Penetration enhancement by menthol combined with a solubilization effect in a mixed solvent system

Film-Forming Sprays for Topical Drug Delivery

Film-forming sprays offer many advantages compared to conventional topical preparations because they can provide uniform drug distribution and dose, increased bioavailability, lower incidence of irritation, continuous drug release, and accelerated wound healing through moisture control. Film-forming sprays consist of polymers and excipients that improve the characteristics of preparations and enhance the stability of active substances. Each type of polymer and excipient will produce films with different features. Therefore, the various types of polymers and excipients and their evaluation standards need to be examined for the development of a more optimal form of film-forming spray. The selected literature included research on polymers as film-forming matrices and the application of these sprays for medical purposes or for potential medical use. This article discusses the types and concentrations of polymers and excipients, sprayer types, evaluations, and critical parameters in determining the sprayability and film characteristics. The review concludes that both natural and synthetic polymers that have in situ film or viscoelastic properties can be used to optimise topical drug delivery.

Comparison of normal versus imiquimod-induced psoriatic skin in mice for penetration of drugs and nanoparticles

Background

As an immune-mediated skin disease, psoriasis encounters therapeutic challenges on topical drug development due to the unclear mechanism, and complicated morphological and physiological changes in the skin.

Methods

In this study, imiquimod-induced psoriatic mouse skin (IMQ-psoriatic skin) was chosen as the in vitro pathological model to explore the penetration behaviors of drugs and nanoparticles (NPs).

Results

Compared with normal skin, significantly higher penetration and skin accumulation were observed in IMQ-psoriatic skin for all the three model drugs. When poorly water-soluble curcumin was formulated as NPs that were subsequently loaded in gel, the drug’s penetration and accumulation in both normal and IMQ-psoriatic skins were significantly improved, in comparison with that of the curcumin suspension. Interestingly, the NPs’ size effect, in terms of their penetration and accumulation behaviors, was more pronounced for IMQ-psoriatic skin. Furthermore, by taking three sized FluoSpheres^® as model NPs, confocal laser scanning microscopy demonstrated that the penetration pathways of NPs no longer followed the hair follicles channels, instead they were more widely distributed in the IMQ-psoriatic skin.

Conclusion

In conclusion, the alternation of the IMQ-psoriatic skin structure will lead to the enhanced penetration of drug and NPs, and should be considered in topical drug formulation and further clinical practice for psoriasis therapy.

A comparison of transdermal over-the-counter lidocaine 3.6% menthol 1.25%, Rx lidocaine 5% and placebo for back pain and arthritis

Aim: Transdermal lidocaine therapy has become a gold standard as part of a treatment regimen for patients who suffer from localized pain. We compared transdermal patches: over-the-counter (OTC) lidocaine 3.6% combined with menthol 1.25%, prescription lidocaine 5% (Rx) and placebo. Methods: In a double-blind, placebo-controlled trial, 87 patients were randomized to: OTC, Rx or placebo. Results: OTC met primary end points of noninferiority compared with Rx for efficacy, side effects and quality of life. Versus placebo, OTC proved superiority for efficacy, general activity and normal work. Side effects were similar. Conclusion: It is theorized that menthol's ability to increase skin permeability facilitated more efficient drug delivery to the site of pain causing higher than expected efficacy. Decreased cost and resource utilization could benefit patients and payers.

Formulation and evaluation of clotrimazole transdermal spray

CONTEXT

Transdermal spray (TS) of clotrimazole (CTZ) was formulated to improve the drug transport through the skin up to 12 h to achieve the antifungal efficacy.

OBJECTIVE

The aim of present study was to formulate and evaluate antifungal transdermal spray to improve the permeation of clotrimazole across the skin and to decrease the dosing frequency in fungal infection.

MATERIALS AND METHODS

Different ratios of ethanol and acetone and various grades of eudragit and ethyl cellulose were evaluated according to six criteria: viscosity, drying time, stickiness, appearance and integrity on skin and water washability. Propylene glycol (PG) and polyethylene glycol 400 (PEG 400) were used in the study as plasticizer and solubilizer. The TS was evaluated for in vitro drug release, spray angle, spray pattern, average weight per dose, pH, drug content, evaporation time, leak test and antifungal efficacy study.

RESULTS AND DISCUSSION

Eudragit E100 and blend of ethanol and acetone (80:20) satisfied the desired criteria. The selection of optimized batch was based on the results of in vitro drug release, spray pattern and spray angle. The optimized batch showed the spray angle <85° and uniform spray pattern. The formulation containing PG showed higher drug release than PEG 400. The inclusion of eutectic mixture consisting of camphor and menthol (1:1) showed improved drug transport through the rat skin and larger mean zone of inhibition indicating the improved antifungal efficacy.

CONCLUSION

The TS of CTZ can be an innovative and promising approach for the topical administration in the fungal diseases.

