Essential Oils from Sweet Basil (Ocimum basilicum) as Novel Enhancers to Accelerate Transdermal Drug Delivery

Current Development of Chemical Penetration Enhancers for Transdermal Insulin Delivery

The use of the transdermal delivery system has recently gained ample recognition due to the ability to deliver drug molecules across the skin membrane, serving as an alternative to conventional oral or injectable routes. Subcutaneous insulin injection is the mainstay treatment for diabetes mellitus which often leads to non-compliance among patients, especially in younger patients. Apart from its invasiveness, the long-term consequences of insulin injection cause the development of physical trauma, which includes lipohypertrophy at the site of administration, scarring, infection, and sometimes nerve damage. Hence, there is a quest for a better alternative to drug delivery that is non-invasive and easily adaptable. One of the potential solutions is the transdermal delivery method. However, the stratum corneum (the top layer of skin) is the greatest barrier in transporting large molecules like insulin. Therefore, various chemical enhancers have been proposed to promote stratum corneum permeability, or they are designed to increase the permeability of the full epidermis, such as the use of ionic liquid, peptides, chemical pre-treatment as well as packaging insulin with carriers or nanoparticles. In this review, the recent progress in the development of chemical enhancers for transdermal insulin delivery is discussed along with the possible mechanistic of action and the potential outlook on the proposed permeation approaches in comparison to other therapeutical drugs

Natural essential oils: A promising strategy for treating cardio-cerebrovascular diseases

ETHNOPHARMACOLOGICAL RELEVANCE

Essential oils (EO) are volatile compounds obtained from different parts of natural plants, and have been used in national, traditional and folk medicine to treat various health problems all over the world. Records indicate that in history, herbal medicines rich in EO have been widely used for the treatment of CVDs in many countries, such as China.

AIM OF THE STUDY

This review focused on the traditional application and modern pharmacological mechanisms of herbal medicine EO against CVDs in preclinical and clinical trials through multi-targets synergy. Besides, the EO and anti-CVDs drugs were compared, and the broad application of EO was explained from the properties of drugs and aromatic administration routes.

MATERIALS AND METHODS

Information about EO and CVDs was collected from electronic databases such as Web of Science, ScienceDirect, PubMed, and China National Knowledge Infrastructure (CNKI). The obtained data sets were sequentially arranged for better understanding of EO' potential.

RESULTS

The study showed that EO had significant application in CVDs at different countries or regions since ancient times. Aiming at the complex pathological mechanisms of CVDs, including intracellular calcium overload, oxidative stress, inflammation, vascular endothelial cell injury and dysfunction and dyslipidemia, we summarized the roles of EO on CVDs in preclinical and clinical through multi-targets intervention. Besides, EO had the dual properties of drug and excipients. And aromatherapy was one of the complementary therapies to improve CVDs.

CONCLUSIONS

This paper reviewed the EO on traditional treatment, preclinical mechanism and clinical application of CVDs. As important sources of traditional medicines, EO' remarkable efficacy had been confirmed in comprehensive literature reports, which showed that EO had great medicinal potential.

Therapeutic benefits of natural oils along with permeation enhancing activity

The skin is the largest organ of the integumentary system with a multifunctional purpose to protect the body from heat and microbes, regulate body temperature, and act as a sensory organ. A topical dosage form applied on the skin will have to cross the stratum corneum, which would then allow the dosage form to traverse the subsequent layers of the skin. The drug with poor solubility and short half-life would serve as an ideal candidate for its delivery via the transdermal route. This review reports the role of natural oils in enhancing the permeation of drugs through skin as they possess different features like natural origin, favorable penetration enhancement, and partitioning action in the skin. Chemical penetration enhancers have been used widely but are associated with toxicities. Thus, more research should be channelized in the area of extraction of oils from natural sources, along with their active constituents, which can serve as therapeutic alternatives to various disorders and diseases. Natural oils are obtained from leaves, fruits, flowers, seeds, bark, and roots, which have a therapeutic potential as well as penetration enhancing activity. The demerits of oral drug delivery include degradation of drugs in the gastrointestinal tract, addition of taste masking, and coating of tablets, which can be overcome by delivering the drug via the transdermal route. Natural oil contains lipids, flavonoids, and terpenes, which play a significant role in anti-inflammatory and penetration enhancing activity.

