Towards the Continuous Manufacturing of Liquisolid Tablets Containing Simethicone and Loperamide Hydrochloride with the Use of a Twin-Screw Granulator

Continuous manufacturing is becoming the new technological standard in the pharmaceutical industry. In this work, a twin-screw processor was employed for the continuous production of liquisolid tablets containing either simethicone or a combination of simethicone with loperamide hydrochloride. Both active ingredients present major technological challenges, as simethicone is a liquid, oily substance, and loperamide hydrochloride was used in a very small amount (0.27% w/w). Despite these difficulties, the use of porous tribasic calcium phosphate as a carrier and the adjustment of the settings of the twin-screw processor enabled the optimization of the characteristics of the liquid-loaded powders and made it possible to efficiently produce liquisolid tablets with advantages in physical and functional properties. The application of chemical imaging by means of Raman spectroscopy allowed for the visualization of differences in the distribution of individual components of the formulations. This proved to be a very effective tool for identifying the optimum technology to produce a drug product.

Development of Safirinium dyes for new applications: fluorescent staining of bacteria, human kidney cells, and the horny layer of the epidermis

Low-molecular synthetic fluorophores are convenient tools in bioimaging applications. Several derivatives of Safirinium dyes as well as their reactive N-hydroxysuccinimide (NHS) esters bearing diverse substituents were synthesized and evaluated experimentally in terms of their lipophilicity by means of reverse-phase and immobilized artificial membrane high-performance liquid chromatography. Subsequently, the selected compounds were employed as novel cellular imaging agents for staining Gram-positive and Gram-negative bacteria, human kidney cell line, as well as human skin tissue. The analyzed dyes allowed for visualization of cellular structures such as mitochondria, endoplasmic reticulum, and cellular nuclei. They proved to be useful in fluorescent staining of stratum corneum, especially in the aspect of xenobiotic exposure and its penetration into the skin. The best results were obtained with the use of moderately lipophilic NHS esters of Safirinium Q. The development of Safirinium dyes is a promising alternative for commercially available dyes since the reported molecules have low molecular masses and exhibit efficient staining and remarkable water solubility. Moreover, they are relatively simple and low-cost in synthesis.

Comparative study of the percutaneous permeation and bioaccumulation of the cyclic siloxane using frozen-thawed and nonfrozen ex vivo human skin

Literature shows contradictory information regarding the effect of freezing the excise skin ex vivo on the diffusion of substances into the skin. Few studies indicate that storing the human or animal skin in a frozen state decreases the barrier properties after thawing. Therefore, to understand the properties of frozen skin, we evaluated the effect of storage of ex vivo human skin (2 weeks at -20 °C) on the penetration of stratum corneum and permeation into deeper skin layers (epidermis, and dermis) as well as to the receptor fluid by octamethylcyclotetrasiloxane (D4) a representative test compound of cyclic siloxanes. The main research were preceded by checking the integrity of nonfrozen ex vivo human skin in comparison to the frozen-thawed one by using the Electrical Resistance technique (ER) and the fluorescence microscopy. Samples collected in the skin absorption experiment were analyzed by gas chromatography equipped with a flame ionization detector (GC-FID). The results of this study demonstrated that freezing of excised ex vivo human skin at -20 °C for up to 14 days does not alter the permeability of D4 in a statistically significant manner. Thus, our results confirmed the validity of using skin storage conditions for testing the penetration and permeation of xenobiotics recommended by the OECD, EMA, and WHO guidelines.