Disintegration mediated controlled release supersaturating solid dispersion formulation of an insoluble drug: design, development, optimization, and in vitro evaluation

The objective of this study was to develop a solid dispersion based controlled release system for drug substances that are poorly soluble in water. A wax-based disintegration mediated controlled release system was designed based on the fact that an amorphous drug can crystallize out from hydrophilic matrices. For this study, cilostazol (CIL) was selected as the model drug, as it exhibits poor aqueous solubility. An amorphous solid dispersion was prepared to assist the drug to attain a supersaturated state. Povidone was used as carrier for solid dispersion (spray drying technique), hydrogenated vegetable oil (HVO) as wax matrix former, and sodium carboxymethyl cellulose (NaCMC) as a disintegrant. The extreme vertices mixture design (EVMD) was applied to optimize the designed and developed composition. The optimized formulation provided a dissolution pattern which was equivalent to the predicted curve, ascertaining that the optimal formulation could be accomplished with EVMD. The release profile of CIL was described by the Higuchi's model better than zero-order, first-order, and Hixson-Crowell's model, which indicated that the supersaturation state of CIL dominated to allow drug release by diffusion rather than disintegration regulated release as is generally observed by Hixson-Crowell's model. The optimized composition was evaluated for disintegration, dissolution, XRD, and stability studies. It was found that the amorphous state as well as the dissolution profile of CIL was maintained under the accelerated conditions of 40°C/75% RH for 6 months.

Menthol: a simple monoterpene with remarkable biological properties

Menthol is a cyclic monoterpene alcohol which possesses well-known cooling characteristics and a residual minty smell of the oil remnants from which it was obtained. Because of these attributes it is one of the most important flavouring additives besides vanilla and citrus. Due to this reason it is used in a variety of consumer products ranging from confections such as chocolate and chewing gum to oral-care products such as toothpaste as well as in over-the-counter medicinal products for its cooling and biological effects. Its cooling effects are not exclusive to medicinal use. Approximately one quarter of the cigarettes on the market contain menthol and small amounts of menthol are even included in non-mentholated cigarettes. Natural menthol is isolated exclusively from Mentha canadensis, but can also be synthesised on industrial scale through various processes. Although menthol exists in eight stereoisomeric forms, (-)-menthol from the natural source and synthesised menthol with the same structure is the most preferred isomer. The demand for menthol is high and it was previously estimated that the worldwide use of menthol was 30-32,000 metric tonnes per annum. Menthol is not a predominant compound of the essential oils as it can only be found as a constituent of a limited number of aromatic plants. These plants are known to exhibit biological activity in vitro and in vivo such as antibacterial, antifungal, antipruritic, anticancer and analgesic effects, and are also an effective fumigant. In addition, menthol is one of the most effective terpenes used to enhance the dermal penetration of pharmaceuticals. This review summarises the chemical and biological properties of menthol and highlights its cooling effects and toxicity.

Isotretinoin oil-based capsule formulation optimization

The purpose of this study was to develop and optimize an isotretinoin oil-based capsule with specific dissolution pattern. A three-factor-constrained mixture design was used to prepare the systemic model formulations. The independent factors were the components of oil-based capsule including beeswax (X₁), hydrogenated coconut oil (X₂), and soybean oil (X₃). The drug release percentages at 10, 30, 60, and 90 min were selected as responses. The effect of formulation factors including that on responses was inspected by using response surface methodology (RSM). Multiple-response optimization was performed to search for the appropriate formulation with specific release pattern. It was found that the interaction effect of these formulation factors (X₁X₂, X₁X₃, and X₂X₃) showed more potential influence than that of the main factors (X₁, X₂, and X₃). An optimal predicted formulation with Y_10 min, Y_30 min, Y_60 min, and Y_90 min release values of 12.3%, 36.7%, 73.6%, and 92.7% at X₁, X₂, and X₃ of 5.75, 15.37, and 78.88, respectively, was developed. The new formulation was prepared and performed by the dissolution test. The similarity factor f₂ was 54.8, indicating that the dissolution pattern of the new optimized formulation showed equivalence to the predicted profile.

Enhancement of gene transfer efficiency in the Bcap-37 cell line by dimethyl sulphoxide and menthol