Lignans Isolated From Flower Buds of Magnolia fargesii Attenuate Airway Inflammation Induced by Cigarette Smoke in vitro and in vivo

The flower buds of Magnolia fargesii, known traditionally as Xinyi, exert anti-inflammatory effects against inflammatory lung diseases such as COPD. Lignans isolated from Xinyi are an important group of plant-derived anti-inflammatory compounds. However, the mechanisms of action underlying their protective effects against COPD are not yet fully understood. Here, we showed that seven lignans (lignans 1–7) obtained from a CHCl₃ fraction of Xinyi effectively suppress the inflammatory response in CSC-stimulated airway epithelial cells (in vitro) and in a mouse model of COPD established by exposure to CS and LPS. The CHCl₃ fraction was found to inhibit CSC-induced IL-6 expression in human airway epithelial cells and to suppress the infiltration of inflammatory cells (neutrophils and macrophages) and secretion of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the mouse model. Similarly, each of the seven lignans isolated from the CHCl₃ fraction also suppressed the infiltration of inflammatory cells (neutrophils and macrophages) and secretion of inflammatory mediators such as reactive oxygen species (ROS), TNF-α, and IL-6 in vivo. Notably, all lignan compounds significantly suppressed both extracellular signal-related kinase (ERK) and Akt phosphorylation levels in CSC-stimulated human lung mucoepidermoid carcinoma (NCI-H292) cells. Of these, lignan 1 (dimethylpinoresinol) inhibited the expression of CSC-induced inflammatory cytokines (IL-1β, -6, and -8) in vitro in a dose-dependent manner by suppressing the activation of epidermal growth factor receptor (EGFR) and its downstream effectors, including ERK and Akt, in NCI-H292 cells. Our results show that the lignans isolated from Xinyi may prevent airway inflammatory diseases through the suppression of EGFR and its downstream effectors.

The potential effects of Ocimum basilicum on health: a review of pharmacological and toxicological studies

INTRODUCTION

Basil (Ocimum basilicum L., OB) is a plant world widely used as a spice and a typical ingredient of the healthy Mediterranean diet. In traditional medicine, OB is indicated for many maladies and conditions; OB-containing nutritional supplements are increasingly sold. Conversely, safety concerns have been raised about the promutagens and procarcinogens alkenylbenzenes contained in OB. Areas covered: A critical review of the current status of OB as a nutraceutical, the pharmacology of its bioactive components, the rationale for its indications, and its safety. Expert opinion: Due to the polyphenolic and flavonoidic content, OB can be considered as an important ingredient in healthy diets; OB preparations may be effective as chemopreventive agents or adjunctive therapy in the treatment of different clinical conditions. From a toxicological perspective, since the tumorigenic potential of alkenylbenzenes is counteracted by other OB constituents such as nevadensin, it can be concluded that OB consumption in food and preparations is safe. The only concern relates to OB essential oils: in this case, a concentration limit for alkenylbenzenes should be precautionary defined, and the use of plant chemotypes with no or low levels of these alkylbenzenes for the preparation of essential oils should be made compulsory.