Potential of mucoadhesive chitosan glutamate microparticles as microbicide carriers - antiherpes activity and penetration behavior across the human vaginal epithelium

Chitosan glutamate (gCS) spray-dried microparticles appear promising carriers to overcome challenges associated with vaginal microbicide delivery. This study aimed at elucidating the penetration and mucoadhesive behavior of developed gCS multiunit carriers with zidovudine (ZVD) as a model antiretroviral agent in contact with excised human vaginal epithelium followed with an examination of in vitro antiherpes activity in immortal human keratinocytes HaCaT and human vaginal epithelial cells VK2-E6/E7. Both ZVD dispersion and placebo microparticles served as controls. Microparticles displayed feasible (comparable to commercial vaginal product) mucoadhesive and mucoretention characteristics to isolated human vaginal tissue. Ex vivo penetration studies revealed that gCS increased the accumulation of active agent in the vaginal epithelium but surprisingly did not facilitate its penetration across human tissue. Finally, the obtained antiviral results demonstrated the potential of gCS as an antiherpes adjunctive, whose mode of action was related to blocking viral attachment.

Development of a Biphasic-Release Multiple-Unit Pellet System with Diclofenac Sodium Using Novel Calcium Phosphate-Based Starter Pellets

Novel calcium phosphate-based starter pellets were used to develop a biphasic-release multiple-unit pellet system (MUPS) with diclofenac sodium as a model drug in the form of hard gelatin capsules. For comparative purposes, corresponding formulations based on the inert cores made of microcrystalline cellulose, sucrose and isomalt were prepared. The developed system consisted of two types of drug-layered pellets attaining different release patterns: delayed-release (enteric-coated) and extended-release. Dissolution characteristics were examined using both compendial and biorelevant methods, which reflected fed and fasting conditions. The results were collated with an equivalent commercial product but prepared with the direct pelletization technique.

Transdermal transport of collagen and hyaluronic acid using water in oil microemulsion

Collagen and hyaluronic acid (HA) are biopolymers that affect the appearance and condition of the skin. Delivery of these compounds into the skin is highly challenging since have a number of disadvantageous properties, such as high molecular weight and hydrophilicity. Here, we evaluated the transdermal penetration of low and high molecular weight collagen and HA from microemulsions. A number of microemulsion formulations, differing in the content of polymers and surfactants (i.e. penetration promoters), were used for the permeation study. In addition, a correlation was made between the composition of these microemulsions and the polymers transport efficiency. The results indicate that, microemulsions enable transdermal permeation of collagen and HA. The concentration of polymers and the solubilization capacity of microemulsions had the greatest influence on the permeation. Surprisingly, the molecular weight of polymers and the content of other components affected the size of microemulsion particles, and thus these parameters had an indirect influence on the permeation process. This study demonstrated therefore the potential therapeutic use of microemulsion with collagen and HA in improving and regenerating the barrier of aged or diseased skin.

The consequences of overcoming the human skin barrier by siloxanes (silicones) Part 1. Penetration and permeation depth study of cyclic methyl siloxanes

Dynamic production of cyclic siloxanes: octamethylcyclotetrasiloxane D4, decamethylcyclopentasiloxane D5 and dodecamethylcyclohexasiloxane D6 increases their concentrations in environment. It is considered that both environmental pollution and the usage of personal care products and cosmetics containing cyclic siloxanes can be the main source of the human exposure by transdermal route. The aim of the study was to verify the possibility to overcome the skin barrier by cyclic siloxanes (ATR-FTIR and GC-FID), evaluation of diffusion pathway to stratum corneum SC (Fluorescence microscopy), and determination of depth of permeation to deeper skin layers: epidermis and dermis (ATR-FTIR) and also of potential interaction with SC lipids and proteins (Fluorescence microscopy, ATR-FTIR) and the cytotoxicity studies against HaCaT cells (MTT test). The results show that D4, D5 and D5 can penetrate to SC and permeate into the deeper layers of the skin: epidermis and dermis. The quantitative analysis (GC-FID) showed that total cumulative doses for D4, D5 and D6 were: 42.50; 95.37 and 77.19 μg/cm2/24 h, respectively. The microscopic analysis proved, transepidermal route through the lipid matrix as well as through the canyons (intercluster spaces) were a diffusion pathway to the SC as well as disruption of human SC lipid structure by: D4 (the most), D5 and D6 (the least). The cytotoxicity studies demonstrated that the tested range of concentrations of D5 and D6 (up to 300 mM, 111 300 mg and 133 500 mg respectively) did not impaired the HaCaT growth, while D4 had IC50 value of 40 098 mM ± 7.94 (10 906 ± 872,5 mg).