Simple and efficient gene transfer into the nucleus would facilitate non-viral gene delivery. One promising method of non-viral gene delivery is to apply penetration enhancers. Chemicals, such as dimethyl sulfoxide (DMSO) and menthol, may have promise as non-toxic vehicles in improving gene transfer efficiency. In this study, the cytotoxic effects of DMSO and menthol were evaluated using MTT assays. Gene delivery efficiency in a human breast cancer cell line (Bcap-37) was investigated by quantitative PCR, fluorescence microscopy and flow cytometry. Non-toxic concentrations of DMSO (2%) and menthol (12.5 µM) enhanced the efficiency of liposome-mediated gene delivery in Bcap-37 cells. Quantitative PCR results showed that growth hormone (GH) mRNA expression in the post-menthol and pre-DMSO treatment groups was 10-fold higher compared to that in the liposome group, while in the pre-menthol and post-DMSO treatment groups, a 30-fold increase in GH mRNA expression was observed. Both DMSO and menthol treatments increased green fluorescent protein (GFP) expression efficiency as shown by fluorescence microscopy experiments. Compared to the liposome group, the number of positive cells in the pre-menthol and post-DMSO treatment groups was significantly increased by 15%. Furthermore, cell cycle analysis demonstrated that there were significant differences among the DMSO-treated group, the menthol-treated group and the normal group, which implied different effects of DMSO and menthol treatments. In conclusion, both non-toxic and harmless DMSO (2%) and menthol (12.5 µM) treatments improve gene transfer efficiency, while post-DMSO treatment may be the most effective protocol in increasing transgene expression efficiency.

Effect of menthol on ocular drug delivery

BACKGROUND

To assess how safe and effective it is to use menthol as a permeability enhancer in ophthalmic drug delivery systems.

METHODS

In this study, the effect of menthol on permeability of dexamethasone disodium phosphate in the cornea and sclera was investigated in vitro. Application of topical drops and subconjunctival injection of dexamethasone disodium phosphate with or without 0.1% menthol was administered to rabbit eyes, and the drug concentration was detected in aqueous humor, cornea, vitreous, and retinochoroidal tissues. The safety of menthol was assessed on the basis of corneal hydration level, Draize test, electroretinography (ERG), and histological examination.

RESULTS

0.05% and 0.1% menthol significantly enhanced the penetration of dexamethasone in the cornea, but did not change the dexamethasone penetration in sclera in vitro. When topical drops of dexamethasone containing 0.1% menthol were administered, a significantly increased concentration of dexamethasone in the cornea and aqueous humor tissues was reported, but dexamethasone concentrations remained unaffected in the retina-choroid tissues. On the other hand, increased drug concentration in aqueous humor, cornea, vitreous and retinochoroidal tissues was achieved through subconjunctival injection. No signs of irritation were observed when menthol was administered at concentrations ranging from 0.025%-0.1%; moreover, no substantial toxic reactions were observed in corneal hydration level, electrophysiological, or histological examinations after the addition of 0.1% menthol.

CONCLUSIONS

Menthol may improve the ocular penetration of a drug in a transcorneal and transscleral drug delivery system without causing toxic reactions.

Efficacy study of vesicular gel containing methotrexate and menthol combination on parakeratotic rat skin model

Methotrexate (MTX) is indicated in the symptomatic control of severe, recalcitrant, and disabling psoriasis. The oral or parenteral route of administration causes systemic toxicity. The topical route of delivery, though, reduces systemic toxicity and has limited applicability due to restricted permeability. Liposomal and niosomal MTX topical formulations have also been investigated with limited success to achieve drug localization in the skin. Menthol has been suggested in conditions of psoriasis, in addition to its skin-penetration-enhancing effect on drugs. The present work aimed at investigating the potential benefits of combining menthol with MTX in a vesicular gel base for not only improving the penetration and dermal availability of MTX, but also to render such a formulation more effective with greater patient acceptability. MTX liposomes were prepared by thin-film hydration, and the vesicles were characterized for drug-entrapment efficiency, size, and morphology. These liposomal vesicles were incorporated in a gel base, and this vesicular gel was evaluated for transdermal drug permeation and extent of drug accumulation in the skin, using a rat skin ex vivo model. Skin histology studies were carried out to investigate any structural changes caused by the permeation enhancers. Antipsoriatic efficacy of the formulations was tested in vivo, using the rat tail model. The results indicated that the vesicular gel containing menthol could cause maximum drug retention in the skin. The skin treated with menthol had a disrupted epidermis and microcavities. The in vivo studies also ascertained the effectiveness of the formulation in inducing a normal pattern of differentiation in the rat tail skin that initially showed parakeratosis, which is also characteristic of psoriatic epidermis. These results show the potential of vesicular gel containing MTX and menthol to improve penetration into the skin and cause drug retention in skin appendages.

Fabrication of modified transport fluconazole transdermal spray containing ethyl cellulose and Eudragit RS100 as film formers