Anti-inflammatory and antiedematogenic activity of the Ocimum basilicum essential oil and its main compound estragole: In vivo mouse models

The genus Ocimum are used in cooking, however, their essential oils are utilized in traditional medicine as aromatherapy. The present study was carried out to investigate the chemical composition and systemic anti-inflammatory activity of the Ocimum basilicum essential oil (EOOB) and its major component estragole, as well as its possible mechanisms of action. The Ocimum basilicum essential oil was obtained by hydrodistillation and analyzed by GC-MS. The anti-inflammatory action was verified using acute and chronic in vivo tests as paw edema, peritonitis, and vascular permeability and granulomatous inflammation model. The anti-inflammatory mechanism of action was analyzed by the participation of histamine and arachidonic acid pathways. The chemical profile analysis identified fourteen components present in the essential oil, within them: estragole (60.96%). The in vivo test results show that treatment with EOOB (100 and 50 mg/kg) and estragole (60 and 30 mg/kg) significantly reduced paw edema induced by carrageenan and dextran. The smallest doses of EOOB (50 mg/kg) and estragole (30 mg/kg) showed efficacy in the reduction of paw edema induced by histamine and arachidonic acid, vascular permeability inhibition and leukocyte emigration in the peritoneal fluid. Theses doses were capable of reducing the chronic inflammatory process. The results observed between the EOOB and estragole demonstrate efficacy in anti-inflammatory activity, however, the essential oil is more efficacious in the acute and chronic anti-inflammatory action. This study confirms the therapeutic potential of this plant and reinforces the validity of its use in popular medicine.

Transdermal absorption enhancing effect of the essential oil of Rosmarinus officinalis on percutaneous absorption of Na diclofenac from topical gel

CONTEXT

Rosemary essential oil has been used topically for several purposes (analgesic, anti acne, and anti-inflammatory) in Iranian traditional medicine.

OBJECTIVES

This investigation aimed to study the effect of essential oil of Rosmarinus officinalis L. (Lamiaceae) on the transdermal absorption of Na diclofenac from topical gel.

MATERIAL AND METHODS

Diclofenac sodium topical gel was prepared with HPMC K4M and Carbopol 934P as a gelling agent, and several vehicles. The most stable gel was chosen and enhancing effects of the essential oil with different concentrations (0.1, 0.5, and 1.0% w/w) on the permeation of diclofenac were evaluated. The anti-nociceptive effect of preparations was evaluated based on the formalin and tail flick tests in mice.

RESULTS

The major constituents of the essential oil were 1,8-cineol (15.96%), α-pinene (13.38%), camphor (7.87%), bornyl acetate (6.54%), verbenone (5.82%), borneol (5.23%), camphene (4.96%), and (E)-caryophyllene (3.8%). Topical diclofenac containing 0.5% essential oil showed more analgesic effect after 25, 30, and 35 min (p < 0.001) than the reference drug in the tail flick test. The analgesic effect of preparation containing 1% essential oil was more than reference gel after 15 min (p < 0.05). This difference was observed after 20, 25, 30, 35, and 40 min (p < 0.001) too. Rosemary essential oil 1% promoted analgesic effect of drug in comparison with diclofenac gel in the formalin early phase (p < 0.05). The enhancing effect of rosemary was observed in 0.5 and 1% concentration (p < 0.05 and p < 0.001, respectively) in the late phase.

CONCLUSION

This study proved the enhancing effect of 0.5 and 1% of rosemary essential oil on diclofenac percutaneous absorption.

Enhancement effect of essential oils from the fruits and leaves of Alpinia oxyphylla on skin permeation and deposition of indomethacin

Essential oils from plants are gaining increasing attention as potential chemical penetration enhancers.

Essential oils and their constituents as skin penetration enhancer for transdermal drug delivery: a review

OBJECTIVES

In this paper, we focused on essential oils and their constituents as skin penetration enhancers for transdermal drug delivery, mechanism of their action as well as their possible toxicity.

KEY FINDINGS

Essential oils and their volatile constituents can penetrate through the skin as well as enhance penetration of different drug from topical formulation into the lower skin layers using different mechanisms of action based on (1) disintegration of the highly ordered intercellular lipid structure between corneocytes in stratum corneum, (2) interaction with intercellular domain of protein, which induces their conformational modification, (3) increase the partitioning of a drug. After application to the skin, essential oils and their components are rapidly metabolized, not accumulated in the organism and fast excreted what strongly suggest that they can be successfully use as safe penetration enhancers.

