Comparison of the thermogravimetric analysis (TGA) and Franz cell methods to assess dermal diffusion of volatile chemicals

Effect of Complexes and Microemulsions on the Permeability of Drugs: Determination Using a New Biomimetic Artificial Membrane

The aim of this work was to predict the permeability of two model drugs, sulfamerazine (SMR) and indomethacin (INM), and to determine the effect on their apparent permeabilities by complexation with cyclodextrins and/or meglumine or incorporation in microemulsions. Permeation experiments were performed using two-chamber diffusion cells with a new composition of bio-mimetic membrane composed of 80% of Lipoid® S100 and 20% of cholesterol in n-octanol 10% w/w solution, at 37 ± 0.5°C and 14,000 rpm. The predictive capacity of the permeability of passive diffusion absorbed compounds was evaluated using 20 drug standards and showed an exponential correlation between the apparent permeability coefficients (P_app) and the fraction absorbed percentages in humans (Fa%), with an R² value of 0.67942 and a constant value of - 4.1 ± 0.8. SMR and INM were classified as Class II and I, respectively, according to the Biopharmaceutical Classification System. These drugs were complexed and incorporated in microemulsions. The Fa% from all the drug products was higher than 90%. SMR in the complexes and both drugs in microemulsions were classified as highly soluble. Thus, SMR and INM incorporated in these pharmaceutical products could be classified as Class I.

Gross and histological description of the epidermal membrane found on normal neonatal piglets

The structure and composition of fetal and placental tissues vary among different species of placental mammals. Some mammals, including camelids and pigs, possess an epidermal membrane during the fetal stage, called the epithelion, that is absent from other domestic mammals. Because neonatal piglets are a common animal model for many research techniques, it is important that researchers correctly identify this tissue and recognize its lack of pathological consequence when working with fetal and neonatal piglets. Here, the authors describe gross and histological examinations of the epithelion, comparing this tissue with other extra-fetal tissues and coatings.

Permeation measurement of gestodene for some biodegradable materials using Franz diffusion cells

Biodegradable poly(d,l-lactide) (PDLLA), Poly(trimethylene carbonate) (PTMC), polycaprolactone (PCL), poly(caprolactone-co-d,l-lactide) (PCDLLA) and poly(trimethylene carbonate-co-caprolactone) (PTCL) are recently used for clinical drug delivery system such as subcutaneous contraceptive implant capsule due to their biodegradable properties that they could possess long-term stable performance in vivo without removal, however their permeation rate is unknown. In the work, biodegradable material membranes were prepared by solvent evaporation using chloroform, and commercial silicone rubber membrane served as a control. Gestodene was used as a model drug. Gestodene has high biologic progestational activity which allows for high contraceptive reliability at very low-dose levels. The permeation rate of gestodene for several biodegradable materials was evaluated. In vitro diffusion studies were done using Franz diffusion cells with a diffusion area of 1.33 cm². Phosphate buffer solution (PBS, pH 7.4), 10% methanol solution and distilled water were taken in donor and receiver chambers at temperature of 37 °C respectively. The in vitro experiments were conducted over a period of 24 h during which samples were collected at regular intervals. The withdrawn samples were appropriately diluted and measured on UV–vis spectrophotometer at 247 nm. Conclusion data from our study showed that permeation rate of PCDLLA with CL ratio more than 70% could be more excellent than commercial silicone rubber membrane. They may be suitable as a candidate carrier for gestodene subcutaneous contraceptive implants in contraceptive fields.

Predicting the absorption of chemical vapours

The focus of this review is on the systemic absorption of vapours via skin, including experimental data as well as regression and pharmacokinetic models. Dermal contribution ratios (DCR), i.e. amount absorbed through skin relative to total intake (skin and inhalation) at specified conditions, could be identified or calculated from published data for 33 chemical vapours. The ratios vary from ~0.0002 (vinyl chloride) to ~0.8 (2-butoxyethanol), with hydrophilic chemicals having a higher ratio than lipophilic ones. Multiple regression analysis of these data suggests that the DCR is largely explained by the octanol:water partition coefficient, vapour pressure and molecular weight (R(2)=0.69). Several physiologically-based pharmacokinetic models were identified; however, all describe the absorption of single substances. Regarding predictive models, only two models were found. In conclusion, dermal uptake of chemical vapours needs more attention, as such exposures are common, data are scarce and few predictive models exist.

The relevance of polymeric synthetic membranes in topical formulation assessment and drug diffusion study

Synthetic membranes are composed of thin sheets of polymeric macromolecules that can control the passage of components through them. Generally, synthetic membranes used in drug diffusion studies have one of two functions: skin simulation or quality control. Synthetic membranes for skin simulation, such as the silicone-based membranes polydimethylsiloxane and Carbosil, are generally hydrophobic and rate limiting, imitating the stratum corneum. In contrast, synthetic membranes for quality control, such as cellulose esters and polysulfone, are required to act as a support rather than a barrier. These synthetic membranes also often contain pores; hence, they are called porous membranes. The significance of Franz diffusion studies and synthetic membranes in quality control studies involves an understanding of the fundamentals of synthetic membranes. This article provides a general overview of synthetic membranes, including a brief background of the history and the common applications of synthetic membranes. This review then explores the types of synthetic membranes, the transport mechanisms across them, and their relevance in choosing a synthetic membrane in Franz diffusion cell studies for formulation assessment purposes.