The present investigation was undertaken to fabricate modified transport fluconazole transdermal spray using ethyl cellulose and Eudragit RS100 as film-forming polymers. Eudragit RS100 (X(1)) and ethyl cellulose (X(2)) were selected as independent variables in 3(2) full factorial design, whereas drug transport in first hour (Y (1)) and the time required for 50% drug transport (Y(2)) were selected as dependent variables. Eutectic blend of camphor and menthol was used as permeation enhancer cum solvent for film-forming polymers. The pH, viscosity, volume of solution delivered upon each actuation, spray angle, ex-in vivo physical evaluation and in vitro drug transport of the formulated products were evaluated. The optimized batch B16 containing 5.25% w/w ethyl cellulose and 10.6% w/w Eudragit RS100 was formulated by overlapping the contour plots of Y(1) and Y(2). The pH, viscosity, volume of solution sprayed upon each actuation and spray angle of the batch B16 was 6.3, 52.9 cPs, 0.24 ml and 82.6 degrees respectively. The film of optimized batch was flexible and dermal-adhesive. The responses Y(1) and Y(2) of batch B16 were 7.91 microg/ml and 347 min respectively. The kinetics of drug transport was best explained by the Korsmeyer and Peppas model. The eutectic mixture consisting of equal parts of camphor and menthol showed improved drug permeation through shed snake skin. Short-term stability study demonstrated insignificant changes in performance characteristics.

Interdisciplinary, translational, and community-based participatory research: finding a common language to improve cancer research

Preventing cancer, downstaging disease at diagnosis, and reducing mortality require that relevant research findings be translated across scientific disciplines and into clinical and public health practice. Interdisciplinary research focuses on using the languages of different scientific disciplines to share techniques and philosophical perspectives to enhance discovery and development of innovations; (i.e., from the "left end" of the research continuum). Community-based participatory research (CBPR), whose relevance often is relegated to the "right end" (i.e., delivery and dissemination) of the research continuum, represents an important means for understanding how many cancers are caused as well as for ensuring that basic science research findings affect cancer outcomes in materially important ways. Effective interdisciplinary research and CBPR both require an ability to communicate effectively across groups that often start out neither understanding each other's worldviews nor even speaking the same language. Both demand an ability and willingness to treat individuals from other communities with respect and understanding. We describe the similarities between CBPR and both translational and interdisciplinary research, and then illustrate our points using squamous cell carcinoma of the esophagus as an example of how to deepen understanding and increase relevance by applying techniques of CBPR and interdisciplinary engagement.

Formulation and Evaluation of Limonene-Based Membrane-Moderated Transdermal Therapeutic System of Nimodipine

The aim of the present study was to design a membrane-moderated transdermal therapeutic system (TTS) of nimodipine using 2% w/w hydroxypropyl methylcellulose (HPMC) gel as a reservoir system containing 4% w/w of limonene as a penetration enhancer. The permeability flux of nimodipine through ethylene vinyl acetate (EVA) copolymer membrane was found to increase with an increase in vinyl acetate content in the copolymer (9 to 28%). The effect of pressure-sensitive adhesives such as TACKITE A 4MED on the permeability of nimodipine through EVA membrane 2825 (28% w/w vinyl acetate) or membrane/rat skin composite also was studied. The permeability flux of nimodipine from the chosen EVA 2825 (with 28% vinyl acetate content) was 159.72 +/- 1.96 microg/cm2/hr, and this flux further decreased to 141.85 +/- 1.54 microg/cm2/hr on application of pressure-sensitive adhesive (TACKWHITE A 4MED). However, the transdermal permeability flux of nimodipine across EVA 2825 membrane coated with TACKWHITE A 4MED/rat skin composite was found to be 126.59 +/- 2.72 microg/cm2/hr, which is 1.3-fold greater than the required flux. Thus, a new transdermal therapeutic system for nimodipine was formulated using EVA 2825 membrane coated with a pressure-sensitive adhesive TACKWHITE 4A MED and 2% w/w HPMC gel as reservoir containing 4% w/w of limonene as a penetration enhancer. The bioavailability studies in healthy human volunteers indicated that the TTS of nimodipine, designed in the present study, provided steady-state plasma concentration of the drug with minimal fluctuations for 20 hr with improved bioavailability in comparison with the immediate release tablet dosage form.

Evaluation of ketoprofen formulations via penetration rate and irritation in vivo study

The purpose of the present study was to design an optimal ketoprofen gel with appropriate penetration rate, shortened lag time and acceptable skin irritation. The combination of different mechanism enhancers including nonivamide, menthol and ethanol were used as multi-enhancers for producing a synergistic enhancement effect and reducing the skin irritation via diminishing the used amount of enhancers. The central composite design was applied to prepare a systemic formulation. The penetration rate (PR), lag time (LT) and skin irritation score (TIS) of a commercial product (Formax plus gel containing 3% ketoprofen) were determined by in vivo study and used as a criterion for designed formulations. The PR, LT and TIS of commercial product were 462.2+/-162.5 microg/h, 0.6+/-0.1 h and 12.7+/-0.6, respectively. Among these designed experimental formulations, four formulations including F07 (code: -1/+1/-1), F11 (code: +1/+1/-1), F13 (code: 0/0/-1.732) and F14 (code: 0/+1.732/0), their PR was not smaller and LT and TIS were not greater than that of commercial product, indicating that these experimental ketoprofen gels could be used in the clinical situation.