SUMMARY

Essential oils and their constituents may be preferred over the traditionally used synthetics materials as safe and suitable permeation enhancers to promote the percutaneous absorption of hydrophilic and lipophilic drugs from topical formulation into the lower skin layers.

Modulation of the pharmacokinetics, therapeutic and adverse effects of NSAIDs by Chinese herbal medicines

INTRODUCTION

Concomitant use of NSAIDs and Chinese herbal medicines (CHMs) is frequent, yet summarized information on their interactions is lacking.

AREAS COVERED

A systematic review of literature in four evidence-based English databases was performed. Articles which reported CHMs altering the pharmacokinetics, therapeutic and adverse effects of NSAIDs were identified and summarized. Such interactions may lead to beneficial, detrimental or no change in outcomes. The current review covers four therapeutic effects of NSAIDs, including: i) anti-inflammatory; ii) analgesic; iii) antiplatelet, cardiovascular and cerebrovascular; and iv) anticancer effects and four adverse effects of NSAIDs, including: i) gastrointestinal ulcer; ii) nephrotoxicity; iii) hepatotoxicity; and iv) antiplatelet effects and bleeding.

EXPERT OPINION

While majority of CHMs demonstrated effectiveness in alleviating NSAIDs-induced adverse effects and potentiating the therapeutic effects, this review provides insights for development of CHMs as add-on medications to NSAIDs therapies. However, since limited information was from well-designed clinical trials, the findings are not yet conclusive and more clinical studies are warranted to provide guidance for healthcare professionals. In future, researches on interactions between NSAIDs and CHMs are expected to grow and modern approaches such as pharmacogenomics might enhance the throughput and accuracy of identifying clinically relevant interactions.

Lemon (Citrus limon, Burm.f.) essential oil enhances the trans-epidermal release of lipid-(A, E) and water-(B6, C) soluble vitamins from topical emulsions in reconstructed human epidermis

Topical bioavailability of lipid- and water-soluble vitamins is a critical issue for protecting or anti-ageing formulations. Using 17-day-old SkinEthic(®) reconstructed human epidermis, we investigated (at 34°C) the role of lemon EO in enhancing the penetration of α-tocopherol (E) and retinyl acetate (A), pyridoxine (B(6)) and ascorbic acid (C), released from O/W or W/O emulsions. D-limonene, α-pinene and p-cymene (65.9, 2.2 and 0.5%w/w of the oil) had skin permeability coefficients Ps (10(-3) cm h(-1)) of 0.56 ± 0.03 (or 0.73 ± 0.02), 0.72 ± 0.05 (or 0.98 ± 0.05) and 0.84 ± 0.04 (or 1.14 ± 0.04), respectively, when incorporated in a W/O (or O/W) emulsion. Vitamins B6, C and A had Ps values of (3.0 ± 0.4) × 10(-3), (7.9 ± 0.6) × 10(-3) and (0.37 ± 0.02) × 10(-5) cm h(-1), respectively, and their flux through the skin was enhanced by a factor of 4.1, 3.4 and 5.8, respectively, in the presence of lemon EO. The penetration of vitamin E was nine-fold enhanced. Lemon EO produced only reversible modification of TEWL, and it is a safe and effective penetration enhancer for topical administration of lipid- and water-soluble vitamins.

Transdermal Drug Delivery Enhancement by Compounds of Natural Origin

The transdermal route of administration offers an alternative pathway for systemic drug delivery with numerous advantages over conventional routes. Regrettably, the stratum corneum forms a formidable barrier that hinders the percutaneous penetration of most drugs, offering an important protection mechanism to the organism against entrance of possible dangerous exogenous molecules. Different types of penetration enhancers have shown the potential to reversibly overcome this barrier to provide effective delivery of drugs across the skin. Although certain chemical and physical skin penetration enhancers are already employed by the pharmaceutical industry in commercially available transdermal products, some skin penetration enhancers are associated with irritating and toxic effects. This emphasizes the need for the discovery of new, safe and effective skin penetration enhancers. Penetration enhancers from natural origin have become popular as they offer several benefits over their synthetic counterparts such as sustainable mass production from a renewable resource and lower cost depending on the type of extraction used. The aim of this article is to give a comprehensive summary of the results from scientific research conducted on skin penetration enhancers of natural origin. The discussions on these natural penetration enhancers have been organized into the following chemical classes: essential oils, terpenes, fatty acids and polysaccharides.

