In Vitro Permeation Test (IVPT) for Pharmacokinetic Assessment of Topical Dermatological Formulations.

In vitro assessment of topical (dermal) pharmacokinetics is a critical aspect of the drug development process for semi-solid products (e.g., solutions, foams, sprays, creams, gels, lotions, ointments), allowing for informed selection of new chemical entities, optimization of prototype formulations during the nonclinical stage, and determination of bioequivalence of generics. It can also serve as a tool to further understand the impact of different excipients on drug delivery, product quality, and formulation microstructure when used in parallel with other techniques, such as analyses of rheology, viscosity, microscopic characteristics, release rate, particle size, and oil droplet size distribution. The in vitro permeation test (IVPT), also known as in vitro skin penetration/permeation test, typically uses ex vivo human skin in conjunction with diffusion cells, such as Franz (or vertical) or Bronaugh (or flow-through) diffusion cells, and is the technique of choice for dermal pharmacokinetics assessment. Successful execution of the IVPT also involves the development and use of fit-for-purpose bioanalytical methods and procedures. The protocols described herein provide detailed steps for execution of the IVPT utilizing flow-through diffusion cells and for key aspects of the development of a liquid chromatography-tandem mass spectrometry method intended for analysis of the generated samples (epidermis, dermis, and receptor solution). © 2020 Wiley Periodicals LLC. Basic Protocol 1: In vitro permeation test Support Protocol: Dermatoming of ex vivo human skin Basic Protocol 2: Bioanalytical methodology in the context of the in vitro permeation test.

Stress and Drug Dependence Differentially Modulate Norepinephrine Signaling in Animals with Varied HPA Axis Function.

Previous work has demonstrated the importance of genetic factors and stress-sensitive circuits in the development of affective disorders. Anxiety and numerous psychological disorders are comorbid with substance abuse, and noradrenergic signaling in the bed nucleus of the stria terminalis (BNST) is thought to be a source of this convergence. Here, we examined the effects of different stressors on behavior and norepinephrine dynamics in the BNST of rat strains known to differ in their HPA-axis function. We compared the effects of acute morphine dependence and social isolation in non-anxious Sprague Dawley (SD) rats, and a depression model, Wistar-Kyoto (WKY) rats. We found a shared phenotype in drug-dependent and singly housed SD rats, characterized by slowed norepinephrine clearance, decreased autoreceptor function, and elevated anxiety. WKY rats exhibited changes in anxiety and autoreceptor function only following morphine dependence. To ascertain the influence of LC inhibition on this plasticity, we administered the LC-terminal-selective toxin DSP-4 to SD and WKY rats. DSP-4-treated SD rats demonstrated a dependence-like phenotype, whereas WKY rats were unchanged. Overall, our findings suggest that individuals with varying stress susceptibilities have different noradrenergic signaling changes in response to stress. These changes may establish conditions that favor stress-induced reinstatement and increase the risk for addiction.