Bioavailability of nerodilol-based transdermal therapeutic system of nicorandil in human volunteers

The objective of the present investigation was to design and evaluate a nerodilol-based transdermal therapeutic system (TTS) for finding its ability in providing the desired steady-state plasma concentration of nicorandil in human volunteers. The influence of EVA2825 membrane, adhesive-coated EVA2825 membrane and adhesive-coated EVA2825-rat skin composite on the in vitro permeation of nicorandil from a nerodilol-based HPMC gel drug reservoir was studied against a control (excised rat skin alone). The flux of nicorandil from the nerodilol-based HMPC drug reservoir across excised rat skin (control) was 384.0+/-4.6 microg/cm2 h and this decreased to 222.7+/-7.1 microg/cm2 h when studied across EVA2825 membrane indicating that EVA2825 membrane was effective as rate controlling membrane. The flux of the drug decreased to 183.8+/-5.7 microg/cm2 h on application of a water-based acrylic adhesive (TACKWHITE A 4MED) coat to EVA2825 membrane. However, the flux of nicorandil across adhesive-coated EVA2825-membrane-rat-skin composite was 164.8+/-1.8 microg/cm2 h, which was 1.74-times of the required flux that prompted for preparation of TTS. The nerodilol-based drug reservoir system was sandwiched between a composite of adhesive-coated EVA2825 membrane-release liner and a backing membrane. The resultant sandwich was heat-sealed to produce circle-shaped TTS (20 cm2) that were subjected to bioavailability study in human volunteers against immediate release nicorandil tablet. The nerodilol-based TTS provided a steady-state plasma concentration of 25.5 ng/ml for 24 h in human volunteers. It was concluded that the nerodilol-based TTS of nicorandil provided the desired plasma concentration of the drug for the predetermined period of time with minimal fluctuations.

Optimization of pH-independent release of nicardipine hydrochloride extended-release matrix tablets using response surface methodology

The purpose of this study was to optimize the pH-dependent release of nicardipine hydrochloride extended release formulations by using simultaneously combination two hydrophilic polymers: hydroxypropylmethylcellulose (HPMC) and sodium alginate as retardant and avicel as additive. The constrained mixture experimental design was used to prepare systematic model formulations which were composed of three formulation variables: the content of HPMC (X1), avicel (X2), and sodium alginate (X3). The response surface methodology (RSM) and multiple response optimization utilizing the polynomial equation were used to search for the optimal formulation with specific release rate at different time intervals and to quantify the effect of each formulation variables. The drug release percent at 3, 6 and 12 h were the target responses and were restricted to 10-30% (Y3h), 40-65% (Y6h) and not less than 80% (Y12h), respectively. The results showed that the effect of combination of HPMC and sodium alginate was the most influence factor on the drug release from extended-release matrix tablets. The observed results of Y3h, Y6h and Y12h coincided well with the predictions in the RSM optimization technique, indicating it was quite useful for optimizing pharmaceutical formulation. The mechanism of drug release from extended-release matrix tablets was dependent on the added amount of alginate. The release kinetic of drug from HPMC matrix tablets with alginate was followed the zero-order release pattern.

Transdermal self-permeation enhancement of ibuprofen

The objective of this study was to prepare saturated solutions of ibuprofen, of different concentrations, and to investigate their effect on permeation of ibuprofen across rat epidermis. Ibuprofen saturated solutions were prepared using 0.1, 0.2, 0.3 and 0.4 M disodium hydrogen phosphate solution (DHP). The solubility of ibuprofen in DHP increased as the molarity of DHP increased. Thus the four saturated solutions of ibuprofen (0.1M-DHP-IBU, 0.2M-DHP-IBU, 0.3M-DHP-IBU and 0.4M-DHP-IBU) have different concentrations of the same drug, and showed same pH (pH 7.0+/-1). The permeability study was also carried out using human epidermis and silastic membrane. Permeation rate of ibuprofen across rat epidermis and human epidermis from 0.4M-DHP-IBU was much greater than from 0.1M-DHP-IBU. The magnitudes of increase in the drug flux were 46.4-fold with rat epidermis and 9.4-fold with human epidermis. Such a great increase in drug flux was not observed with silastic membrane, only 1.4-fold. This suggests that the increased drug flux is likely due to drug-skin interaction and not the increased concentration of ibuprofen per se. Surface tension (ST) measurements of DHP versus ibuprofen concentration showed ST reduction of DHP, from 72 to 27.9 dyn/cm. This is an indication that ibuprofen acted as ionic surfactant and the observed skin permeability enhancement is attributed to disruption of stratum corneum barrier. Results of DSC study supported this assumption. DSC of untreated rat stratum corneum samples showed lipid transitions at 41.9+/-0.0 degrees C (T1), 55.1+/-1.6 degrees C (T(x)), 70.2+/-0.1 degrees C (T2) and 77.5+/-0.1 degrees C (T3), while those pretreated with 0.4M-DHP-IBU did not show the first three lipid transitions. Also, pretreatment of rat epidermis with 0.4M-DHP-IBU enhanced permeation of diclofenac sodium greater than 1250-fold. This corroborates that ibuprofen not only enhances its own permeation but also that of other drugs, such as diclofenac sodium.