Niaouli oils from different sources: analysis and influence on cutaneous permeation of estradiol in vitro

Previous studies in vitro had identified niaouli essential oil (NEO) as a valuable transdermal permeation promoter for estradiol (ES). Subsequent considerations on the complex issue of NEO provenance and composition stimulated the present investigation, which was aimed at defining the composition of NEOs obtained from four different sources, at evaluating their influence on transdermal permeation of ES through hairless mouse skin, and at formulating and evaluating simpler terpene mixtures mimicking the NEOs' composition. While all oils contained 1,8-cineol (eucalyptol) as the main component, appreciable variations in composition could be evidenced, originating differences on the ES cutaneous permeation. Two artificial mixtures containing the same proportions of the main terpenes present in each oil (except the commercially unavailable gamma-terpineol) proved equal or significantly superior in activity when compared with the original oils. It is felt that this study might contribute to the formulation of terpene mixtures acting more efficiently and reproducibly with respect to natural NEOs, whose complex and variable composition, depending on growing place, season, and extraction process, is well documented in the relevant literature.

Effects of chemical enhancers on human epidermal membrane: Structure-enhancement relationship based on maximum enhancement (E(max))

Chemical penetration enhancers are widely used in transdermal pharmaceuticals as well as cosmetic products. Selection of suitable enhancers in topical formulations requires an understanding of the mechanism of action of these enhancers. The objective of the present study was to evaluate the enhancement effects of a number of commonly known enhancers and cosmetic ingredients on permeation across human epidermal membrane (HEM). The potencies of these chemical enhancers-maximum enhancement, E(max)-were compared at their highest thermodynamic activity in equilibrium with HEM (i.e., solubility equilibrium). This was achieved by the treatment of HEM with the enhancer or phosphate buffered saline (PBS) saturated with the enhancer. Passive transport experiments were then conducted with a model permeant corticosterone to determine the effects of these enhancers on the lipoidal pathway of HEM. The results suggest that E(max) of an enhancer is related to its octanol/water partition coefficient and its solubility in the HEM lipid domain. A relationship between enhancer E(max) and its solubility in silicone elastomer was also observed, suggesting the use of silicone solubility to predict enhancer potency. Based on the E(max) results, some common topical ingredients were found to be more potent enhancers than a number of well-known chemical enhancers.

Antimicrobial efficacy of chlorhexidine digluconate alone and in combination with eucalyptus oil, tea tree oil and thymol against planktonic and biofilm cultures of Staphylococcus epidermidis

OBJECTIVES

Effective skin antisepsis and disinfection of medical devices are key factors in preventing many healthcare-acquired infections associated with skin microorganisms, particularly Staphylococcus epidermidis. The aim of this study was to investigate the antimicrobial efficacy of chlorhexidine digluconate (CHG), a widely used antiseptic in clinical practice, alone and in combination with tea tree oil (TTO), eucalyptus oil (EO) and thymol against planktonic and biofilm cultures of S. epidermidis.

METHODS

Antimicrobial susceptibility assays against S. epidermidis in a suspension and in a biofilm mode of growth were performed with broth microdilution and ATP bioluminescence methods, respectively. Synergy of antimicrobial agents was evaluated with the chequerboard method.

RESULTS

CHG exhibited antimicrobial activity against S. epidermidis in both suspension and biofilm (MIC 2-8 mg/L). Of the essential oils thymol exhibited the greatest antimicrobial efficacy (0.5-4 g/L) against S. epidermidis in suspension and biofilm followed by TTO (2-16 g/L) and EO (4-64 g/L). MICs of CHG and EO were reduced against S. epidermidis biofilm when in combination (MIC of 8 reduced to 0.25-1 mg/L and MIC of 32-64 reduced to 4 g/L for CHG and EO, respectively). Furthermore, the combination of EO with CHG demonstrated synergistic activity against S. epidermidis biofilm with a fractional inhibitory concentration index of <0.5.

