Skin penetration of silica microparticles.

Knowledge about skin penetration of nano- and microparticles is essential for the development of particle-core drug delivery systems and toxicology. A large number of studies have been devoted to metallic particle penetration. However, little work has been published about the importance of chemical material properties of the particles and the skin penetration effect of the applied formulation. Here, we investigated the penetration of 3 microm silica particles in water and in a 65% ethanolic plant extract on ex vivo human skin using scanning electron microscopy. Contrary to most other microsphere skin studies, we observed for the first time that 3 microm silica particles can penetrate the living epidermis. Moreover, when formulated in the ethanolic medium, particles even reach the dermis. The deviating chemical properties of silica compared to previously investigated microparticles (titanium dioxide, zinc oxide) and confounding effect of the formulation in which the silica microparticles are presented, is thus demonstrated.

Ion mobility spectrometry as a high-throughput technique for in vitro transdermal Franz diffusion cell experiments of ibuprofen.

Rapid, low-cost and sensitive analytical methods are needed to analyse the large number of samples that are generated when investigating the absorption profile of drugs through the skin using Franz diffusion cell experiments (FDC). The goal of this study was to evaluate the potential of ion mobility spectrometry (IMS) for the quantitative analysis of active pharmaceutical ingredients (API) in transdermal research. Ibuprofen was used as a model drug and the optimal IMS parameters were determined using a Doehlert experimental design. To assess the usefulness of the IMS method, FDC experiments using human skin were conducted, covering a concentration range of 0.32-69.57µg/ml. The resulting analytical samples were analysed using IMS and subsequently compared to HPLC as a reference method. No significant differences were found between the results obtained using both analytical methods, with a mean skin permeability coefficient (K(p)) value of 0.013cm/h. The combination of fast detection times, sensitivity, low costs and easy maintenance of IMS instruments makes this technique an attractive alternative for HPLC in this type of experiments.

Local skin pharmacokinetics of talarozole, a new retinoic acid metabolism-blocking agent.

Talarozole is a new highly potent and selective azole derivative which inhibits cytochrome-P450-dependent all-trans-retinoic acid catabolism. It is in clinical development for the treatment of psoriasis and acne. However, no local pharmacokinetic data on the diffusion behaviour of talarozole in the skin itself are available. As topical application might be an interesting alternative to oral therapy because of the reduced systemic side effects, the aim of this study was to assess the transdermal behaviour of topically applied talarozole, including its within-skin distribution. Franz diffusion cell experiments with talarozole dissolved in different pharmaceutically relevant solvents (i.e. propylene glycol, oleolyl macrogol glyceride, isopropyl myristate, diethylene glycol monoethylether, ethanol, caprylic/capric triglyceride and caprylocaproyl macrogol glyceride) were performed to assess the transdermal behaviour of talarozole. Talarozole slightly diffused into the skin only when dissolved in propylene glycol, isopropyl myristate or ethanol. Although only 0.1% of the dose applied was found in the skin itself after 12-24 h, this was sufficient to achieve local concentrations well above the half-maximal inhibitory concentration value for talarozole. The distribution of talarozole within the skin was investigated: 80% was located in the epidermis, while the remaining 20% was found in the dermis. The epidermal concentration of talarozole achieved after a single topical application was sufficiently high to enable the potential induction of local retinoid-like effects.

Quality analytics of Internet pharmaceuticals.

Trading pharmaceutical products through the Internet poses several challenges related to legal responsibilities, good distribution practices, information content and patient use, financial implications, but also regarding product quality. One of the major concerns is the well-known phenomenon of counterfeited and/or substandard drugs commercialized through rogue Internet sites. Therefore, controlling and assuring the quality of those products has become an important and challenging task for the authorities. This review gives an overview of the different quality attributes that can be evaluated to have a complete understanding of the quality of the finished pharmaceutical product traded through the Internet, as well as the current analytical techniques that serve this objective. Aspects considered are labelling and packaging, physicochemical quality attributes, identification and assay of active substances and/or excipients, impurity profiling, biopharmaceutical testing and data interpretation.

LC-MS profiling of N-alkylamides in Spilanthes acmella extract and the transmucosal behaviour of its main bio-active spilanthol.

N-Alkylamides are a promising group of naturally occurring bio-actives, with evidence for immune stimulating properties, which find applications i.a. in buccal preparations. In Spilanthes extracts, these properties are mainly ascribed to the most abundant N-isobutylamide, spilanthol. Yet, other N-alkylamides present in these extracts may contribute to this effect, as well as to its potential toxicity and physiologic interactions. Therefore, N-alkylamide profiling of an ethanolic Spilanthes extract was performed using a gradient reversed phase high performance liquid chromatography/electrospray ionization ion trap mass spectrometry (HPLC/ESI-MS) method on an embedded polar column. MS(1) and MS(2) fragmentation data were used for identification purposes. Moreover, the transmucosal behaviour of spilanthol, formulated in this ethanolic extract and in two commercially available oral gels, was evaluated using porcine buccal mucosa in a Franz diffusion cell experimental set-up. A high-throughput HPLC-UV method was used for the quantification of spilanthol in the receptor phase. Fundamental permeation characteristics of spilanthol in a solvent-independent way (100% aqueous dose solution) were obtained using different propylene glycol/water ratios. Eight N-isobutylamides, two 2-methylbutylamides and one 2-phenylethylamide were detected, with spilanthol as most abundant N-alkylamide (88.8%). Up till now, two of these N-isobutylamides were not yet described in Spilanthes extracts. We demonstrated for the first time that spilanthol permeates the buccal mucosa. Depending on the formulation, a more pronounced local or systemic effect is achieved, which is important for the regulatory product classification. The purely aqueous permeation coefficient K(p,aq) (+/-SEM) was found to be 11.3 (+/-0.403)10(-3)cm/h.