Dissolution studies of metamizole sodium and pseudoephedrine sulphate dosage forms - comparison and correlation of electronic tongue results with reference studies

This work reports a critical evaluation of the results of the release of active substances (APIs) from novel pharmaceutical formulations provided by an electronic tongue system (ET). Detailed dissolution studies of modified-release granules used in pharmacotherapy containing metamizole sodium and pseudoephedrine sulphate were carried out. The impact of the dissolution-modifying excipients (carmellose sodium and hypromellose) on the dissolution process as well as on the outcomes of the sensor array of ion-selective electrodes was investigated. The obtained dissolution profiles were compared and correlated with those registered during the reference studies performed according to the pharmacopoeial method. It was pointed out that the proper evaluation of the efficiency of the release modification requires the examination of dosage forms as well as physical mixtures of API and excipient. Moreover, the results obtained using potentiometric ET were complementary to the classical methodology. Their partial inconsistency, remarked during several experiments, should be interpreted with caution owing to simultaneous sensing of APIs and excipients by the sensors and their various performances (i.e. selectivity and sensitivity) towards these components.

The effect of mangiferin on skin: Penetration, permeation and inhibition of ECM enzymes

Mangiferin (2-C-β-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone) is a polyphenol with strong antioxidant properties. Mangiferin is obtained from the mango tree (Mangifera indica L., Anacardiaceae). It has been proven that mangiferin exhibits many pharmacological activities. The aim of this study was to analyze the penetration of mangiferin into the human skin and through the skin. According to our knowledge, skin penetration and permeation studies of mangiferin have not been analyzed so far. Additionally, the influence of mangiferin on two Extracellular Matrix Enzymes (ECM): collagenase and elastase, was evaluated for the first time. It has been indicated that mangiferin is able to permeate the stratum corneum and penetrate into the epidermis and dermis in comparable amounts. For confirmation of the obtained results, fluorescence microscopy was successfully utilized. The analysis revealed the capability of mangiferin to reversibly inhibit elastase and collagenase activity. The mechanism of mangiferin interaction with both enzymes was estimated as a noncompetitive inhibition.

Influence of dissolution-modifying excipients in various pharmaceutical formulations on electronic tongue results

The overall performance of a potentiometric electronic tongue (ET) as well as the sensitivity and selectivity pattern of particular ion-selective electrodes forming the array towards exemplary APIs (metamizole sodium, pseudoephedrine sulphate) and excipients (hypromellose, carmellose, Eudragit E) was determined. Simultaneous sensing of both API and the encapsulating excipient in their physical mixture was noticed using potentiometric sensors. Usually, such altering of chemical image is treated as an evidence of taste masking/modified release effect (linked with chemical entrapment of API in polymer matrix), while the observed "mixture effect" can also take place which may complicate the interpretation of ET results. Moreover, the influence of the same excipients on chemical images of various APIs was compared and related to sensor array performance. The presented considerations should be taken into account in the case of ET assessment of drug dissolution profiles and detection of modified release effect, especially when novel drug delivery systems are considered.

The improvement of the dissolution rate of ziprasidone free base from solid oral formulations

This work aims at increasing solubility and dissolution rate of ziprasidone free base-Biopharmaceutics Classifaction System (BCS) class II compound. The authors describe a practical approach to amorphization and highlight problems that may occur during the development of formulations containing amorphous ziprasidone, which was obtained by grinding in high-energy planetary ball mills or cryogenic mills. The release of ziprasidone free base from the developed formulations was compared to the reference drug product containing crystalline ziprasidone hydrochloride-Zeldox® hard gelatin capsules. All preparations were investigated using compendial tests (USP apparatuses II and IV) as well as novel, biorelevant dissolution tests. The novel test methods simulate additional elements of mechanical and hydrodynamic stresses, which have an impact on solid oral dosage forms, especially during gastric emptying. This step may prove to be particularly important for many formulations of BCS class II drugs that are often characterized by narrow absorption window, such as ziprasidone. The dissolution rate of the developed ziprasidone free base preparations was found to be comparable or even higher than in the case of the reference formulation containing ziprasidone hydrochloride, whose water solubility is about 400 times higher than its free base.