CONCLUSIONS

The results from this study suggest that there may be a role for essential oils, in particular EO, for improved skin antisepsis when combined with CHG.

The effect of clove oil on the transdermal delivery of ibuprofen in the rabbit by in vitro and in vivo methods

The study was designed to evaluate skin permeation enhancement effect of essential oils from Eugenia caryophyllata (clove oil) in rabbits and to compare the in vitro absorption and in vivo permeation using ibuprofen as a model drug. The in vitro results indicated a significant permeation enhancement effect of the clove oil. The group with 1% oil appeared to the flux (239 microg/cm(2)/hr), and 3% oil was 293 microg/cm(2)/hr to some extent similar with 2% azone group (327 microg/cm(2)/hr). The enhancement ratio of clove oil was 7.3. In vivo results also demonstrated that clove oil showed a significant permeation enhancement effect, but the enhancement of clove oil was relatively weak than in vitro. The group with 3% oil exhibited the higher value of area under the curve (AUC) of 80.8 microg/mL.hr, which was 2.4 times the high of control. The AUC value of 3% oil group was similar to that of 2% azone group (89.8 mug/mL.hr). The GC-MS results indicated eugenol and acetyleugenol identified from clove oil might mainly contribute to enhance in vitro and in vivo absorption of ibuprofen because of its large quantities (90.93%).

Percutaneous penetration kinetics of lidocaine and prilocaine in two local anesthetic formulations assessed by in vivo microdialysis in pigs

The aim of this study was to characterize and compare the percutaneous penetration kinetics of lidocaine (L) and prilocaine (P) in two local anesthetic formulations by in vivo microdialysis coupled with HPLC. The microdialysis system for studying lidocaine and prilocaine was calibrated by a no-net-flux method in vitro and retrodialysis method in vivo, respectively. A dosage of 0.2 g/cm2 of an in-house P-L formulation (2.5% lidocaine and 2.5% prilocaine, methylcellulose-based) and commercially available Eutectic Mixture of Local Anesthesia (EMLA, 2.5% lidocaine and 2.5% prilocaine, carbopol-based) was separately but symmetrically applied in the dorsal region of pigs. Saline (0.9%, w/v) was perfused into the linear microdialysis probe at a flow rate of 1.5 microl/min. Dialysate was collected upon topical application up to 6 h at 20-min intervals and assessed by HPLC. The results demonstrated the area under the concentration-time curve (AUC(0-6 h)) of lidocaine and prilocaine in EMLA was 71.95+/-23.36 microg h/ml and 38.01+/-14.8 microg h/ml, respectively, in comparison to 167.11+/-56.12 microg h/ml and 87.02+/-30.38 microg h/ml in the P-L formulation. The maximal concentrations (Cmax) of lidocaine and prilocaine in the dermis were 29.2+/-9.08 microg/ml and 16.54+/-5.31 microg/ml in EMLA and 80.93+/-17.98 microg/ml and 43.69+/-12.87 microg/ml in the P-L formulation, respectively. This study indicates a well-calibrated microdialysis system can provide vital real-time information on percutaneous drug delivery and specifically a methylcellulose-based P-L formulation can increase percutaneous absorption of both lidocaine and prilocaine in pigs compared to carbopol-based EMLA.

Pharmaceutical and therapeutic Potentials of essential oils and their individual volatile constituents: a review

Essential oils and their volatile constituents are used widely to prevent and treat human disease. The possible role and mode of action of these natural products is discussed with regard to the prevention and treatment of cancer, cardiovascular diseases including atherosclerosis and thrombosis, as well as their bioactivity as antibacterial, antiviral, antioxidants and antidiabetic agents. Their application as natural skin penetration enhancers for transdermal drug delivery and the therapeutic properties of essential oils in aroma and massage therapy will also be outlined.

