Ketoprofen: release from, permeation across and rheology of simple gel formulations that simulate increasing dryness

Design and development of a novel fused filament fabrication (FFF) 3D printed diffusion cell with UV imaging capabilities to characterise permeation in pharmaceutical formulations

The present work aimed at designing and developing a novel 3D printed diffusion cell capable of UV imaging using the fused filament fabrication (FFF) method. UV imaging has proven to be very versatile in the area of pharmaceutics giving insights into various phenomena including the dissolution behaviour of dosage forms, intrinsic dissolution rates and the drug precipitation processes. A 3D printed diffusion cell in the similitude of a Franz cell was successfully printed using polylactic acid (PLA) filaments equipped with quartz for the imaging area. A model ibuprofen (IBU) gel formulation was tested by introducing the dosage form through the 3D printed donor compartment. The drug concentration permeated through the skin mimic (silicone membrane) was determined from the 3D printed receptor compartment using UV imaging in real-time. The results showed successful UV imaging of the permeation of IBU gel in the novel diffusion cell potentially negating further analytical testing such as the HPLC process required for Franz cell tests thereby reducing costs. Potential interactions between the drug and filament used in the 3D printed process suggests although this concept can be moved towards commercialisation, care should be taken with choice of filament used in the 3D printing process.

Ketoprofen-loaded polymer carriers in bigel formulation: an approach to enhancing drug photostability in topical application forms

The purpose of the study was to investigate the stability and biopharmaceutical characteristics of ketoprofen, loaded in polymeric carriers, which were included into a bigel in a semisolid dosage form. The polymer carriers with in situ-included ketoprofen were obtained by emulsifier-free emulsion polymerization of the monomers in aqueous medium or a solution of the polymers used. The morphological characteristics of the carriers, the in vitro release and the photochemical stability of ketoprofen were evaluated. The model with optimal characteristics was included in a bigel formulation. The bigel was characterized in terms of pH, rheological behavior, spreadability, and in vitro drug release. Acute skin toxicity, antinociceptive activity, anti-inflammatory activity, and antihyperalgesic effects of the prepared bigel with ketoprofen-loaded polymer carrier were evaluated. The carriers of ketoprofen were characterized by a high yield and drug loading. The particle size distribution varied widely according to the polymer used, and a sustained release was provided for up to 6 hours. The polymer mixture poly(vinyl acetate) and hydroxypropyl cellulose as a drug carrier, alone or included in the bigel composition, improved the photostability of the drug compared with unprotected ketoprofen. The bigel with ketoprofen-loaded particles provided sustained release of the drug and had optimal rheological parameters. In vivo experiments on the bigel showed no skin inflammation or irritation. Four hours after its application, a well-defined analgesic, anti-inflammatory, and antihyperalgesic effect was registered. The polymer mixture of poly(vinyl acetate) and hydroxypropyl cellulose as a carrier of ketoprofen and the bigel in which it was included provided an enhanced photostability and sustained drug release.

Direct estimation of the permeation of topical excipients through artificial membranes and human skin with non-invasive Terahertz time-domain techniques

BACKGROUND

Drug permeation through skin, or a synthetic membrane, from locally acting pharmaceutical products can be influenced by the permeation behaviour of pharmaceutical excipients.

OBJECTIVE

Terahertz time-domain technology is investigated as a non-invasive method for a direct and accurate measurement of excipients permeation through synthetic membranes or human skin.

METHODS

A series of in-vitro release and skin permeation experiments of liquid excipients (e.g. propylene glycol and polyethylene glycol 400) has been conducted with vertical diffusion cells. The permeation profiles of excipients through different synthetic membranes or skin were obtained using Terahertz pulses providing a direct measurement. Corresponding permeation flux and permeability coefficient values were calculated based on temporal changes of the terahertz pulses.

RESULTS

The influence of different experimental conditions, such as the polarity of the membrane and the viscosity of the permeant, was assessed in release experiments. Specific transmembrane flux values of those excipients were directly calculated with statistical differences between cases. Finally, an attempt to estimate the skin permeation of propylene glycol with this technique was also achieved. All these permeation results were likely comparable to those obtained by other authors with usual analytical techniques.