Determination of API content in a pilot-scale blending by near-infrared spectroscopy as a first step method to process line implementation

Near infrared (NIR) spectroscopy was used for estimation of powder blend homogeneity and manufacturing control of a medicinal product powder mixture containing active pharmaceutical ingredient (API). Aiming at initiating a Process Analytical Technology (PAT) activity, the first step was a stationary mode at-line evaluation. In this, the content of pharmaceutical active compound in the powder mixtures intended to the direct tabletting was estimated based on recorded NIR spectra. Five formulations containing different quantities of API were prepared and analyzed also by a reference method--UV-Vis spectroscopy. A chemometric model was developed for calculation of the API amount in the mixtures. The Principal Component Regression (PCR) and Partial Least Squares (PLS) algorithms were used to obtain a model useful in further implementation for the PAT recommendations, into in-line blending control.

Development of rapid and robust stability-indicating method for analysis of ziprasidone (hydrochloride and freebase) as drug substance and in medicines by UPLC

Ultra Performance Liquid Chromatography (UPLC) was employed to develop a rapid and robust method for the analysis of ziprasidone, both as a drug substance and in the final dosage forms. The application of this method in stability analyses was verified. Tests were carried out according to ICH/FDA guidelines, European Pharmacopeia, and United States Pharmacopeia rules, which take into account factors such as specificity, linearity, accuracy, and precision. Separation was performed on an Acquity UPLC BEH phenyl 1.7-microm column with a simple mobile phase, consisting of acetonitrile and water adjusted to pH 2.0 with ortho-phosphoric acid. Using this mobile phase and gradient elution, the separation was completed within 5 min. This method is very sensitive, and allows performing simultaneous identification, assay, and determination of impurities and related substances in one injection.

Taste masking of roxithromycin by spray drying technique

The spray drying technique was used to obtain the roxithromycin containing microcapsules with high taste masking efficiency. Eudragit L30D-55 was chosen as a barrier coating. The taste was evaluated by an electronic tongue, and taste-masking effect in water lasted at least several dozen hours.

Electronic tongue for the detection of taste-masking microencapsulation of active pharmaceutical substances

Electronic tongues can produce chemical images of samples, whose changes can be correlated with general properties, e.g. taste sensations. In this work, a sensor array equipped with eight types of ion-selective electrodes was coupled with Principal Components Analysis in order to detect microencapsulation effect of two Active Pharmaceutical Ingredients (APIs), which influences their taste properties. The character of change of sensor array responses in samples modified by microencapsulation was the same in two investigated APIs (Ibuprofen and Rixithromycin), proving, that the "sensed taste" becomes similar in both formulations after Eudragit modification. The obtained results show, that the presented electronic tongue can be used for analysis of masking effects in drugs and detection of microencapsulation effect.

Spray drying technique: II. Current applications in pharmaceutical technology

This review presents current applications of spray drying in pharmaceutical technology. The topics discussed include the obtention of excipients and cospray dried composites, methods for increasing the aqueous solubility and bioavailability of active substances, and modified release profiles from spray-dried particles. This review also describes the use of the spray drying technique in the context of biological therapies, such as the spray drying of proteins, inhalable powders, and viable organisms, and the modification of the physical properties of dry plant extracts.

