Not enough patients eligible for recruitment.

The purpose of this study is to assess the efficacy of skin anesthesia using fractional laser assisted delivery of articaine hydrochloride 40 mg/ml and epinephrine 10 µg/ml solution (AHES) compared to standard anesthesia with topical eutectic mixture of lidocaine 25 mg/g and prilocaine 25 mg/g cream (EMLA cream) prior to ablative fractional laser treatment of acne scars and traumatic scars.

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, Haedersdal and colleagues have shown that the penetration of various topically applied substances, including photosensitizers, into the skin can be enhanced and accelerated by pretreatment of the skin with a fractional laser, creating a pattern of microscopic ablation craters.1 This improvement in drug penetration is regardless of ablation crater depth.2 There is limited evidence that transepidermal lidocaine absorption can be increased by fractional laser pretreatment.3, 4 These findings might suggest that local anesthesia of the skin may be achieved by applying an anesthetic topically on a skin surface pretreated with a fractional laser. The investigators of the present study hypothesize that fractional laser assisted delivery of topical anesthetics might give a faster and better anesthetic effect, than treatment with the standard treatment of topical anesthesia.

Objective: The objective of this study is to assess the efficacy of skin anesthesia using fractional laser assisted delivery of articaine hydrochloride 40 mg/ml and epinephrine 10 µg/ml solution (AHES) compared to standard anesthesia with topical eutectic mixture of lidocaine 25 mg/g and prilocaine 25 mg/g cream (EMLA cream).

Study design: Prospective, open label, randomized controlled, within subject, study.

Study population: patients >18 years, who give written informed consent, visiting the institute for fractional carbon dioxide laser treatment for acne scars or traumatic scars.

Intervention (if applicable): In each patient, the lesional area will be divided into two comparable regions during the visit prior to the (next) fractional laser treatment. These regions will then be randomly allocated to either standard anesthesia with EMLA cream (control region; region I) or ablative fractional laser (AFXL) assisted delivery of AHES (intervention region; region II). Patients will be asked to apply EMLA cream at region I under occlusion two hours prior to the laser treatment. Fifteen minutes before the therapeutic laser treatment of the scars, the skin of region II will be pretreated with the fractional carbon dioxide laser (15% density, 2.5 mJ/microbeam). Directly following fractional laser pretreatment, AHES will be topically applied under occlusion at region II for 15 minutes. Subsequently treatment of both regions will be performed with the same fractional carbon dioxide laser at the settings used in routine clinical practice. Directly after this therapeutic laser treatment, patients will be asked to indicate pain per test region on a visual analogue scale (VAS) from 0-10 (0: no pain; 10: worst imaginable pain).

Inclusion Criteria:

• Patients with acne scars or traumatic scars scheduled for treatment with the fractional carbon dioxide laser
• Age ≥18 years
• Patient is willing and able to give written informed consent

Exclusion Criteria:

• 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
• Total lesional area to be treated in one session >600 cm2