Once-daily propranolol extended-release tablet dosage form: formulation design and in vitro/in vivo investigation

The purpose of this study was to develop and optimize the propranolol once-daily extended release formulations containing HPMC, Microcrystalline cellulose (MCC) and lactose. In vitro studies, the response surface methodology and multiple response optimization utilizing the polynomial equation were used to search for the optimal formulation with specific release rate at different time intervals. The constrained mixture experimental design was used to prepare systematic model formulations, which were composed of three formulation variables: the content of HPMC (X(1)) MCC (X(2)) and lactose (X(3)). The drug release percent at 1.5, 4, 8, 14 and 24 h were the target responses and were restricted to 15-30, 35-55, 55-75, 75-90 and 90-110%, respectively. The results showed that the optimized formulation provided a dissolution pattern equivalent to the predicted curve, which indicated that the optimal formulation could be obtained using response surface methodology. The mechanism of drug release from HMPC matrix tablets followed non-Fickian diffusion. In the vivo study, the MRT was prolonged for matrix tablets when compared with commercial immediate release tablets. Furthermore, a linear relationship between in vitro dissolution and in vivo absorption was observed in the beagle dogs.

Formulation of an HPMC Gel Drug Reservoir System with Ethanol-Water as a Solvent System and Limonene as a Penetration Enhancer for Enhancing in vitro Transdermal Delivery of Nicorandil

The objective of the present study was to formulate a hydroxypropyl methylcellulose (HPMC) gel drug reservoir system with ethanol-water as a solvent system and limonene as a penetration enhancer for enhancing the transdermal delivery of nicorandil so as to develop and fabricate a membrane-moderated transdermal therapeutic system (TTS). The in vitro permeation of nicorandil was determined across rat abdominal skin from a solvent system consisting of ethanol or various proportions of ethanol and water. The ethanol-water (70:30 v/v) solvent system that provided an optimal transdermal permeation was used in formulating an HPMC gel drug reservoir system with selected concentrations (0% w/w, 4% w/w, 6% w/w, 8% w/w or 10% w/w) of limonene as a penetration enhancer for further enhancement of transdermal permeation of nicorandil. The amount of nicorandil permeated in 24 h was found increased with an increase in the concentration of limonene in the drug reservoir system up to a concentration of 6% w/w, but beyond this concentration there was no further increase in the amount of drug permeated. The flux of nicorandil was 370.9 +/- 4.2 microg/cm2 x h from the drug reservoir system with 6% w/w of limonene, which is about 2.6 times the required flux to be obtained across rat abdominal skin for producing the desired plasma concentration for the predetermined period in humans. The results of a Fourier Transform Infrared study indicated that limonene enhanced the percutaneous permeation of nicorandil by partially extracting the stratum corneum lipids. It is concluded that the HPMC gel drug reservoir system prepared with a 70:30 v/v ethanol-water solvent system containing 6% w/w of limonene is useful in designing and fabricating a membrane-moderated TTS of nicorandil.

Enhancement Effect ofp‐Menthane‐3,8‐diol on In Vitro Permeation of Antipyrine and Indomethacin Through Yucatan Micropig Skin

The enhancing effect of p-Menthane-3,8-diol (MDO) on skin permeation of antipyrine (ANP) and indomethacin (IM) through Yucatan micropig skin in vitro was compared with 1-menthol. p-Menthane-3,8-diol is a metabolite of 1-menthol and has little odor. It is easy to combine the vehicle because of lower lipophilicity than 1-menthol. All formulations contained 40% (v/v) ethanol. The permeation of ANP increased with MDO about three times that without enhancer by increasing ANP concentration in the skin. However, the MDO effect was about a quarter that of 1-menthol. The permeation of IM with MDO was about 15 times that with no enhancer and it was almost the same as that with 1-menthol. The lag time of permeation was not significantly changed by MDO, which was not so in the case of 1-menthol. Skin concentration of IM increased about 11 times and six times with MDO and 1-menthol, respectively. MDO and 1-menthol partitioned to the skin relatively high concentrations, 5.9 and 2.5 mg/ cm3, respectively. The solubility of IM in the skin was improved by MDO, and consequently, the permeation of IM was enhanced.

