In vitro percutaneous absorption of piroxicam through synthetic membranes and abdominal rat skin

Dissipative Particle Dynamics Investigation of the Transport of Salicylic Acid through a Simulated In Vitro Skin Permeation Model

Permeation models are often used to determine diffusion properties of a drug through a membrane as it is released from a delivery system. In order to circumvent problematic in vivo studies, diffusion studies can be performed in vitro, using (semi-)synthetic membranes. In this study salicylic acid permeation was studied, employing a nitrocellulose membrane. Both saturated and unsaturated salicylic acid solutions were studied. Additionally, the transport of salicylic acid through the nitrocellulose membrane was simulated by computational modelling. Experimental observations could be explained by the transport mechanism that was revealed by dissipative particle dynamics (DPD) simulations. The DPD model was developed with the aid of atomistic scale molecular dynamics (AA-MD). The choice of a suitable model membrane can therefore, be predicted by AA-MD and DPD simulations. Additionally, the difference in the magnitude of release from saturated and unsaturated salicylic acid and solutions could also be observed with DPD. Moreover, computational studies can reveal hidden variables such as membrane-permeant interaction that cannot be measured experimentally. A recommendation is made for the development of future model permeation membranes is to incorporate computational modelling to aid the choice of model.

Pluronic lecithin organogel of 5-aminosalicylic acid for wound healing

5-Aminosalicylic acid (5-ASA) is an aminosalicylate anti-inflammatory drug, which is also known as mesalazine or mesalamine. Currently employed in treating inflammatory bowel disease, ulcerative colitis, inflamed anus or rectum, and maintain remission in Crohn's disease. Evidence from the researchers highlighted its significant re-epithelization in allergic asthma, aphthous, and gastric ulcerative conditions. The objective of the study was to formulate the pluronic lecithin organogel (PLO) containing 5-ASA and evaluate its wound-healing ability in a full thickness excision wound rat model. The data obtained from in silico docking studies revealed 5-ASA is having an affinity towards the transforming growth factor-beta (TGF-β) specifically towards beta1. Among various formulations prepared (F1 to F8), F1, and F6 have shown a maximum in vitro drug release with optimum pH and viscosity. From MTT assay it was found that selected PLO formulations showed no toxicity and enhanced cell proliferation in HaCaT cell lines. In vivo wound-healing studies in albino Wistar rats has revealed that PLO accelerates wound closure and reepithelization to the statistically significant level on day 3 (p < .05) in comparison with untreated wounds. In conclusion, the overall results suggest that 5-ASA PLO gel is a potential therapeutic option for the treatments of wounds, however, further studies are highly warrened to determine the various mechanisms of 5-ASA in regulating the cell migration and reepithelization in wound healing to outspread its use in clinics.

Comparative evaluation of rivastigmine permeation from a transdermal system in the Franz cell using synthetic membranes and pig ear skin with in vivo-in vitro correlation

In the present study, in vitro permeation experiments in a Franz diffusion cell were performed using different synthetic polymeric membranes and pig ear skin to evaluate a rivastigmine (RV) transdermal drug delivery system. In vitro-in vivo correlations (IVIVC) were examined to determine the best model membrane. In vitro permeation studies across different synthetic membranes and skin were performed for the Exelon(®) Patch (which contains RV), and the results were compared. Deconvolution of bioavailability data using the Wagner-Nelson method enabled the fraction of RV absorbed to be determined and a point-to-point IVIVC to be established. The synthetic membrane, Strat-M™, showed a RV permeation profile similar to that obtained with pig ear skin (R(2)=0.920). Studies with Strat-M™ resulted in a good and linear IVIVC (R(2)=0.991) when compared with other synthetic membranes that showed R(2) values less than 0.90. The R(2) for pig ear skin was 0.982. Strat-M™ membrane was the only synthetic membrane that adequately simulated skin barrier performance and therefore it can be considered to be a suitable alternative to human or animal skin in evaluating transdermal drug transport, potentially reducing the number of studies requiring human or animal samples.

Propolis organogel as a novel topical delivery system for treating wounds

CONTEXT

Propolis has traditionally been used in curing infections and healing wounds and burns.

OBJECTIVE

The aim of this study is to formulate pluronic lecithin organogel of propolis to improve its availability and antimicrobial activity.

MATERIALS AND METHODS

Different organogels were prepared by using soybean lecithin, isopropyl palmitate, pluronic F127 and water. The effect of quantity of lecithin and pluronic F127 and percentage of oil phase was investigated. The organogels were evaluated for appearance, texture, pH, drug content and viscosity. In vitro release studies were carried out using cellophane membrane. Drug permeation through abdominal rat skin from organogels that showed high % drug release was compared to that from propolis suspension in distilled water. Finally, the antimicrobial activity of the selected propolis formulation against different bacterial isolates was compared with that of propolis suspension in water.