CONCLUSION

Terahertz time-domain technology is shown to be a suitable technique for an accurate and non-destructive measurement of the permeation of liquid substances through different synthetic membranes or even human skin.

Effects of solution chemistry on adsorption of selected pharmaceuticals and personal care products (PPCPs) by graphenes and carbon nanotubes

Adsorption of three selected pharmaceuticals and personal care products (PPCPs) (ketoprofen (KEP), carbamazepine (CBZ), and bisphenol A (BPA)) by two reduced graphene oxides (rGO1 and rGO2) and one commercial graphene was examined under different solution conditions. Single-walled carbon nanotubes (SWCNTs), multiwalled carbon nanotubes (MWCNTs), and powdered graphite were also investigated for comparison. All adsorption isotherms followed the order of SWCNTs > rGO1 > rGO2 > MWCNTs > graphene > graphite, consistent with the orders of their surface areas and micropore volumes. After surface area normalization, adsorption affinities of the three PPCPs onto graphenes were lower than onto graphite, suggesting incomplete occupation for adsorption sites because of the aggregation of graphene sheets and the presence of oxygen-containing functional groups. The observed pH effects on adsorption correlated well with the pH-regulated distribution of the protonated neutral species of the three PPCPs. Increasing ionic strength from 0 to 20 mM increased KEP adsorption due to the electrostatic screening by Na(+) and Ca(2+). Both humic acid (HA) and sodium dodecylbenzenesulfonate (SDBS) suppressed PPCPs adsorption to all adsorbents, but their impacts onto graphenes were lower than those onto CNTs because of their lower adsorption by graphenes. More severe HA (or SDBS) effect was found on negatively charged KEP at the tested solution pH 6.50 due to the electrostatic repulsion between the same charged KEP and HA (or SDBS). The findings of the present study may have significant implications for the environmental fate assessment of PPCPs and graphene.

Polypeptide-based aerosol nanoparticles: self-assembly and control of conformation by solvent and thermal annealing

Nanoconfined self-assemblies within aerosol nanoparticles and control of the secondary structures are shown here upon ionically complexing poly(L-lysine) (PLL) with dodecylbenzenesulfonic acid (DBSA) surfactant and using solvents chloroform, 1-propanol, or dimethylformamide. Different solvent volatilities and drying temperatures allowed tuning the kinetics of morphology formation. The supramolecular self-assembly and morphology were studied using cryo-TEM and SEM, and the secondary structures, using FT-IR. Highly volatile chloroform led to the major fraction of α-helical conformation of PLL(DBSA), whereas less volatile solvents or higher drying temperatures led to the increasing fraction of β-sheets. Added drugs budesonide and ketoprofen prevented β-sheet formation and studied PLL(DBSA)-drug nanoparticles were in the α-helical conformation. Preliminary studies showed that ketoprofen released with a slower rate than budesonide which was hypothesized to result from different localization of drugs within the PLL(DBSA) nanoparticles. These results instruct to prepare polypeptide aerosol nanoparticles with internal self-assembled structures and to control the secondary structures by aerosol solvent annealing, which we foresee to be useful, e.g., toward controlling the release of poorly soluble drug molecules.

Microbicide dosage forms

Microbicides are topically applied, user controlled dosage forms that are being developed to prevent the transmission of HIV during coitus. Early candidates focused on coitally dependent dosage forms such as gels and creams. More recent development has focused on broadening the coitally dependent options through the introduction of films and fast dissolving tablets. Additionally, it has become important to have longer acting products to minimize the burden of user compliance and thus vaginal rings have been developed providing sustained delivery of antiretroviral drugs. This chapter discusses the history of microbicides along with a detailed description of coitally dependent products, gels, films, tablets diaphragms, as well as coitally independent dosage forms such as vaginal rings and the introduction of a new technology, electrospun fibers.

Active compounds release from semisolid dosage forms

The aim of this paper is to review all the aspects of the in vitro release testing (IVRT) from semisolid dosage forms. Although none of the official dissolution methods has been specified for use with semisolid dosage forms, their utility for assessing release rates of drugs from semisolid dosage forms has become a topic of considerable interest. One can expect to overcome such complexity in the future, when the official "Topical and Transdermal Drug Products-Product Performance Tests" will be published in an issue of the Pharmacopeial Forum. Many factors such as type of the dissolution medium, membrane, temperature, and speed have an influence on the mechanism and kinetics of the release testing from gels, creams, and ointments; therefore, those parameters have been widely discussed.