Natural Oils Affect the Human Skin Integrity and the Percutaneous Penetration of Benzoic Acid Dose-Dependently

Natural oils are extensively used in cosmetics and as treatment for a growing number of more or less specific ailments. Skin irritation and cases of allergy have repeatedly been described in the literature following exposure to these oils. The present study evaluated the extent to which three natural oils (eucalyptus oil, tea tree oil, peppermint oil) would affect the skin integrity and the percutaneous penetration of benzoic acid when applied topically in relevant concentrations. An experimental in vitro model using static diffusion cells mounted with human breast or abdominal skin was applied. The three natural oils decreased the skin integrity dose-dependently. Concomitant dermal exposure to low concentrations of peppermint oil reduced the percutaneous penetration of benzoic acid. The present study lends support to the notion that low concentrations of peppermint oil may act protective against percutaneous penetration of some chemicals, whereas higher concentrations may decrease the integrity of the dermal barrier.

Overcoming the Stratum Corneum: The Modulation of Skin Penetration

It is preferred that topically administered drugs act either dermally or transdermally. For that reason they have to penetrate into the deeper skin layers or permeate the skin. The outermost layer of the human skin, the stratum corneum, is responsible for its barrier function. Most topically administered drugs do not have the ability to penetrate the stratum corneum. In these cases modulations of the skin penetration profiles of these drugs and skin barrier manipulations are necessary. A skin penetration enhancement can be achieved either chemically, physically or by use of appropriate formulations. Numerous chemical compounds have been evaluated for penetration-enhancing activity, and different modes of action have been identified for skin penetration enhancement. In addition to chemical methods, skin penetration of drugs can be improved by physical options such as iontophoresis and phonophoresis, as well as by combinations of both chemical and physical methods or by combinations of several physical methods. There are cases where skin penetration of the drug used in the formulation is not the aim of the topical administration. Penetration reducers can be used to prevent chemicals entering the systemic circulation. This article concentrates on the progress made mainly over the last decade by use of chemical penetration enhancers. The different action modes of these substances are explained, including the basic principles of the physical skin penetration enhancement techniques and examples for their application.

In Vivo and in Vitro Evaluation of Essential Oils from Ligusticum chuanxiong HORT on the Transdermal Delivery of Flurbiprofen in Rabbits

The present study was designed to evaluate skin permeation enhancement effect of essential oils from Ligusticum chuanxiong Hort (chuanxiong oil) in rabbits and to compare the in vivo absorption and in vitro permeation using flurbiprofen as a model drug. In vivo results demonstrated that chuanxiong oil showed a rapid and marked permeation enhancement effect. The group with 10% oil exhibited the highest value of area under the curve (AUC) of 418+/-124 microg/ml x h, which was 2.43 times the high of control. The AUC value of 3% oil group (245+/-81.6 microg/ml x h) was similar to that of 5% oleic acid group (235+/-74.5 microg/ml x h). Whereas in vitro results indicated the enhancement of chuanxiong oil was relatively weak. The group with 3% oil appeared to the highest flurbiprofen flux (84.9+/-19.3 microg/cm2/h), to some extent lower than 5% oleic acid group (107+/-5.85 microg/cm2/h). At 10% and 15% concentrations, chuanxiong oil even decreased the flux of flurbiprofen compared with the control. Both in vitro results with pretreated skin and flurbiprofen content accumulated in skin indicated the potential mechanism for the in vitro enhancement of chuanxiong oil was the weakened barrier function by improving in the partitioning of flurbiprofen to the stratum corneum. The discrepancy was noted between the in vivo and in vitro results, indicating only about the weakened barrier function was not enough to explain the sharply increment of in vivo absorption of flurbiprofen by chuanxiong oil. The GS-MS results indicated phthalides identified from chuanxiong oil might mainly contribute to enhance in vivo absorption of flurbiprofen because of its large quantities (91.15%).