Objectives: The therapeutic efficacy of topical drugs is related to their ability to penetrate through the stratum corneum, which is a hydrophobic and brick and mortar barrier structure. To enhance drug bioavailability, several chemical or physical strategies have been recently advocated to enhance drug delivery at deeper skin layers so as to reach target cells
Introduction: In recent studies, for Mal or steroids, among all techniques, drug delivery was most enhanced after AFXL CO2 pretreatment, followed by sandpaper abrasion and microneedling (it seems that the coagulation zone thickness around microchannels impacts the degree of absorption).
Laser settings must be adapted to each specific indication: low fluence (5-10 mJ/MTZ) and low density (5%) are recommended for MAL laser CO2 assisted delivery on the face and the scalp.
Materials / method: In daily practice, optimal channel width, depth and density would vary according to various factors: indication, patient and area of the body being treated (thickness of the lesion or of the intact stratum corneum or nail…, age, gender, ethnicity…) & molecule being delivered (molecular weight, charges, hydrophily…). Other practical key points:
- vehicle of the drug: liquid and gel formulations penetrate laser channels more readily than cream formulations
- Timing of application: Skin uptake increases within the first 6 hours, and is greatest within 30 minutes after laser exposure
Results: Emergent risks can be expected and some have already been reported: Infection (non sterile preparation, occlusion, erosion as for 5-FU… ); systemic absorption and toxicity (poisoning with lidocaïne); intensified local cutaneous adverse effects of the drug (MAL: phototoxicity, delayed wound healing… , steroids: atrophy, hypochromia, 5-FU, IMQ, MTX : pain, erosion, hyperpigmentation, wounds, scars…); immunogenicity: local or systemic hypersensitivity reactions due to the introduction of immunogenic particles into the dermis, carcinogenicity (hydroquinone?, excipients?), teratogenicity
Conclusion: Our advice in 2019:
- Use of products suited for intradermal injections or topical products in as pure a formulation as possible
- Treat only localized body surface areas (respect contraindications of each drug delivered, ex. pregnancy or desire of pregnancy…)
- Use of drug doses not higher than those administered during intra-dermal injections
- Use only specific non allergenic care products after those procedures
Main reference
Pr Haedersdal M, Dover JS et al.
Challenges to Laser-Assisted Drug Delivery : Applying Theory to Clinical Practice
Lasers Surg Med 2018 Jan
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