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.

Preparation of Coated Valproic Acid and Sodium Valproate Sustained-release Matrix Tablets

The aim of this research was to investigate the technique for preparation of coated valproic acid and sodium valproate sustained-release matrix tablets. Different diluents were tested and selected as the effective absorbent for oily valproic acid. Effect of the amount of absorbent and hydroxypropylmethylcellulose on drug release from valproic acid-sodium valproate matrix tablets prepared with wet granulation technique was evaluated in pH change system. Colloidal silicon dioxide effectively adsorbed liquid valproic acid during wet granulation and granule preparation. The amounts of colloidal silicon dioxide and hydroxypropylmethylcellulose employed in tablet formulations affected drug release from the tablets. The drug release was prominently sustained for over 12 h using hydroxypropylmethylcellulose-based hydrophilic matrix system. The mechanism of drug release through the matrix polymer was a diffusion control. The drug release profile of the developed matrix tablet was similar to Depakine Chrono^®, providing the values of similarity factor (f2) and difference factor (f1) of 85.56 and 2.37, respectively. Eudragit^® L 30 D-55 was used as effective subcoating material for core matrix tablets before over coating with hydroxypropylmethylcellulose film with organic base solvent. Drug release profile of coated matrix tablet was almost similar to that of Depakine Chrono^®.

In-vitro transcutaneous delivery of ketoprofen and polyunsaturated fatty acids from a pluronic lecithin organogel vehicle containing fish oil

This work explored the use of pluronic lecithin organogel (PLO) as a base for the delivery of bioactive polyunsaturated fatty acids from fish oil, eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and ketoprofen. PLO was adapted to contain fish oil, ketoprofen, or both, and 1,8-cineole as penetration enhancer, and used to determine the in-vitro permeation from infinite and finite dosing protocols across full thickness porcine skin. Oruvail gel (2.5% ketoprofen) was included for comparison. No EPA or DHA was found to permeate skin when applied as an infinite dose. From multiple finite doses, small amount (max. 0.22%) of fish oil were found to permeate the skin. This indicates retention of fish oil within the gel matrix and that the viable domain of full thickness skin was a significant barrier. Greater amounts of EPA and DHA were delivered in the presence of ketoprofen indicating co-transport resulting from selective complexation, although no enhancement was observed using 1,8-cineole. Unlike EPA and DHA, substantial amounts of ketoprofen permeated when applied as infinite doses. Oruvail, a Carbopol 940-based hydrogel containing 2.5% ketoprofen and ethanol, delivered the greatest amount, although similar to the PLO gel containing 5% ketoprofen. The addition of propylene glycol enhanced permeation, although the presence of fish oil in the PLO gel inhibited ketoprofen permeation. When applied as multiple finite doses a maximum of 76μmcm2 (1.12%) was delivered, which was reduced by the presence of 1,8-cineole. Greater permeation was again observed with Oruvail by a factor of two and with half the ketoprofen dose. To conclude, a PLO-based gel is capable of delivering EPA and DHA via a repeat finite dosing regimen, although there is evidence for the retention of these very lipophilic molecules within the gel matrix. Although to a lesser extent than EPA and DHA, ketoprofen was also substantially retained, as exemplified by the superior delivery rates from Oruvail. Finally, this work has highlighted the importance of using an appropriate topical dosing method to match the intended use of a product.

In vitro delivery of anti-breast cancer agents directly via the mammary papilla (nipple)

