The purpose of this study is to assess the efficacy of fractional CO2 laser assisted delivery of topically applied anesthetics (articaine hydrochloride 40 mg/ml and epinephrine 10 μg/ml solution and EMLA cream) regarding to anesthesia of the skin.

Rationale: In dermatology, many minor surgical and laser procedures are carried out under local anesthesia of the skin. Anesthesia using topical formulations is time consuming, as the anesthetic has to be applied at least one hour before treatment, and is often only partially effective. On the other hand infiltration anesthesia is often associated with discomfort and is not tolerated by patients who are for example needle phobic. 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.(Haedersdal et al., 2010) This improvement in drug penetration seems to be regardless of ablation crater depth.(Haak et al., 2012) There is limited evidence that transdermal lidocaine absorption can be increased by fractional laser pretreatment.(Oni et al., 2012; Oni et al., 2013) These findings might suggest that local anesthesia of the skin 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 of the formulation of the topical drug delivered using this method.

Objective: The primary objective of this study is to assess the analgesic effect of fractional carbon dioxide laser assisted delivery of two topical anesthetics (articaine hydrochloride 40 mg/ml and epinephrine 10 μg/ml solution (AHES) and EMLA cream) compared to application of these anesthetics without fractional laser pretreatment. The secondary objective is to compare the efficacy of these two different anesthetics, when applied according to the fractional laser drug delivery principle.

Study design: Prospective, single blinded, randomized, controlled, within subject, pilot study.

Study population: 10 healthy volunteers ≥18 years, who give written informed consent Intervention: In each subject, four test regions on subject's back of 1x1 centimeter will be randomly allocated in a 2x2 design to (1) ablative fractional laser (AFXL) pretreatment (5% density, 2.5 mJ/microbeam) followed by topical application of AHES, (2) AFXL pretreatment followed by application of EMLA cream, (3) sham AFXL followed by application of AHES on the intact skin and (4) sham AFXL followed by application of EMLA cream on the intact skin. Sham AFXL will be done by delivering an AFXL pass at 5% density and 2.5 mJ/microbeam right adjacent to the region of AHES or EMLA application on the intact skin. After ten minutes incubation time, an AFXL pass will be given as a pain stimulus at each test region with 5% density and 35 mJ/microbeam. 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 each pain stimulus.

Inclusion Criteria:

• Fitzpatrick skin type I or II
• Age ≥18 years
• Patient is willing and able to give written informed consent

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
• Fitzpatrick skin type III-VI
• Excessive sun tan