Development and evaluation of occlusive systems employing polyvinyl alcohol for transdermal delivery of sumatriptan succinate

Development, characterization, and ex vivo evaluation of an insert for the ocular administration of progesterone

Progesterone (PG) affords neuroprotection in degenerative diseases associated to oxidative stress, such as cataracts, age-related macular degeneration, glaucoma, diabetic retinopathy and retinitis pigmentosa. The aim of this project was to develop ocular inserts for delivery of PG to the eye. Different inserts with PG in its composition were formulated and the insert with the best characteristics (59% polyvinyl alcohol, 39% polyvinylpyrrolidone K30 and 2% propylene glycol) was selected for ex vivo studies. Physical characteristics and drug release patterns of the insert were analysed. In vitro diffusion studies revealed a controlled diffusion of progesterone. Ex vivo experiments demonstrated similar trans-corneal and trans-scleral PG diffusion (corneal apparent permeability coefficient 6.46 ± 0.38 × 10^-7 cm/s and scleral apparent permeability coefficient 5.87 ± 1.18 × 10^-7 cm/s; mean ± SD; n = 5). However, the amount of PG accumulated in scleras was statistically higher than in corneas (30.07 ± 9.09 μg/cm² and 15.56 ± 4.36 μg/cm² respectively). The PG-loaded inserts (55.6 μg/cm²) were thin, translucent, showed no irritancy (HET-CAM test) and were elastic and robust, all suitable properties for its potential use in the treatment of several ocular diseases.

[Pharmaceutical Properties of Anti-inflammatory Analgesic Patches Using Acrylic Polymer]

The mock patches were prepared with novel acrylic polymers as adhesive layer where biphenyl-4-ylacetic acid (BAA) or 2-(2-fluorobiphenyl-4-yl) propanoic acid (FPA) was used as model active pharmaceutical ingredients (APIs). In addition, the mock patches were formulated with typical ester ingredients for transdermal dosage forms. The molecular state of the model APIs in the adhesive layer was observed by polarized microscope and microscopic Raman spectroscopy, which contains both conventional and low frequency (LF) region. Crystallization behavior would be depended on the interaction between API and polymers in the adhesive layer. In particular, LF Raman measurement was useful to discriminate API polymorphs. The pharmaceutical properties including dissolution and skin permeation of APIs were also evaluated for mock patches. The drug release and transdermal permeation were enhanced with the ester ingredients such as isopropyl myristate and diethyl sebacate due to their diffusion to the test solution or the skin stratum corneum as well as reducing the interaction between API and polymers. Further, the tack strength was not changed, but the peel strength was weakened by the additives. Thus, the adhesive properties were controllable by formulation with the additives. These findings could enable to evaluate the interaction between API and the polymers for adhesive layer and select the appropriate polymer and additives for used APIs when designing the drug products.

Using Microemulsion as Carrier for Drug Transdermal Delivery: The Effect of Surfactants and Cosurfactants

BACKGROUND

The purpose of this study was to evaluate the effect of types of surfactants and cosurfactants on physicochemical properties and permeability of sumatriptan-loaded microemulsions through rat skin.

METHODS

Different types of surfactants and cosurfactants were used to prepare drug-loaded microemulsions. The physicochemical characters and permeability parameters of these formulations were measured.

RESULTS

The experimental microemulsions with varying components had small droplet size ranging from 24.6 nm to 2568.8 nm, low viscosity ranging from 7.49 to 43.34 cps and significant permeation enhancement ratio ranging from 23.0 to 98.6 when compared to the control group.

CONCLUSION

The composition and proportion of surfactants and cosurfactants were key factors for the physiochemical properties of drug-loaded microemulsions. The cumulative transdermal amount of the microemulsion containing mixture surfactant of Laureth-3/Laureth-23 was higher than that of the microemulsion with a mixture of Tween 80/Span 20. In the selected cosurfactant, diethylene glycol monoethyl ether (DEGMEE) showed highest permeation enhancement. Thermodynamic stability tests revealed that the experimental microemulsion was a stable enough formulation to be considered as a suitable carrier for sumatriptan.