The objective of this study was to investigate, in vitro, the plausibility of a novel method for delivering a combination of anti-breast cancer agents to the breast via the mammary papilla (nipple). Mammary papillae were prepared from freshly excised strips of porcine sow breasts by blunt dissection. Permeation studies were performed using all glass Franz diffusion cells in both upright and lateral position, with drugs examined individually and in combination. Donor phase was comprised of equimolar PD98059, LY294002 and tamoxifen; 2.54x10(-4) mol dissolved in 950 microL fish oil (containing approximately 23% (w/v) eicosapentaenoic acid, EPA), 25 microL DMSO and 25 microL 1,8-cineole. Also, 4 or 10% Cabosil M5P (w/v) was added to thicken the formulation. After 6 h, the papillae were recovered, cleaned, centrifuged and extracted thrice with methanol. Pooled extracts were analysed by reversed-phase HPLC. The significance of the papilla orientation was also investigated. When applied singly and laterally, the amount extracted from the porcine breast tissue for PD98059, LY294002 and tamoxifen were 1.83+/-0.30, 10.67+/-1.78 and 0.74+/-0.19x10(-2) micromol g(-1) respectively; applied simultaneously and laterally, 2.03+/-0.14, 4.86+/-0.47 and 0.22+/-0.04x10(-2) micromol g(-1) respectively. With 4% Cabosil formulation, amount extracted for PD98059 and LY294002 were 5.71+/-0.95 and 9.91+/-0.92x10(-2) micromol g(-1) respectively; with 10% formulation, 2.64+/-0.5 and 3.90+/-0.78x10(-2) micromol g(-1) respectively. Tamoxifen was below its limit of detection in both Cabosil M5P formulations. To conclude, localized passive delivery via the mammary papilla is a plausible non-invasive means of delivering anti-breast cancer drugs directly to the breast, in levels that have previously been shown to markedly inhibit the growth of breast cancer cell lines, in vitro. The amounts deliverable may be influenced by differential interactions with the thickening agent and patient orientation.

Effects of Membrane Type and Liquid/Liquid Phase Boundary onIn VitroRelease of Ketoprofen from Gel Formulations

The aim of this study was to test the hypothesis that the most appropriate model for studying the diffusional release of an active from a topical formulation is one in which the membrane offers minimal resistance to release and involves a receptor phase that presents the least possible interfacial discontinuity. Using ketoprofen as the active, a series of simple gels were prepared consisting of PEG400 thickened with Cabosil M5. Using Franz-type diffusion cells, three different types of membrane (two porous and one non-porous) were compared, as were receptor phases of PEG400 (component of formulation) and PBS. Of the membranes tested only 0.2 microm nylon provided consistent first order kinetics for a range of gel consistencies, indicating negligible influence of the membrane. The non-porous silicone membrane did not show first order kinetic profile confirming the diffusional nature of such a membrane. From the non-thickened formulations, diffusional release into a receptor phase of PEG400 was some 3x that into PBS, whereas from the formulation thickened with 5% Cabosil M5, diffusional release into a receptor phase of PEG400 was 6x lower than that into PBS. Diffusional release into PBS did not follow first order kinetics while diffusion into PEG400 did, suggesting that the existence of a discontinuity affected the release process. Although the importance of zero-resistance membranes is of perhaps obvious importance, it is often not stated in the literature. The existence of phase/hydrodynamic boundaries in release studies can be a source of significant inaccuracy.

Formulation of an antispasmodic drug as a topical local anesthetic

Mebeverine hydrochloride, a spasmolytic agent on GIT smooth muscles, was reported to have a local anesthetic effect. Thus, it was desired in this study to formulate mebeverine HCl into a gel that could be used locally in the treatment of different oral painful conditions. Poloxamer 407 (P-407) was used as the base for this gel. Different additives were used to enhance drug release from the preparation while others were used to enhance the residence time for the preparation. Different formulae were characterized in terms of drug release and mucoadhesion. The formula which has shown the best compromise between the aforementioned parameters was selected for clinical evaluation in comparison to Lidocaine HCl gel and rheologically examined. The best drug release enhancer was cetrimide (0.005%, w/w), while hydroxypropylcellulose (0.5%, w/w) as a mucoadhesive additive has shown the best compromise between fast drug release and mucoadhesion. The gel formula (G) has shown a better pain reduction efficiency (p=0.0078) and longer duration (p=0.0313) than Lidocaine HCl gel. Histopathological examination has shown no change in the inflammatory cells count of rat oral mucosa. Therefore, it could be concluded that (G) is very promising as a local anesthetic preparation for the treatment of different oral painful conditions.

