Genital Mucosa: Apply 5–10 g for 5–10 minutes, no occlusion needed.
• Max Dose: Do not exceed 10 g or apply over more than 100 cm² of skin.

Pediatric Use:

• Up to 3 months: 1 g over 10 cm², max 1 hour.
• 3–12 months: 2 g over 20 cm², max 1 hour.
• 1–6 years: 10 g over 100 cm², up to 2 hours.
• 7–12 years: 10 g over 100 cm², up to 5 hours.

Elderly:

• Same as adult dosing. Monitor for systemic absorption.

Special Populations:

• Hepatic/Renal Impairment: Use with caution. Monitor for toxicity. Reduce area and duration.

Route: Topical only (skin/mucous membranes). Avoid contact with eyes or ears.

Lidocaine and prilocaine are amide-type local anesthetics that reversibly block voltage-gated sodium channels in neuronal cell membranes. This inhibition prevents depolarization and conduction of nerve impulses, leading to localized loss of sensation. The combination provides a synergistic anesthetic effect with a faster onset and longer duration of action when applied to intact skin or mucosa.

• Absorption: Limited on intact skin; higher through mucous membranes or broken skin.
• Bioavailability: ~3% for intact skin, higher on mucosa.
• Onset of Action: 1 hour on skin; 5–10 minutes on mucosa.
• Peak Plasma Concentration: Within 2–6 hours after application.
• Distribution: Widely distributed; moderate plasma protein binding.
• Metabolism:
• Lidocaine: Liver via CYP1A2 and CYP3A4.
• Prilocaine: Primarily in liver and kidneys.
• Elimination Half-Life:
• Lidocaine: ~1.5–2 hours.
• Prilocaine: ~1.5 hours.
• Excretion: Renal (as metabolites).

• Pregnancy: Category B. No fetal harm in animal studies; limited human data. Use only if clearly needed.
• Lactation: Excreted in breast milk in minimal amounts. Safe when used in small areas for short duration.
• Caution: Avoid extensive use on large areas during pregnancy or lactation.

• Primary Class: Local Anesthetic
• Subclass: Amide-type combination topical anesthetic

• Known hypersensitivity to lidocaine, prilocaine, or other amide-type anesthetics
• Congenital or idiopathic methemoglobinemia
• Use on large surface areas in infants <12 months, especially with concurrent methemoglobin-inducing agents
• Application on broken or inflamed skin (unless specifically indicated)

• Methemoglobinemia Risk: Increased in neonates, G6PD-deficient patients, and those on oxidizing agents (e.g., sulfonamides).
• Hepatic Impairment: May increase risk of toxicity due to impaired metabolism.
• Cardiac Patients: Use cautiously due to systemic absorption potential.
• Avoid Use in Eyes or Ears: Not for ophthalmic or otic use.
• Prolonged Exposure: Avoid excessive dosage, prolonged application, or large surface areas.

Common (Localized):

• Redness, blanching, swelling, itching, or burning at the application site
• Mild skin irritation or rash

Serious/Rare:

• Methemoglobinemia (cyanosis, dizziness, fatigue)
• Allergic reactions (urticaria, angioedema, anaphylaxis)
• Systemic CNS effects (drowsiness, seizures) with overdose or misuse

Onset: Local effects typically occur within 1–3 hours; systemic toxicity is rare with proper use.

• Oxidizing Agents (e.g., dapsone, nitrates, sulfonamides): ↑ risk of methemoglobinemia
• Other Local Anesthetics: Additive toxicity if co-applied
• CYP450 Inhibitors: May affect lidocaine metabolism
• Beta-blockers or cimetidine: May decrease hepatic clearance of lidocaine

No significant food or alcohol interactions for topical use.

• EMA/FDA: Reinforced warnings on methemoglobinemia risk in infants <12 months.
• Clinical Practice Updates: Reaffirmed safe use in pediatric and cosmetic settings when guidelines are followed.
• New Labeling: Clarified dosing limits for neonates and extended use warnings.

• Temperature: Store below 25°C (77°F)
• Humidity: Keep in a dry place, tightly closed
• Light: Protect from light
• Handling: Do not freeze. Shake tubes gently before use.
• Reconstitution: Not applicable
• Shelf Life: Follow label; typically 2–3 years unopened