The role of formulation and follicular pathway in voriconazole cutaneous delivery from liposomes and nanostructured lipid carriers.

In general, colloids provide increased cutaneous permeation of drugs. Still, skin interaction and main pathways for drug diffusion may vary depending on system and formulation characteristics. The knowledge of how different colloidal systems interact with biological membranes and the formulation impact on delivery is especially relevant for drugs that can be encapsulated in multiple nanosystems, as voriconazole (VOR). In here, we compared VOR release and permeation profile from liposomes (LP) and nanostructured lipid carriers (NLC) in aqueous colloidal dispersions and in gel formulations. Despite the controlled drug release provided by gel formulations, formulation only had a significant impact on drug skin accumulation from LP. The reduced mobility in gel formulations compromised follicle deposition and drug retention in the skin. Such a hypothesis was confirmed by permeation experiments evaluating follicle pathway influence. Follicular route also had an influence on delivery from NLC, which was only significant for total drug that reached the acceptor medium. These differences could be attributed to the mechanisms of colloid interaction with the skin and subsequent drug release. Follicle LP deposition and slow drug release leads to higher cutaneous amounts whilst NLC interaction with skin and fast drug release leads to fast drug diffusion and deeper penetration. By the low MIC50 values encountered against Trichophyton rubrum (∼ 0.001 µg/mL), permeated amounts could inhibit fungal growth, regardless the system. In conclusion, both LP and NLC seem to be valuable systems for cutaneous VOR delivery. Fluidic formulations could provide better efficiency for cutaneous drug delivery from LP.

Minoxidil topical treatment may be more efficient if applied on damp scalp in comparison with dry scalp.

There is yet no consensus among prescribers whether minoxidil (MXD) formulations should be applied on wet/damp or dry scalp and no clear FDA guidelines on the matter. We hypothesized that the use of MXD on damp scalp may lead to higher drug penetration. First, because the drug diffusion and consequent deposition into the hair follicle may be favored when follicle cast is humid. Second, because humidity may also prevent drug crystallization and, therefore, maintain a higher thermodynamic activity for longer periods, which leads to increased penetration. Following in vitro experiments on rat and porcine skin we confirmed the hypothesis, which could markedly improve treatment effectiveness.

Excised porcine cornea integrity evaluation in an in vitro model of iontophoretic ocular research.

BACKGROUND/AIMS: It is a challenge to adapt traditional in vitro diffusion experiments to ocular tissue. Thus, the aim of this work was to present experimental evidence on the integrity of the porcine cornea, barrier function and maintenance of electrical properties for 6 h of experiment when the tissue is mounted on an inexpensive and easy-to-use in vitro model for ocular iontophoresis. METHODS: A modified Franz diffusion cell containing two ports for the insertion of the electrodes and a receiving compartment that does not need gassing with carbogen was used in the studies. Corneal electron transmission microscopy images were obtained, and diffusion experiments with fluorescent markers were performed to examine the integrity of the barrier function. The preservation of the negatively charged corneal epithelium was verified by the determination of the electro-osmotic flow of a hydrophilic and non-ionized molecule. RESULTS: The diffusion cell was able to maintain the temperature, homogenization, porcine epithelial corneal structure integrity, barrier function and electrical characteristics throughout the 6 h of permeation experiment, without requiring CO(2) gassing when the receiving chamber was filled with 25 mM of HEPES buffer solution. CONCLUSION: The system described here is inexpensive, easy to handle and reliable as an in vitro model for iontophoretic ocular delivery studies.