The purpose of this study is to assess the clinical efficacy of fractional CO2 laser-assisted delivery of a topically applied anesthetic to the perceived pain during filler injection.

Rationale: In daily practice, common aesthetic and laser procedures of the face are carried out under local anesthesia using topical formulations. This procedure is time-consuming, as the anesthetic has to be applied at least one hour before treatment, and is often only partially effective, especially on the face due to increased pain perception. The other option, of infiltration of an anesthetic solution, though effective, is often associated with discomfort, and is not favored during facial procedures (due to changes of the facial landmarks), while it is not tolerated by patients who have needle phobia. In the past years, enhanced and accelerated penetration of various topically applied substances, including photosensitizers, has been proven by pretreatment of the skin with a fractional laser, creating a pattern of microscopic ablation craters. There is also evidence that transdermal anesthetic cream absorption can be increased by fractional laser pretreatment. These outcomes might suggest that adequate local anesthesia may be achieved by applying an anesthetic drug topically on a skin surface pretreated with a fractional laser. However, little is known about the role and efficacy of the fractional laser on topical anesthetic delivery in the clinical setting of facial fillers injection.

Objective: The primary objective of this study is to assess the analgesic effect of fractional carbon dioxide laser-assisted delivery of a topical anesthetic cream (mixture of lidocaine and tetracaine) compared to the application of this anesthetic without fractional laser pretreatment.

Study design: Prospective, double-blinded, randomized, controlled, within subject, study.

Study population: 21 healthy volunteers ≥18 years, who give written informed consent Intervention: In each subject, each cheek region of the subject will be randomly allocated to (1) ablative fractional laser (AFL) pretreatment (5% density, 2.5 mJ/microbeam) followed by topical application of local anesthetic or (2) sham AFL followed by application of local anesthetic. Sham AFL will be done by delivering an AFL pass at the same 5% density and 2.5 mJ/microbeam right adjacent to the region of local anesthetic application on the cheek. After ten minutes incubation time, the typical filler injections procedure will be performed, through the same always entry points.

Subjects will be asked to indicate pain on a visual analogue scale (VAS) from 0-10 (0: no pain; 10: worst imaginable pain) directly after treatment completion.

Inclusion Criteria:

• Age ≥18 years
• Patient is willing and able to give written informed consent
• Patient asks for facial filler injections (hyaluronic acid) to improve the facial aesthetic/ aging signs

Exclusion Criteria:

• History of keloid or hypertrophic scar formation or complicated wound healing
• Presence of any active skin disease
• Known allergy to local anesthesia
• Pregnancy or lactation
• Incompetency to understand what the procedure involves
• Current complaints of chronic pain or other alterations in pain sensation (e.g. due to diabetes mellitus or lepra)
• Current treatment with systemic analgesics or other medication that can influence pain sensation
• Current treatment with anticoagulants