RESULTS AND DISCUSSION

Results showed that all organogel formulations except the formula containing 10% pluronic F127, showed acceptable physical properties. Drug content of organogel formulations was in the range of 97.5-100.2%. The pH of the formulations was in the range of 5.5-6.3 that suits the skin pH, indicating skin compatibility. The viscosity was in the range of 5366-8984 cp. A significant decrease in drug release from formulations was observed with increase in concentration of lecithin and pluronic F127. Decreasing oil phase percentage to 20% w/w led to a decrease in drug release from the formulation.

CONCLUSION

The formula containing 3% lecithin and 20% pluronic F127 exhibited superior skin permeation and antimicrobial activity over propolis suspension in water.

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.

In vitro permeation and in vivo anti-inflammatory and analgesic properties of nanoscaled emulsions containing ibuprofen for topical delivery

INTRODUCTION

As a topical delivery system, a nanoscaled emulsion is considered a good carrier of several active ingredients that convey several side effects upon oral administration, such as nonsteroidal anti-inflammatory drugs (NSAIDs).

OBJECTIVE

We investigated the in vitro permeation properties and the in vivo pharmacodynamic activities of different nanoscaled emulsions containing ibuprofen, an NSAID, as an active ingredient and newly synthesized palm olein esters (POEs) as the oil phase.

METHODOLOGY

A ratio of 25:37:38 of oil phase:aqueous phase:surfactant was used, and different additives were used for the production of a range of nanoscaled emulsions. Carbopol® 940 dispersion neutralized by triethanolamine was employed as a rheology modifier. In some circumstances, menthol and limonene were employed at different concentrations as permeation promoters. All formulae were assessed in vitro using Franz diffusion cell fitted with full-thickness rat skin. This was followed by in vivo evaluation of the anti-inflammatory and analgesic activities of the promising formulae and comparison of the effects with that of the commercially available gel.

RESULTS AND DISCUSSION

Among all other formulae, formula G40 (Carbopol® 940-free formula) had a superior ability in transferring ibuprofen topically compared with the reference. Carbopol® 940 significantly decreased the amount of drug transferred from formula G41 through the skin as a result of swelling, gel formation, and reduction in drug thermodynamic activity. Nonetheless, the addition of 10% w/w of menthol and limonene successfully overcame this drawback since, relative to the reference, higher amount of ibuprofen was transferred through the skin. By contrast, these results were relatively comparable to that of formula G40. Pharmacodynamically, the G40, G45, and G47 formulae exhibited the highest anti-inflammatory and analgesic effects compared with other formulae.

CONCLUSION

The ingredients and the physical properties of the nanoscaled emulsions produced by using the newly synthesized POEs succeeded to deliver ibuprofen competently.

Topical piroxicam in vitro release and in vivo anti-inflammatory and analgesic effects from palm oil esters-based nanocream

INTRODUCTION

During recent years, there has been growing interest in use of topical vehicle systems to assist in drug permeation through the skin. Drugs of interest are usually those that are problematic when given orally, such as piroxicam, a highly effective anti-inflammatory, anti-pyretic, and analgesic, but with the adverse effect of causing gastrointestinal ulcers. The present study investigated the in vitro and in vivo pharmacodynamic activity of a newly synthesized palm oil esters (POEs)-based nanocream containing piroxicam for topical delivery.

METHODS

A ratio of 25:37:38 of POEs: external phase: surfactants (Tween 80:Span 20, in a ratio 80:20), respectively was selected as the basic composition for the production of a nanocream with ideal properties. Various nanocreams were prepared using phosphate-buffered saline as the external phase at three different pH values. The abilities of these formulae to deliver piroxicam were assessed in vitro using a Franz diffusion cell fitted with a cellulose acetate membrane and full thickness rat skin. These formulae were also evaluated in vivo by comparing their anti-inflammatory and analgesic activities with those of the currently marketed gel.

RESULTS

After eight hours, nearly 100% of drug was transferred through the artificial membrane from the prepared formula F3 (phosphate-buffered saline at pH 7.4 as the external phase) and the marketed gel. The steady-state flux through rat skin of all formulae tested was higher than that of the marketed gel. Pharmacodynamically, nanocream formula F3 exhibited the highest anti- inflammatory and analgesic effects as compared with the other formulae.

CONCLUSION

The nanocream containing the newly synthesized POEs was successful for trans-dermal delivery of piroxicam.

A Comparative Study of Transmembrane Diffusion and Permeation of Ibuprofen across Synthetic Membranes Using Franz Diffusion Cells

Synthetic membranes used in Franz diffusion cells for topical formulation quality assessment should provide least resistance to drug diffusion. In this study, the diffusion rates of ibuprofen across thirteen membranes were determined using Franz diffusion cells. Correlation of the membrane thickness, pore size and MWCO with drug fluxes was also made. The drug diffusion results showed that the porous membranes were categorized into high-flux (8-18 mg/cm²/h) and low-flux (0.1-3 mg/cm²/h) membranes. The drug fluxes did not show strong correlations (r² < 0.99) with membrane parameters. Synthetic membranes can give variable drug fluxes, thus investigators should be careful in choosing membrane for formulation quality assessment.