Transdermal behaviour of the N-alkylamide spilanthol (affinin) from Spilanthes acmella (Compositae) extracts.

AIM OF THE STUDY: N-Alkylamides are a large group of bioactive molecules found in several plants from the genera Echinacea, Xanthoxylum and Spilanthes. Extracts and formulations derived from these plants are not only orally used, but also applied on the skin as well. However, there is currently no specific information available about the intrinsic local pharmacokinetics of N-alkylamides after topical application on human skin, questioning the role of this mode of administration. The present study investigates the transdermal behaviour of spilanthol, a prominent N-alkylamide. MATERIALS AND METHODS: Two pharmaceutically accepted dose solutions (ethanol and propylene glycol based aqueous donor vehicles), combined with three different receptor fluids (PBS, PBS+0.5% HPbetaCD, EtOH/H(2)O (30:70, v/v)), were applied on split-thickness human skin in a Franz diffusion cell (FDC) system. Fundamental permeation characteristics of spilanthol in a solvent-independent way (100% aqueous dose solution) were also obtained using an extrapolation approach with different organic solvent/H(2)O ratios. RESULTS AND CONCLUSIONS: We demonstrated for the first time that spilanthol permeates the skin. The following aqueous-extrapolated primary transdermal parameters were obtained (mean+/-SEM): K(p,aq)=3.31 (+/-0.29)x10(-3)cm/h, D(m,aq)=1.86 (+/-0.09)x10(-4)cm(2)/h and K(m,aq)=7.28 (+/-1.59)x10(-1). Partitioning (K(m)) was strongly dependent on the donor solution composition, while diffusion (D(m)) was mainly influenced by the receptor fluid composition.

Analytical, biopharmaceutical and regulatory evaluation of topical testosterone preparations.

Testosterone-containing pharmaceutical products for topical use were obtained from the pharmacist or through the internet. The legal status of the different products obtained is discussed: some products through the internet were clearly a medicinal product according to the current definitions, while they are not registered as such. Assay and impurity profiles of each of the marketed samples were obtained using HPLC-UV and ESI-iontrap MS. The analytical results were evaluated relative to the reporting, identification and qualification thresholds as defined by the the International Conference on Harmonisation (ICH) and the European Pharmacopoeia (Ph. Eur.). Preparations with impurities above the qualification threshold were observed. Moreover, in vitro release profiles over an artificial membrane were obtained using a standardised cell in a paddle dissolution bath as well as in a static Franz diffusion cell, using phosphate buffered saline (PBS; pH 7.0) containing 5% bovine serum albumin (BSA) as dissolution or receptor fluid. This biopharmaceutical quality attribute differs significantly between the preparations tested. In conclusion, the equivalency of topical testosterone preparations is not assured, nor on their legal status, nor on their impurity profiling nor on their biopharmaceutical behaviour. This calls for an urgent trans-national product-class harmonisation approach.

Stability of the OECD model compound benzoic acid in receptor fluids of Franz diffusion cells.

The stability of benzoic acid, one of the model compounds recommended for skin absorption studies in the OECD guidelines, in Franz diffusion cell receptor fluids was studied. According to the results, addition of a preservative (sodium azide) to the solution is recommended for long-term skin permeation experiments.

Assessment of the solid-state composition of an active salicylanilide compound by FT-Raman spectroscopy.

A biologically active salicylanilide compound currently appears in three known solid-state forms: polymorph I (Pol I), polymorph II (Pol II) and the amorphous form (Amorph). The obtained FT-Raman spectra revealed several regions of interest (ROIs) qualitatively distinguishing the different forms, allowing samples with an unknown polymorphic composition to be quantitatively analysed by FT-Raman spectroscopy. The Markov-transformed peak areas of the Raman-bands in the ROIs from the samples were determined and compared with the transformed peak areas obtained for the reference solid-state forms. A constrainted linear regression model estimated the contribution of each reference to the different samples. The applicability of this approach was demonstrated by analysing commercially available batches.

Analysis of iodinated peptides by LC-DAD/ESI ion trap mass spectrometry.

The analysis of iodinated peptides resulting from chloramine-T (CAT), Iodo-Beads, Iodo-Gen and lactoperoxidase iodination reactions in the preparation of nanomole quantities 125I and 123I labelled tracers is described. Seven different model peptides were evaluated, varying in molecular weight from 294 (LY-dipeptide) to 2518 (obestatin containing 23 amino acid residues). Two different RP-C18 columns were used, each with a different gradient system based on aqueous formic acid and acetonitrile. Electrospray ionization (ESI) ion trap mass spectrometry was used for identification of the chromatographic eluting components of the reaction mixtures, while UV (DAD) served quantitative purposes. Non-, mono-, di-, tri- and tetra-iodinated peptides (respectively NIP, MIP, DIP, 3IP and 4IP) eluted in that order and were well separated from each other. An empirical model was derived. The applicability of this approach was demonstrated by the analysis of different reaction mixtures.