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Monday, July 28, 2025

Lidocaine skin cream


Generic Name: Lidocaine (topical)
Drug Class: Local anesthetic – amide type
Pharmacological Class: Sodium channel blocker (local anesthetic)
ATC Code: D04AB01
Regulatory Status: Over-the-counter (OTC) at low strengths (≤4%); prescription-only at higher strengths and in combination formulations
Common Brand Names: LMX, Emla (with prilocaine), Xylocaine Topical, Lidoderm (patch), AneCream, Topicaine, LidaMantle

Mechanism of Action

Lidocaine is an amide-type local anesthetic that works by reversibly blocking voltage-gated sodium channels on neuronal cell membranes. This:

  • Prevents the initiation and propagation of action potentials

  • Interrupts nerve signal transmission from the periphery to the central nervous system

  • Results in localized numbness or analgesia

When applied to intact or broken skin, lidocaine penetrates the epidermis and dermis to act on superficial nociceptors.

Therapeutic Indications

Lidocaine skin cream is indicated for temporary topical anesthesia of the skin and mucous membranes. Typical clinical uses include:

  1. Relief of Local Pain or Itching:

    • Minor cuts, abrasions, insect bites, sunburn

    • Eczema, dermatitis, and anal/rectal irritation (e.g., hemorrhoids)

    • Genital or perianal discomfort

  2. Pre-procedural Anesthesia:

    • Needle insertion (venipuncture, cannulation, vaccinations)

    • Minor dermatological procedures (e.g., laser therapy, skin biopsy)

  3. Burns (minor first-degree):

    • Reduces discomfort by numbing damaged tissue

  4. Post-herpetic Neuralgia (off-label, or as part of patch therapy)

  5. Cosmetic Procedures:

    • Numbing skin before aesthetic treatments (e.g., microdermabrasion, tattooing, laser hair removal)

  6. Combination Use (e.g., Emla Cream):

    • Lidocaine + prilocaine combo used for deeper dermal anesthesia, e.g., circumcision, minor surgery

Formulations and Strengths

  • Lidocaine 2% cream (Rx, common for medical use)

  • Lidocaine 4% cream (OTC, widely used for self-treatment)

  • Lidocaine 5% cream (Rx, stronger concentration for clinical use)

  • Combination products:

    • Emla cream (Rx): Lidocaine 2.5% + Prilocaine 2.5%

    • Other anesthetic mixtures: May contain tetracaine, benzocaine, or epinephrine

Other forms include:

  • Ointments

  • Gels

  • Sprays

  • Lotions

  • Patches (e.g., Lidoderm 5%)

Dosage and Administration

Application Guidelines:

  • Apply thin layer to the affected or targeted area of skin

  • Frequency: Up to 3–4 times daily depending on product strength and clinical need

  • Do not exceed manufacturer-recommended maximum dose or surface area coverage

  • Occlusive dressings may be used (e.g., with Emla) to enhance absorption prior to procedures

For pre-procedure anesthesia:

  • Adults and children >12 years:

    • Apply 2.5–5 g of cream to 20–25 cm² skin area

    • Cover with occlusive dressing

    • Leave in place for 30–60 minutes before procedure

    • Duration of anesthesia: ~1–2 hours after removal

Pharmacokinetics (Topical)

  • Onset: 15–60 minutes depending on formulation and skin condition

  • Duration: 30 minutes to several hours

  • Absorption: Depends on dose, skin integrity, surface area, and presence of occlusion

  • Metabolism: Hepatic (via CYP1A2 and CYP3A4)

  • Elimination: Renal, as metabolites

Systemic absorption is usually minimal when applied to intact skin but may increase significantly with:

  • Broken or inflamed skin

  • Large surface area application

  • Use in infants or elderly

  • Occlusive dressing

Contraindications

  • Hypersensitivity to lidocaine or other amide-type local anesthetics

  • Skin infections or severe dermatological disease at site of application

  • Use on mucous membranes unless product is specifically approved for such use

  • Children <2 years (for certain high-strength or occluded formulations)

Special Warnings and Precautions

  1. Methemoglobinemia Risk:

    • Rare but serious condition; higher risk in neonates, patients with G6PD deficiency, or when combined with other oxidizing drugs (e.g., prilocaine)

  2. Systemic Toxicity (in overdose):

    • CNS: confusion, drowsiness, seizures, coma

    • Cardiovascular: bradycardia, hypotension, arrhythmias, cardiac arrest

  3. Broken or Inflamed Skin:

    • Increases absorption and systemic toxicity risk; apply with caution

  4. Pediatric Caution:

    • Topical anesthetic use in infants/young children must be guided by a physician

  5. Contact with Eyes or Mucosa:

    • Avoid; may cause severe irritation or corneal injury

Adverse Effects

Common (≥1%):

  • Local burning or stinging sensation

  • Erythema or blanching at application site

  • Mild edema

  • Skin irritation or rash

Uncommon:

  • Allergic contact dermatitis

  • Drowsiness or dizziness (with large application)

Rare/Serious:

  • Methemoglobinemia

  • Systemic CNS or cardiac toxicity

  • Anaphylactic reaction (extremely rare)

Drug Interactions

  • Class 1 antiarrhythmics (e.g., mexiletine, tocainide): Additive effects

  • Beta-blockers (e.g., propranolol): May increase systemic lidocaine levels

  • Cimetidine: Reduces hepatic clearance; increases plasma levels (clinically relevant with large doses or hepatic impairment)

  • Prilocaine or benzocaine: Additive methemoglobinemia risk when used together

Use in Pregnancy and Lactation

Pregnancy:

  • Category B (US FDA): No evidence of fetal harm; use if clearly needed

  • Widely used in obstetric and gynecological procedures

Lactation:

  • Excreted in breast milk in small amounts

  • Safe for topical use in breastfeeding mothers; avoid nipple application unless specifically prescribed

Overdose and Toxicity

Symptoms:

  • CNS excitation (tremors, seizures), followed by depression (drowsiness, coma)

  • Bradycardia, hypotension

  • Methemoglobinemia (gray-blue skin, cyanosis, fatigue)

Management:

  • Discontinue drug

  • Symptomatic and supportive care

  • Seizures: Treated with benzodiazepines (e.g., diazepam)

  • Cardiac support: Fluids, vasopressors

  • Methemoglobinemia: Treated with IV methylene blue

Monitoring Parameters

  • Clinical response (pain relief, numbness)

  • Signs of local skin reaction

  • Signs of systemic toxicity in high-risk or pediatric patients

  • Methemoglobin levels if cyanosis or suspected toxicity

Storage and Handling

  • Store at 15–30°C (59–86°F)

  • Protect from light and freezing

  • Keep out of reach of children

  • Follow expiration dates strictly; potency and safety may diminish over time

Patient Counseling Points

  • Apply only to clean, dry, intact skin unless advised by a healthcare provider

  • Wash hands before and after application

  • Do not use on large areas or for prolonged periods without medical advice

  • Avoid contact with eyes, mouth, and open wounds

  • Do not occlude the area unless instructed (especially with infants or young children)

  • Discontinue and report rash, swelling, or systemic symptoms

  • Follow labeled dosage instructions strictly, especially with OTC products

  • Consult physician if symptoms persist or worsen after a few days



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