In vitro skin absorption and drug release – A comparison of six commercial prednicarbate preparations for topical use

Reconstructed human epidermis is a useful tool for in vitro skin absorption studies of chemical compounds. If this may hold true also for topical dermatics, we investigated the glucocorticoid prednicarbate applied by two sets (innovator and generic) of cream, ointment and fatty ointment using the commercially available EpiDerm model. Moreover, stability and local tolerability of the preparations as well as drug release were studied, to estimate an influence on prednicarbate absorption and metabolism. While release ranked in the order cream<fatty ointment<ointment for both sets of preparations, prednicarbate penetration and permeation of the EpiDerm model did not. Less PC uptake observed with the generic ointment and fatty ointment appeared to be linked to impaired enzymatic ester cleavage within the tissue. Thus with drugs subject to skin metabolism, cutaneous uptake is not to be derived from drug release studies, yet has to be studied experimentally with viable skin or reconstructed human epidermis.

In vitro percutaneous penetration of acyclovir from solvent systems and Carbopol 971-P hydrogels: influence of propylene glycol

The mechanism underlying propylene glycol (PG) effects on acyclovir (ACV) penetration through human epidermis were studied. Solvent systems and Carbopol gels containing increasing percentage of PG (from 0% to 70%, w/w) were used. Viscosity studies of both vehicles were carried out to characterise the influence of rheological behaviour. In solvent systems skin permeation values of ACV increase as the concentration of PG increase yielding a maximum enhancement ratio (ER = 10) for 70% PG. The release rate of ACV from gels was determined. Higuchi's model was used to estimate the apparent diffusion coefficient of the drug. These values show a decrease as the content of PG in the vehicle increases; this effect could be attributed to the increase of the viscosity in the diffusional pathway. When gels are used skin permeation values of ACV were smaller than those of the solvent systems. This could be attributed to the network structure created by the polymer that increases the length of the diffusional pathway. The maximum ER (= 6.8) was for Carbopol gel containing 50% PG. Therefore, these gels can be considered candidates for further research to confirm their usefulness as delivery systems for ACV topical formulations.

In vitro release studies of piroxicam from oil-in-water creams and hydroalcoholic gel topical formulations

The importance of piroxicam, a therapeutic anti-inflammatory drug, is well known. Because of gastrointestinal disorders, dermatological dosage forms are recommended most. In our first studies, oil-in-water (O/W) creams of piroxicam (1% concentration) were prepared using glyceryl monostearate (GMS), stearic acid, and triethanolamine as additive ingredients. In our second studies, hydroalcoholic transparent gel formulations of this drug in a 0.5% concentration were prepared using hydroxypropylcellulose (HPC) as the gelling agent. The release of piroxicam from all formulations via dialysis through a cellulose membrane into phosphate buffer pH 6.8 at 37 degrees C was studied. The effects of additives such as propylene glycol and 2-propanol on the drug release were also investigated. The release profiles from the standpoint of diffusion-controlled processes, as well as zero-order and first-order kinetics, were evaluated, and relevant parameters, such as diffusion coefficient, permeability coefficient, and partition coefficient, were calculated. The release obeys both the diffusion mechanism and first-order kinetics. The drug release from gel formulations containing 10%, 20%, and 30% propylene glycol was decreased due to the enhancement of viscosity. However, the limpidity of these formulations was improved. Moreover, the release of drug from gel formulations containing 15% and 20% of 2-propanol was increased. These results show that a hydroalcoholic gel formulation with HPC is a more suitable preparation of piroxicam when compared with an O/W cream formulation.

Influence of propylene glycol and isopropyl myristate on the in vitro percutaneous penetration of diclofenac sodium from carbopol gels

The influence of propylene glycol (PG) on the in vitro penetration of diclofenac sodium (DFS) through a synthetic membrane and abdominal rat skin from carbopol gels was investigated using Franz-type diffusion cells. The combined effect of isopropyl myristate (IPM) and PG was also evaluated. It was found that the penetration through the synthetic membrane was well described by the Higuchi model. The gel containing 40% PG showed the highest release rate, indicating that a releasing maximum exists for PG content which provides the fully solubilized drug in the vehicle. When using rat skin as the barrier, the penetration rate was controlled by the membrane. DFS flux decreased with increasing PG content of the gels due to an increase of the drug affinity to the vehicle. A cosolvent action of PG was evident. However, the combination of PG and IPM resulted in a synergistic enhancement of DFS flux. Maximum enhancing activity was obtained from gels containing 40% PG, which yielded an enhancement ratio of about 8. Increasing IPM content from 3 to 5% increased the flux and decreased the lag time taken to reach a steady-state level.