Topical Anesthetics in Dermatologic Procedures

Background

  • Increasing use of topical anesthetics by clinicians to decrease pain during minimally invasive dermatologic procedures.
  • Crucial for clinicians to understand indications, contraindications, pharmacological mechanisms, and applications of commonly used topical anesthetics.

Regulations (Australia)

  • Regulated nationally by the Therapeutic Goods Administration (TGA).
  • Also regulated in South Australia under the Controlled Substance Act 1984.
  • Users must be aware of their legal responsibilities and potential hazards related to topical anesthetics.

Labelling of Scheduled Medicines

  • Medicines registered for use in Australia are labelled as:
    • Pharmacy Medicine
    • Pharmacist Only Medicine
    • Prescription Medicine
  • Medicines accepted by the TGA have either an AUST R number or AUST L number on the label.
  • Refer to the Australian Register of Therapeutic Goods (ARTG) to verify lawful supply.

Classification of Medications

  • Schedule 2 - Pharmacy Medicines:
    • Available for purchase in a pharmacy.
    • Example: Numbing creams with 10% or less lidocaine (lignocaine).
  • Schedule 4 - Prescription Only Medicines:
    • Available from a pharmacist only with a doctor's prescription.
    • Example: Numbing creams with more than 10% lidocaine (lignocaine).

Regulation

  • Topical anesthetics used to numb pain in skin procedures fall under Schedule 2 Medicines in Australia.
  • Restrictions apply to their use.
  • Anything compounded or over 10% (combined) requires a doctor's prescription (Schedule 4 medication).
  • Tattoo artists, dermal therapists, and laser technicians cannot supply Schedule 4 medicines.

Selling of Scheduled Medications

  • Only authorized or licensed individuals under the Controlled Substances Act 1984 can sell or supply scheduled medicines.
  • Administration must be in accordance with the Act.
  • Illegal sale, supply, or administration is an offense under the Controlled Substance Act 1984.
    • Maximum penalty: 10,00010,000 or imprisonment for 2 years.

Common Cosmetic Procedures Where Topical Anesthetics Might Be Used

  • Lasers
  • Cosmetic Injectable procedures
  • Skin Needling
  • Dermabrasion
  • Tattoo Removal
  • Tattooing
  • Body piercing
  • Veni-Puncture
  • Excisions and Subcisions

Active Ingredients

  • Lidocaine (also called lignocaine)
  • Prilocaine
  • Tetracaine
  • Benzocane

Anaesthetics Mechanism of Action

  • Reversibly block nerve conduction near the administration site.
  • Cause temporary loss of sensation in a limited area.
  • Decrease nerve cell membrane permeability to sodium ions.
  • Possibly compete with calcium-binding sites that control sodium permeability.
  • Result in decreased depolarization and increased excitability threshold.
  • Prevents nerve action potential from forming.

Absorption

  • Variable absorption superficially via intact skin.

Increasing Absorption

  • Liposomal preparations
  • Iontophoresis
  • Transdermal patches
  • Occlusion

Factors to Consider

  • Heat may increase or reduce anesthetic penetration.
  • Heat can cause vasodilatation, enhancing systemic absorption and increasing toxicity.
  • Occlusion increases permeability by raising temperature and hydration of the stratum corneum.

Dosage Guidelines

  • Careful attention to:
    • Anatomic location
    • Total surface area covered
    • Duration of anesthetic skin contact
  • Apply a thin layer (approximately 2mm thick) across the area identified for numbing.

Caution

  • Topical anesthetic agents are generally effective and safe for dermatologic procedures with low risk of adverse events.
  • However, caution is necessary when using occlusion or treating large surface areas.
  • Particular caution should be exercised with compounded mixtures and non-standard doses due to increased risk of adverse events and even death.

Contraindications

  • Applying large amounts to large surface areas, or irritated/damaged skin can lead to high anesthetic concentrations in the bloodstream, causing serious side effects or toxicity.
  • Actual hypersensitivity is rare (less than 1% of reactions).
  • Allergic reactions may be due to acute toxicity, concurrent drug therapy (e.g., tachycardia from epinephrine), or preservatives (e.g., parabens or sulfites).

Contraindications (Specific)

  • Allergies to anesthetics
  • Known cardiovascular concerns
  • Client already on adrenaline (requires clearance by a medical doctor)
  • Broken skin (Kouba, et al., 2016)

Potential Complications (Kouba, et al., 2016)

  • Usually caused by high plasma concentrations of topical anesthetics due to excessive exposure following a tear in the skin.
  • Burning or stinging
  • Seizures
  • Respiratory arrest
  • Bradycardia
  • Skin discoloration
  • Swelling
  • Arrhythmia
  • Hypotension
  • Cardiovascular issues
  • Death

Adverse Events

  • If a patient experiences side effects:
    • Refer immediately to your protocol doctor.
    • Call 000 in case of:
      • Seizures
      • Respiratory arrest
      • Bradycardia
      • Arrhythmia
      • Hypotension