Objectives: Needle-free jet injectors have been used in dermatological practice for many years. However, predefined clinical endpoints that guide physicians to choose optimal device settings have not been clearly defined. Here, we evaluate immediate skin responses as clinical endpoints for needle-free jet injector treatments. Methods: We injected methylene blue in ex vivo human skin using an electronically-controllable pneumatic injector (EPI; 3-6 bar, 50-130 µl; n = 63), and a spring-loaded jet injector (SLI) with fixed settings (100 µl; n = 9). We measured the immediate skin papule (3D-camera), residual surface fluid (pipette), dermal dye distribution by estimating depth and width, and subcutaneous dye deposition. Results: EPI with 4 bar and 100 µl resulted in the largest skin papule of 48.7 mm 3 (35.4-62.6 mm 3 ) and widest dermal distribution of 8.0 mm (5.5-9.0 mm) compared to EPI with 6 bar and 100 µl (p < 0.001, p = 0.018, respectively). The skin papule volume showed a significant moderate to high positive correlation with the width and depth of dye distribution in the dermis (r s = 0.63, r s = 0.58, respectively; p < 0.001 for both correlations). SLI showed high variability for all outcome measures. Finally, a trend was observed that a small skin papule (≤7 mm) and little residual surface fluid (≤10% of injection volume) were warning signs for subcutaneous deposition. Conclusions: The immediate skin papule and residual surface fluid correspond with dermal drug deposition and are relevant clinical endpoints for needle-free jet injector treatments in dermatological practice.

<b><i>Background:</i></b> Nonattendance is common among patients suffering from delusional infestation (DI) with a risk factor for poorer patient outcomes. <b><i>Objective:</i></b> The aim of this study was to determine the incidence rate and predictors of nonattendance among patients presenting to a psychodermatology department with DI and the subsequent effect on the success of prescribing new antipsychotics. <b><i>Methods:</i></b> Data of 265 patients were reviewed of the Amsterdam UMC, the Erasmus University Medical Center, the Royal London Hospital, and the Liverpool School of Tropical Medicine between January 2008 and October 2019. <b><i>Results:</i></b> We observed that among the patients who attended the first consultation, 57% (<i>n</i> = 144) did not attend their second visit. Recreational drug use was significantly higher in the nonattendance group compared to the attendance group (25% against 18%). Patients who had a history of previously prescribed antipsychotics at the time of the first consultation were less likely to get prescribed antipsychotics from the psychodermatology departments for DI; however, prescribing antipsychotic drugs by the psychodermatology department did not influence nonattendance significantly. <b><i>Conclusions:</i></b> People suffering from DI are at high risk of nonattendance, even in specialist settings. Patients with current illicit drug use and younger patients are particularly at risk of this.