Transdermal therapeutic systems for memantine delivery. Comparison of passive and iontophoretic transport

Memantine is a non-competitive N-methyl-d-aspartate (NMDA) receptor antagonist used in the treatment of moderate to severe dementia including the symptoms of Alzheimer's disease (AD). It is administered orally but compliance, swallowing problems and the routine use of multiple medications in elderly AD patients means that an alternative route of administration would be of interest. The aim of the present study was to develop memantine hydrochloride occlusive transdermal therapeutic systems (TTS) for passive and iontophoretic delivery across the skin. Polyvinyl pyrrolidone (PVP) and a mixture with polyvinyl alcohol (PVA) were employed as polymeric matrices. The study involved the TTS characterization in addition to quantification of the memantine transport across porcine skin in vitro. The evaluation of the TTS physical properties suggested that systems were made more mechanically resistant by including PVA (6%) or high concentrations of PVP (24%). Moreover, a linear correlation was observed between the concentration of PVP and the bioadhesion of the systems. Drug delivery experiments showed that the highest transdermal flux provided by a passive TTS (PVP 24% w/w limonene) was 8.89±0.81μgcm^-2h^-1 whereas the highest iontophoretic transport was 46.4±3.6μgcm^-2h^-1. These innovative TTS would enable two dosage regimens that could lead to therapeutic plasma concentrations.

Development of antimigraine transdermal delivery systems of pizotifen malate

The aim of this study was to develop and evaluate a transdermal delivery system of pizotifen malate. Pizotifen is frequently used in the preventive treatment of migraine, but is also indicated in eating disorders. In the course of the project, the effects of chemical enhancers such as ethanol, 1,8-cineole, limonene, azone and different fatty acids (decanoic, decenoic, dodecanoic, linoleic and oleic acids) were determined, first using a pizotifen solution. Steady state flux, diffusion and partition parameters were estimated by fitting the Scheuplein equation to the data obtained. Among the chemical enhancers studied, decenoic acid showed the highest enhancement activity, which seemed to be due to the length of its alkyl chain and unsaturation at the 9th carbon. The influence of iontophoresis and the involvement of electrotransport in said process was determined. The absorption profile obtained with iontophoresis was similar to that obtained with fatty acids and terpenes, though skin deposition of the drug was lower with the former. Transdermal delivery systems (TDS) of pizotifen were manufactured by including chemical enhancers, decenoic acid or oleic acid, and were subsequently characterized. When the results obtained with solutions were compared with those obtained with the TDS, a positive enhancement effect was observed with the latter with respect to the partitioning and diffusion of the drug across the skin. Our findings endorse the suitability of our TDS for delivering therapeutic amounts of pizotifen malate.

Adhesive properties: a critical issue in transdermal patch development

INTRODUCTION

Transdermal patches and medicated plasters (patch) represent well-established prolonged release dosage forms. Even if satisfactory adhesion to the skin is strictly linked to the efficacy and safety of the therapeutic treatment, nowadays numerous reports of in vivo 'adhesion lacking' are still addressed to regulatory agencies. The adhesive properties of a patch should be characterized considering i) the ability to form a bond with the surface of another material on brief contact and under light pressure (tack); ii) the resistance of the adhesive to flow (shear adhesion); and iii) the force required to peel away a patch from a surface (peel adhesion).

AREAS COVERED

In this manuscript, the most widely used methods to measure adhesive properties during development studies are described, along with the quality control of patches. The influence of formulative variables on patch adhesive properties, and their possible relationship with the in vivo adhesion performances, is also discussed.

EXPERT OPINION

The Pharmacopoeias should consider the opportunity of introducing compendial testing to assay the quality of adhesive patch properties, and regulatory agencies should issue proper guidelines to evaluate these features during development.