Magnetic resonance imaging of the skin

A thorough examination of the skin is essential to screen various diseases accurately, evaluate the effectiveness of topically applied drugs and assess the results of dermatological surgeries such as skin grafts. The assessment of skin properties is also crucial in the cosmetics industry, where it is important to evaluate the effects skin care products have on these properties. The simplest and most widely used method of skin evaluation, the 'naked eye' assessment, enables researchers to assess only the skin surface and involves a large amount of inter-observer variability. Thanks to a great progress that has been made in physics, electronics and computer engineering in recent years, sophisticated imaging methods are increasingly available in day-to-day studies. The aim of this review was to present one of these techniques, namely the magnetic resonance imaging (MRI), and to discuss its possible use in skin examination and analysis. We present basic principles of MRI, as well as several interesting applications in the field of dermatology, and discuss the advantages and limitations of this method.

Ex vivo skin absorption of terpenes from Vicks VapoRub ointment

BACKGROUND

The pharmaceutical market offers a wide range of inhalant drug products applied on the skin that contain essential oils and/or their isolated compounds, i.e. terpenes. Because there are few data concerning the skin penetration of terpenes, especially from complex carriers, the goal of this study was to determine the ex vivo skin absorption kinetics of chosen terpenes, namely eucalyptol, menthol, camphor, alpha-pinene, and beta-pinene, from the product Vicks VapoRub.

MATERIAL/METHODS

Human cadaver skin was placed in a flow-through diffusion chamber and the product was applied for 15, 30, and 60 min. After the application time the skin was separated into layers using a tape-stripping technique: three fractions of stratum corneum and epidermis with dermis, and terpenes amounts in the samples were determined by gas-chromatography.

RESULTS

The investigated terpenes showed different absorption characteristics related to their physicochemical properties and did not permeate through the skin into the acceptor fluid. Eucalyptol had the largest total accumulation in the stratum corneum and in the epidermis with dermis, while alpha-pinene penetrated into the skin in the smallest amount.

CONCLUSIONS

The short time in which saturation of the stratum corneum with the terpenes occurred and the high accumulation of most of the investigated terpenes in the skin layers proved that these compounds easily penetrate and permeate the stratum corneum and that in vivo they may easily penetrate into the blood circulation.

Use of cyclodextrins in topical formulations: Practical aspects

Cyclodextrins are promising, but using them as an excipients can sometimes be difficult. The aim of this review is to summarize the results of recent studies on the application of parent cyclodextrins (alpha-, beta-, gamma-) and some of their derivatives in topical formulations. General properties, current legal status, and toxicological aspects of cyclodextrins are briefly described. The goal of using cyclodextrins to create new formulations with well-known actives, advantages, and limitations in topical formulations is presented, and possible applications in such preparations are also discussed.

Commentary to the article "Human skin penetration of the major components of Australian tea tree oil applied in its pure form and as a 20% solution in vitro"

This note summarises recent studies on skin penetration of terpinen-4-ol, which is the main component of tea tree oil [S.E. Cross, M. Russell, I. Southwell, M.S. Roberts, Human skin penetration of the major components of Australian tea tree oil applied in its pure form and as a 20% solution in vitro, Eur. J. Pharm. Biopharm. doi: 10.1016/j.ejpb.2007.10.002 (in press)]. The influence of different experimental models on obtained skin penetration results is discussed.

Aqueous Solubility of Liquid Monoterpenes at 293 K and Relationship with Calculated Log P Value

Aqueous solubility is often a limiting factor in any concentration-dependent process and n-octanol/water partition coefficient, usually expressed as log P, is equilibrium between surrogate of nonaqueous biophases and water phase. The aqueous solubility of seven liquid monoterpenes: (+/-)-beta-citronellol, (+/-)-linalool, linalyl acetate, (-)-alpha-pinene, (-)-beta-pinene, eucalyptol and terpinen-4-ol were experimentally determined at 293 K. The obtained aqueous solubility data correlate well with log P values calculated by ACD/Log P software.