Gels as vaginal drug delivery systems

The vagina has been used as a mucosal drug delivery route for a long time. Its single characteristics can be either limitative or advantageous when drug delivery is considered. Gels are semi-solid, three-dimensional, polymeric matrices comprising small amounts of solid, dispersed in relatively large amounts of liquid, yet possessing more solid-like character. These systems have been used and are receiving a great deal of interest as vaginal drug delivery systems. Gels are versatile and have been used as delivery systems for microbicides, contraceptives, labour inducers, and other substances. Although somewhat neglected in clinical studies, pharmaceutical characterization of vaginal gels is an important step in order to optimize safety, efficacy and acceptability. Indeed, the simple formulation of a gel can lead to different performances of systems containing the same amount of active substances. Therefore, this paper discusses and summarizes current use and research of vaginal drug delivery systems based in gels.

Limonene GP1/PG organogel as a vehicle in transdermal delivery of haloperidol

Penetration enhancers are a classical means for improving transdermal drug delivery (TDD). Enhancers permeate into the skin and reversibly decrease the barrier resistance. Basically, our aim is to formulate a transdermal gel containing an appropriate enhancer for a controlled drug release. Terpenes, namely limonene, linalool and cineole, in propylene glycol (PG) were first investigated in vitro for their capacity to enhance the percutaneous release of an anti-psychotic drug, haloperidol (HP). Relative to oxygenated linalool and cineole, hydrocarbon limonene was more effective as a skin enhancer; it increased human skin permeability and decreased lag time. Limonene was thus incorporated in an organogel comprised of gelator GP1 and PG. This skin-friendly gel in a transdermal patch could act as a long-acting formulation that delivers HP at a sustained percutaneous rate. The microscopic framework of the organogel is a branched network of interlocking fibres. Varying the gelator content modulates the fibre density and gel stiffness, and presents different degrees of resistance to drug diffusion on the vehicle side. Rheological and permeation studies demonstrated that an increase in gelator concentration increased gel moduli and decreased drug flux simultaneously. The rheology of the gel matrix influenced drug release rate in a manner described by several experimentally-derived correlations.

Film drying and complexation effects in the simultaneous skin permeation of ketoprofen and propylene glycol from simple gel formulations

This work investigated the simultaneous permeation of ketoprofen and propylene glycol (PG) across pig ear skin from simple gel formulations administered under simulated in-use conditions. The aims were to quantify rates of permeation of both solvent and active, probe the effects of formulation drying and gain insight into drag/complexation interactions. Simple 3-component gels were formulated using a fixed amount of ketoprofen and hydroxypropyl cellulose thickener with decreasing content of solvent propylene glycol. Multiple finite (5 mg x 15 mg) doses were massaged over 24h into full thickness pig ear skin in vertical Franz-type diffusion cells. The permeation of ketoprofen was inversely proportional to the content of PG, whereas the permeation of PG was directly proportional, although the amount of PG permeated was always greater than ketoprofen, even from the driest gel practically achievable. In this state, the molar ratio of PG/ketoprofen was approximately 12, suggesting that this number of PG molecules constitutes the solvation cage of ketoprofen. Dragging/pulling effect extends throughout the skin and into the receptor compartment and probably the system, in an in vivo situation. Although PG may represent a worse case scenario given its well-documented skin permeation enhancement properties, it is probable that other solvents exert a similar effect on solutes across skin. A drying film will behave in different ways depending on the nature of both the thickener and solvent, where the outcomes are not readily predictable. It is important to account for the fate of all species administered from a topical formulation.

Polyamidoamine dendrimers used as solubility enhancers of ketoprofen

Ketoprofen is a non-steroidal anti-inflammatory drug which is not freely soluble in water and creates gastrointestinal problems. In the present study we investigated the potential of polyamidoamine (PAMAM) dendrimers to increase the solubility of ketoprofen. The effect of variables, such as pH condition, concentration and generation of dendrimer, has been investigated. The experimental results showed that the solubility of ketoprofen in the dendrimer solutions was proportional to dendrimer concentration. Under suitable conditions PAMAM dendrimers can be highly effective used to enhance the solubility of ketoprofen.