Penetration‐Enhancing Effect of Ethanol–Water Solvent System and Ethanolic Solution of Carvone on Transdermal Permeability of Nimodipine from HPMC Gel Across Rat Abdominal Skin

The aim of this investigation was to find the effect of the ethanol-water solvent system and the ethanolic solution of carvone on the permeation of nimodipine across rat abdominal skin in order to select a suitable solvent system and optimal concentration of carvone for the development of membrane-moderated transdermal therapeutic system of nimodipine. The solubility of nimodipine in water, ethanol, and ethanol-water cosolvent systems, or the selected concentration of carvone [2% (w/w) to 12% (w/w)] in 60:40 (v/v) ethanol-water were determined. The effect of these solvents or cosolvent systems on the transdermal permeation of nimodipine was also studied using in vitro permeability studies across the rat abdominal skin. The co-solvent system containing 60:40 (v/v) of ethanol-water showed highest permeability across the rat abdominal skin. Further, the effect of ethanolic solution [60% (v/v) ethanol-water] of carvone [2% (w/w) to 12% (w/w)] on the in vitro permeation of nimodipine across the rat abdominal skin from 2% (w/w) hydroxypropyl methylcellulose (HPMC) gel was also investigated. The transdermal permeability of nimodipine across rat abdominal skin was enhanced further by the addition of carvone to HPMC gel prepared with 60% (v/v) of ethanol. There was a steady effect on the flux of nimodipine (161.02 +/- 4.14 microg/cm2/hr) with an enhancement ratio of 4.56 when carvone was incorporated at a concentration of 10% (w/w) in HPMC gels prepared with 60% (v/v) ethanol. The Fourier transform infrared data indicated that ethanolic solution of carvone increased the transdermal permeability of nimodipine across the rat abdominal skin by partial extraction of lipids in the stratum corneum. The results suggest that 10% (w/w) of carvone in 60% (v/v) ethanol-water, along with HPMC as antinucleating agent may be useful for enhancing the skin permeability of nimodipine from the membrane-moderated transdermal therapeutic system.

Influence of menthol and pressure-sensitive adhesives on the in vivo performance of membrane-moderated transdermal therapeutic system of nicardipine hydrochloride in human volunteers

A membrane-moderated transdermal therapeutic system of nicardipine hydrochloride was developed using 2% w/w hydroxypropylcellulose (HPC) gel as a reservoir system containing 5% w/w of menthol as a penetration enhancer. The permeability flux of nicardipine hydrochloride through the ethylene vinyl acetate (EVA) copolymer membrane was found to increase with an increase in vinyl acetate content in the copolymer. The effect of various pressure-sensitive adhesives (MA-31, MA-38 or TACKWHITE A 4MED on the permeability of nicardipine hydrochloride through EVA 2825 membrane (28% w/w vinyl acetate) or EVA 2825 membrane/skin composite was also studied. The results showed that nicardipine hydrochloride permeability through EVA 2825 membrane coated with TACKWHITE A 4MED/skin composite was higher than that coated with MA-31 or MA-38. Thus, a new transdermal therapeutic system for nicardipine hydrochloride was formulated using EVA 2825 membrane coated with a pressure-sensitive adhesive TACKWHITE A 4MED, and 2% w/w HPC gel as reservoir containing 5% w/w of menthol as a penetration enhancer. In vivo studies in healthy human volunteers indicated that the TTS of nicardipine hydrochloride, designed in the present study, provided steady-state plasma concentration of the drug with minimal fluctuations for 26h with improved bioavailability in comparison with the immediate release capsule dosage form.

Penetration enhancing effect of menthol on the percutaneous flux of nicardipine hydrochloride through excised rat epidermis from hydroxypropyl cellulose gels

The aim of the present investigation is to study the penetration enhancing effect of menthol on the percutaneous flux of nicardipine hydrochloride through the excised rat epidermis from 2% w/w hydroxypropyl cellulose (HPC) gel system. The HPC gel formulations containing nicardipine hydrochloride and selected concentrations of menthol (0-12% w/w) were prepared, and evaluated for in vitro permeation of the drug through excised rat abdominal epidermis. The percutaneous flux of nicardipine hydrochloride across rat epidermis was enhanced markedly by the addition of menthol to the HPC gels. A maximum flux of nicardipine hydrochloride (227.70 +/- 1.30 micrograms cm-2 hr-1) was observed with an enhancement ratio of 7.12 when menthol was incorporated at a concentration of 8% w/w in a reservoir HPC system. The differential scanning calorimetry and Fourier transform-infrared spectroscopy data indicated that menthol increased the percutaneous flux of nicardipine hydrochloride through the rat skin by partial extraction of lipids in the stratum corneum. The results suggest that menthol may be useful for increasing the skin permeability of nicardipine hydrochloride from transdermal therapeutic system containing HPC gel as a reservoir.