Skin penetration of terpenes from essential oils and topical vehicles

The purpose of this study was to evaluate the in vitro cutaneous penetration of five terpenes--linalool, linalyl acetate, terpinen-4-ol, citronellol and alpha-pinene--applied in pure essential oils or in dermatological formulations (o/w emulsion, oily solution or hydrogel) containing 0.75 % w/w of the essential oils. Different skin absorption was observed depending on the type of the vehicle and terpenes' log P values. Cutaneous accumulation of terpenes is several times higher when they are applied in pure essential oils than in topical vehicles. Penetration of terpinen-4-ol to the skin was better from an oily solution (approximately 90 microg/cm (2)) than from an emulsion (60 microg/cm (2)). No penetration of linalyl acetate from topical vehicles into viable skin was observed, but also for this terpene penetration to the upper layers of the stratum corneum was 2-times higher when an oily solution was used. In contrast, the cutaneous absorption of linalool was the same from both vehicles (50-60 microg/cm (2)). The skin penetration of alpha-pinene was not traceable when it was applied in an oily solution. Only a small amount (approximately 5 microg/cm (2)) of this terpene was determined in viable skin after application as a hydrogel. Citronellol applied in a hydrogel penetrated into all skin layers in a total amount of 25 microg/cm (2), while no penetration into viable skin layers after application of an oily solution was noted. Only citronellol permeated into the acceptor medium.

Effect of physicochemical properties of cyclic terpenes on their ex vivo skin absorption and elimination kinetics

BACKGROUND

The terpenes disturb lipid arrangement in the intercellular region of the stratum corneum (SC) that leads to the increased permeability of the skin. This effect is used in technology of transdermal drug forms and depends on physicochemical properties of terpenes and their amounts penetrated to the stratum corneum; however terpenes do not need penetrate into viable skin tissue and this event is not even desired.

OBJECTIVE

To correlate skin absorption and elimination kinetics of four cyclic terpenes, namely alpha-pinene, beta-pinene, eucalyptol and terpinen-4-ol, applied as neat substance with their physicochemical properties.

METHODS

The terpenes were applied onto the human skin in vitro, and after 1-4 h their content in the separated by a tape-stripping method stratum corneum layers and in the epidermis/dermis was determined using GC. Similarly, the amounts of terpenes in the skin were analysed during 4 h following 1 h absorption.

RESULTS

The fastest and progressive penetration into all skin layers was observed for terpinen-4-ol. All studied terpenes are absorbed in the viable epidermis/dermis, however penetration into this layers is time-dependent process, constantly increasing during 4 h. Like for stratum corneum, the largest cumulation in epidermis/dermis was observed for terpinen-4-ol. The elimination of terpenes from the stratum corneum was fast, especially in deeper layers, and much faster if the initial cumulation was small.

CONCLUSION

Investigated cyclic terpenes represent different penetration and elimination characteristics and do not permeate across the skin to the acceptor medium due to large cumulation in the skin tissue. The penetration of terpenes into stratum corneum is greater if their log P-value is close to 3.

How does the type of vehicle influence the in vitro skin absorption and elimination kinetics of terpenes?

Terpenes are widely used in the topical dermal preparations, cosmetics and toiletries and also in the experimental dermopharmacy, as penetration enhancers. Terpenes do not need to penetrate into viable skin tissue and this event is not even desired. The aim of this study was to investigate skin absorption and elimination kinetics of two terpenes, namely linalool and terpinen-4-ol, incorporated in three different dermatological vehicles: oily solution, hydrogel and o/w emulsion. The preparations were applied onto the human skin in vitro, and after 1-4 h the content of terpenes in the stratum corneum layers and in the epidermis/dermis was determined using GC. Similarly, the amounts of terpenes in the skin were analysed during 4 h elimination process following 1 h absorption. The highest skin absorption was observed when terpenes were applied in hydrogel--their total content in the skin after 4 h was 385 and 705 microg/cm2 for linalool and terpinen-4-ol, respectively. After 1 h of the elimination process about 10-20% drop of the total content of both terpenes in the skin was noted for all formulations. The skin penetration of both terpenes from the vehicles is increasing in the following order: emulsion < oily solution < hydrogel, while the elimination phase is relatively slower for terpenes applied in hydrogel.