Preferential π–π complexation between tamoxifen and borage oil/γ linolenic acid: Transcutaneous delivery and NMR spectral modulation

The effect of different proportions of borage oil on the in vitro transcutaneous delivery of tamoxifen were studied, with the aim of developing a gel capable of the simultaneous delivery of tamoxifen and gamma linolenic acid across (breast) skin. Supplementary work probed 1H NMR spectral data for tamoxifen in the presence of different proportions of polyunsaturated or unsaturated fatty acids. Typical, non-aqueous gels were modified to contain 1% tamoxifen and three levels of borage oil ( approximately 25% gamma linolenic acid) and the transcutaneous delivery of both tamoxifen and GLA across full thickness skin determined in vitro. Both tamoxifen and gamma linolenic acid permeated the skin with the ratio of moles being consistent at approximately 4:1. This was irrespective of time, amount of borage oil contained in the formulation (above a minimum) and the presence of other (unsaturated) excipients: mineral oil, Miglyiol 810N, white soft paraffin, PEG400 and Cabosil M5. Dose-dependent downfield shifts of tamoxifen aromatic protons were observed in the presence of borage oil and linolenic acid (gamma and alpha), but not saturated triacyl glycerol. The permeation data suggested vehicular complexation between tamoxifen and polyunsaturated constituents of borage oil and that such complexes permeated the skin intact. The 1H NMR data supported the hypothesis that such complexation was a consequence of preferential pi-pi orbital interactions between the phenyl groups of tamoxifen and the multiple double bonds of GLA. The mechanism for the permeation of intact complexes across skin remains to be elucidated.

Solvent Content and Macroviscosity Effects on the in vitro Transcutaneous Delivery and Skin Distribution of Ketoprofen from Simple Gel Formulations

The effects of decreasing solvent content and macroviscosity of simple topical gel formulations on the transcutaneous delivery and distribution of ketoprofen through skin were studied. Simple topical gels, based on ketoprofen, PEG 400 and either Cabosil M-5 or hydroxypropylcellulose were formulated and applied to freshly excised pig ear skin in vitro. Receptor phase samples were taken to determine permeation and depth profiles of ketoprofen were constructed, following tape stripping and membrane separation. Reduction of solvent from the Cabosil-thickened gels resulted in a rank order reduction in the permeation and distribution of ketoprofen. Reduced amounts of ketoprofen were distributed through the skin, particularly the dermis, with decreasing solvent. Two gels sharing the same macroviscosity exhibited significantly different skin permeation and distribution characteristics. The rank order reduction in both permeation and distribution of ketoprofen was attributed to the physiochemical properties of the formulation and how they may change after application, in particular the increased adsorptivity of ketoprofen to the Cabosil relative to the amount of solvent present in the system. This effect appeared to be predominant over any interactions occurring between the formulation and the skin. The data provided further evidence that adsorption to the thickener, rather than changes in viscosity, were primarily responsible for reduced permeation and distribution in the system examined.

In vitro transdermal delivery of the major catechins and caffeine from extract of Camellia sinensis

The aim of this study was to investigate the feasibility of the transdermal delivery of catechins and caffeine from green tea extract. Drug-in-adhesive patches containing 1.35, 1.03, 0.68, and 0.32 mg cm(-2) green tea extract were formulated and the dissolution of (-)-epigallocatechin gallate (EGCg), (-)-epigallocatechin (EGC) and (-)-epicatechin (EC) from these was determined. Transdermal delivery was determined across full thickness pig ear skin from saturated solutions of green tea extract in pH 5.5 citrate-phosphate buffer, polyethylene glycol 400 and a 50:50 mixture of the citrate phosphate buffer and polyethylene glycol in addition to patches containing 1.35 mg cm(-2) green tea extract. Dissolution experiments indicated first order release which was dose dependent in respect of the loading level, although the amounts permeated were not always proportional to the amounts in the formulation. The highest percentage permeation of EGCg was found to be from the patch formulation. EGCg, EGC and EC were all successfully delivered transdermally from saturated solutions and adhesive patches containing green tea extract in this study. There was some evidence for the dermal metabolism of EGCg, but after 24 h 0.1% permeated from the patches containing 1.35 mg cm(-2) green tea extract. This was equivalent to the percentage absorbed after intragastric administration of green tea extract in rats. In addition, the concentration of EGCg in the Franz cell receptor chamber after 24 h permeation from the 0.9 cm diameter patch containing 1.35 mg cm(-2) was within the range of Cmax plasma levels achieved after oral dosing of 2.2-4.2 gm(-2) green tea extract. Caffeine was also delivered at concentrations above those previously reported.