Enhanced percutaneous permeability of nicardipine hydrochloride by carvone across the rat abdominal skin

The purpose of this study was to investigate the effect of carvone on the permeation of nicardipine hydrochloride across the excised rat abdominal epidermis from 2% w/w hydroxypropyl cellulose (HPC) gel system. The HPC gel formulations containing nicardipine hydrochloride (1% w/w) and selected concentrations of carvone (0 to 12% w/w) were prepared, and evaluated for drug content, stability of the drug, and in vitro permeation of the drug through excised rat abdominal epidermis. The HPC gel was found to contain 99.98 to 101.6% of nicardipine hydrochloride, and the drug was found to be stable in the HPC gels. The permeation flux of nicardipine hydrochloride across rat epidermis was increased markedly by the addition of carvone to the HPC gels. A maximum flux of nicardipine hydrochloride (243.95.70 +/- 1.90 microg/cm2/hr) was observed with an enhancement ratio of 7.9 when carvone was incorporated at a concentration of 12% w/w in the HPC reservoir system. The differential scanning calorimetry and Fourier transform-infrared data indicated that carvone increased the permeability of nicardipine hydrochloride across the rat epidermis by partial extraction of lipids in the stratum corneum. The results suggest that carvone may be useful for enhancing the skin permeability of nicardipine hydrochloride from transdermal therapeutic system containing HPC gel as a reservoir.

Evaluation of Percutaneous Absorption of Midazolam by Terpenes

Midazolam is a highly lipophilic drug that is widely used in preanesthetic medication. Recently, terpenes have been reported to show an enhancing effect on percutaneous absorption of drugs. The effect of terpenes (l-menthol, d-limonene, RS-(+/-)-beta-citronellol, geraniol) on the in vitro percutaneous absorption of midazolam through rat skin was evaluated using unjacketed Franz diffusion cells. Since midazolam is a lipophilic drug, percutaneous penetration is low and a percutaneous penetration enhancer is necessary for its percutaneous absorption. The terpenes (5%, w/v) in combination with 30% ethanol, and 20% propylene glycol significantly increased the percutaneous absorption of midazolam in comparison to the control. In vitro data suggested that d-limonene is the most effective enhancer among terpenes and other penetration enhancers such as Azone. In in vivo percutaneous absorption assays, the midazolam formulation using d-limonene could penetrate through rat skin, but the other terpenes could not penetrate. In conclusion, d-limonene in combination with ethanol can be used to enhance the percutaneous absorption of the highly lipophilic drug midazolam.

Influence of limonene on the bioavailability of nicardipine hydrochloride from membrane-moderated transdermal therapeutic systems in human volunteers

The aim of the present study was to develop a membrane-moderated transdermal therapeutic system (TTS) of nicardipine hydrochloride using 2%w/w hydroxy propyl cellulose (HPC) gel as a reservoir system containing 4%w/w of limonene as a penetration enhancer. The permeability flux of nicardipine hydrochloride through ethylene vinyl acetate (EVA) copolymer membrane was found to increase with an increase in vinyl acetate (VA) content in the copolymer. The effect of various pressure-sensitive adhesives (MA-31, MA-38 or TACKWHITE A 4MED) on the permeability of nicardipine hydrochloride through EVA membrane 2825 (28% w/w VA) or membrane/skin composite was also studied. The results showed that nicardipine hydrochloride permeability through EVA 2825 membrane coated with TACKWHITE 4A MED/skin composite was higher than that coated with MA-31or MA-38. Thus a new TTS for nicardipine hydrochloride was formulated using EVA 2825 membrane coated with a pressure-sensitive adhesive TACKWHITE 4A MED and 2%w/w HPC gel as reservoir containing 4%w/w of limonene as a penetration enhancer. The bioavailability studies in healthy human volunteers indicated that the TTS of nicardipine hydrochloride, designed in the present study, provided steady state plasma concentration of the drug with minimal fluctuations for 20 h with improved bioavailability in comparison with the immediate release capsule dosage form.

Terpenes in propylene glycol as skin-penetration enhancers: permeation and partition of haloperidol, Fourier transform infrared spectroscopy, and differential scanning calorimetry

The respective alcoholic terpenes carvacrol, linalool, and alpha-terpineol were used at 5% w/v in propylene glycol (PG) to increase the in vitro permeation of haloperidol (HP) through human skin. The possible enhancement mechanism was then elucidated with HP-stratum corneum (SC) binding studies, Fourier transform infrared spectroscopy, and differential scanning calorimetry. The greatest increase in the permeation of HP was achieved with linalool followed by carvacrol and terpineol. HP permeation with linalool was predicted to reach a therapeutic plasma concentration and therapeutic daily-permeated amounts. Carvacrol increased lag time, which was attributed to slow redistribution of the enhancer within SC. Carvacrol increased the partition of the drug to the pulverized SC. Pure PG extracted lipids from SC but less than that achieved by the terpenes in PG. Terpenes extracted lipids to a similar extent. An increase in bilayer cohesion in the remaining lipids present in the SC could be attributed to the alignment of terpenes within the lipid bilayer. The higher permeation with linalool was attributed to its molecular orientation within the lipid bilayer. Terpenes showed different rates of SC dehydration but did not change the percentages of secondary structures of keratin.