Development of modified-release dosage forms containing loratadine and pseudoephedrine sulfate

Pseudoephedrine sulfate (PES) is a short-acting sympathomimetic amine and decongestant. Loratadine (L) is a long-acting antihistamine, H1 blocker. These drugs administered together provide relief from a whole range of rhinitis (hay fever) symptoms. Combination of both drugs is available in the form of sugar-coated modified-release tablets Clarinase (Schering-Plough). In this product, 5 mg of L and 60 mg of PES is present in the sugar-coating layer ready for an immediate release, and the rest of PES (60 mg) is incorporated in the extended-release core of the tablet. This enables fast as well as prolonged release of PES over 6-8 h. Because the sugar coating technologies are troublesome and rarely used nowadays, the aim of this study was to develop alternative oral dosage forms containing L (5 mg) and PES (120 mg). It was assumed that, similarly to the original product, the total dose of L and the half dose of PES should be released during 1 h and the remaining dose of PES ought to be gradually released for up to 8 h.

Cutaneous absorption and elimination of three acyclic terpenes—in vitro studies

The purpose of the study was to investigete skin absorption and elimination of three acyclic terpenes: citronellol (C), linalool (L) and linalyl acetate (LA). The pure terpenes were applied onto the human skin in vitro, and after 1-4 h, their content in the stratum corneum layers and in the epidermis/dermis was determined using gas chromatography. Similarly, the amounts of terpenes in the skin were analysed during 4 h following 1-h absorption. Good absorption to the all skin layers was demonstrated as soon as after 1 h: the total skin cumulation of L, LA and C was 827, 124 and 954 microg/cm2, respectively. A self-promoting absorption was observed for L, since the amount of this terpene analysed in the stratum corneum after 1 h was 78.3, rising to 479 microg/cm2 after 4 h. During the elimination phase, a constant drop in the total amount in the skin was observed only for C, while the total skin content of L and LA did not change, although diffusion from the stratum corneum to epidermis/dermis occurred. The log P values of the terpenes were calculated using three different programs, but generally, neither absorption nor elimination can be directly correlated with the physicochemical parameters, despite of the fact that the least absorption was observed for the most lipophilic LA.

In vitro studies on penetration of terpenes from matrix-type transdermal systems through human skin

Polyurethane matrices containing up to 39% of the terpenes eucalyptol, L-limonene, D-limonene, dipentene or terpinolene were produced. Release of the terpenes directly to the acceptor fluid, as well as through isolated human epidermis and dermis, was studied. In the presence of dermis the penetration profiles were very similar to the release profiles, indicating that dermis does not present a barrier for penetration of terpenes. For all terpenes the penetration was slower in the presence of epidermis (K(p) was in the range 0.21-1.8x10(-3) cm/h). Release and penetration through the epidermis and dermis were fastest for dipenetene (mixture of D-limonene and L-limonene), being at least 3-4 times faster than for D-limonene and L-limonene. Large amounts of terpenes found in epidermis (approximately 1.5 mg/cm(2)) indicate that affinity of these compounds to the stratum corneum is very high.

Effect of penetration enhancers on isosorbide dinitrate penetration through rat skin from a transdermal therapeutic system

Percutaneous absorption of isosorbide dinitrate (ISDN) from a transdermal therapeutic system (TTS) with or without penetration enhancers was studied. The concentration of ISDN and its metabolites, isosorbide-5-mononitrate (IS-5-MN) and isosorbide-2-mononitrate (IS-2-MN), was determined in rat plasma during a 48 h application of TTS. The increased skin-penetration enhancing effect of oleic acid and propylene glycol in comparison to polyethylene glycol 400 and isopropyl myristate on percutaneous permeation of ISDN was shown. It was expressed by higher values of C(max) and AUC. After the application of TTS, a lower ISDN and molar ratio of its metabolites was observed than after oral administration.