The enhancing effect of a triethanolamine-ethanol-isopropyl myristate mixed system on the skin permeation of acidic drugs

An explanation for the difference in the percutaneous penetration behavior of tamsulosin induced by two different O-acylmenthol derivatives

Using tamsulosin (TAL) as a model drug, the aim of this study was to investigate and compare the percutaneous permeation behavior of two menthol derivatives, 2-isopropyl-5-methylcyclohexyl heptanoate (M-HEP) and 2-isopropyl-5-methylcyclohexyl decanoate (M-DEC). In vitro transdermal permeation study was carried out using porcine skin. The residual amount of enhancers in the skin after permeation experiment was determined by gas chromatographic (GC) method. The penetration depths of fluorescein were visualized by two-photon confocal laser scanning microscopy (2P-LSM) after the skin being treated with different enhancers. Furthermore, changes in the stretching frequency of functional group of ceramide were investigated by using attenuated total reflectance Fourier transform infrared (ATR-FTIR) technique. After M-HEP addition, the cumulative amount of TAL permeated in 8 h (Q8) reached 20.57±0.54 μg/cm2 and the depth of fluorescein was 40 μm; the CH2 of ceramide symmetric stretching frequency was 4 cm−1 blue shifted. However, M-DEC has an opposite effect on TAL permeation compared with that of M-HEP. TAL is a crucial factor affecting permeation procedure, and microenvironment of lipid region determines promotion capability of the enhancers.

Correlation between rheological properties, in vitro release, and percutaneous permeation of tetrahydropalmatine

The aim of the present work was to investigate the influence of formulation factors including different grades of Carbopol® matrices and penetration enhancers on the percutaneous permeation of tetrahydropalmatine (THP), rheological properties, and in vitro release; and the correlation behind rheological properties, in vitro release, and percutaneous permeation. Transdermal penetration of THP through excised rabbit skin and in vitro release of THP across transparent Cellophane® were performed by vertical Franz diffusion cell. Rheological analyses were proceeded in terms of "steady flow tests", "oscillation stress sweep", and "creep recovery". The result of percutaneous penetration of THP indicated that, the emulgel prepared with Carbopol® 971P (Cp 971P) as the matrix and N-methyl-2-pyrrolidone (NMP) as the penetration enhancer had the highest cumulative permeation amount (118.19 μg/cm(2)). All the experimental data showed a good fit to the Casson model in viscosimetric studies no matter what the types of matrices or the kinds of penetration enhancers were. The release profile fitted the zero-order release kinetics model with Cp 971P as the matrix without any penetration enhancers. However, when adding penetration enhancers, in vitro release of THP presented anomalous (non-Fickian) release kinetics. Clarifying the relationship behind percutaneous permeation of THP, rheological properties, and in vitro release will provide us with profound insights and facilitate the design of specific emulgel.

Effect of O-acylmenthol and salt formation on the skin permeation of diclofenac acid

PURPOSE

To enhance the transdermal delivery of diclofenac acid (DA) by using O-acylmenthol as a penetration enhancer and complexing with amines, or by a combination of the two methods.

METHODS

The skin permeability of diclofenac was tested in vitro across rat skin with each of the evaluated permeants in a saturated isopropyl myristate (IPM) donor solution.

RESULTS

A 4.5-fold increase in the flux of diclofenac was observed by ion-pair formation with diethylamine; however, the cations with hydroxyl groups had negative effects on the transdermal delivery of diclofenac. 2-isopropyl-5-methylcyclohexyl 2-hydroxypanoate and 2-isopropyl-5-methylcyclohexyl heptanoate produced significant increase in the permeation of diclofenac potassium (D-K); however, both of them were ineffective for the other diclofenac salts, including diclofenac diethylamine (D-DETA), diclofenac ethanolamine (D-EA), diclofenac diethanolamine (D-DEA), diclofenac triethanolamine, and diclofenac N-(hydroxylethyl) piperidine. 2-isopropyl-5-methylcyclohexyl tetradecanoate was effective on the penetration of D-K, D-DETA, D-EA, and D-DEA. Also, it is exciting to note that the combined use of diethylamine with 2-isopropyl-5-methylcyclohexyl tetradecanoate produced a 9.74-fold increase in accumulation amount of diclofenac compared with DA in IPM.

CONCLUSIONS

The use of ion pair in combination with O-acylmenthol is necessary to further increase the diclofenac flux to provide better compliance for the patients undergoing clinical therapy.

Effect of ion-pairing and enhancers on scutellarin skin permeability

The aim of this work was to investigate the effect of enhancers and organic amines on the in-vitro percutaneous absorption of the major pharmacologically active compound, scutellarin, obtained from breviscapine extract. The donor vehicle consisted of isopropyl myristate-ethanol in a ratio of 4:1. Percutaneous absorption across full thickness rat skin was investigated in-vitro using 2-chamber diffusion cells, with reverse-phase HPLC for quantification of the permeating scutellarin. Organic amines increased scutellarin permeation by ion-pair formation. We also found that the cumulative amount of scutellarin over a period of 12 h of scutellarin was inversely related to the molecular weight of organic amines (r = 0.9134), as well as the logarithm of scutellarin permeability coefficient inversely related to the partition coefficient of organic amines (r = 0.8929). All the permeation enhancers tested increased the cumulative amount of scutellarin over a period of 12 h, and the order of this increase was n-methyl-2-pyrrolidone, oleic acid, menthol or Azone. Drug solubility in donor phase was markedly increased by Azone and n-methyl-2-pyrrolidone, and reduced by menthol and oleic acid. The combined effects of ethanolamine plus Azone, ethanolamine plus menthol, and Azone plus menthol were also investigated. Azone plus menthol had a synergistic effect on the cumulative amount of scutellarin over a period of 12 h.

Enhancement of transdermal drug delivery via synergistic action of chemicals

Transdermal drug delivery is an attractive alternative to conventional techniques for administration of systemic therapeutics. One challenge in designing transdermal drug delivery systems is to overcome the natural transport barrier of the skin. Chemicals offer tremendous potential in overcoming the skin barrier to enhance transport of drug molecules. Individual chemicals are however limited in their efficacy in disrupting the skin barrier at low concentrations and usually cause skin irritation at high concentrations. Multicomponent mixtures of chemicals, however, have been shown to provide high skin permeabilization potency as compared to individual chemicals without necessarily causing irritation. Here we review systems employing synergistic mixtures of chemicals that offer superior skin permeation enhancement. These synergistic systems include solvent mixtures, microemulsions, eutectic mixtures, complex self-assembled vesicles and inclusion complexes. Methods for design and discovery of such synergistic systems are also discussed.

The enhancing effect of ion-pairing on the skin permeation of glipizide

The purpose of the present study was to investigate the permeation of glipizide (GP) and observe the effect of an interaction with amines as counter ions, including diethylamine, triethylamine, ethanolamine, diethanolamine, triethanolamine, N-(2-hydroxylethyl) piperidine. Permeation experiments were performed in vitro, using rat abdominal skin as a barrier. The lipophilic donor system consisting of isopropyl myristate (IPM) and ethanol (EtOH; EI system, 8:2) produced a marked enhancement of GP flux through rat skin. All the amines investigated in this study had performed an enhancing effect on GP flux, and triethylamine had the most potent enhancing effect on GP in the vehicle IPM:EtOH = 8:2(w/w). In the presence of counter ions, the solubility of GP in the donor solution (IPM:EtOH = 8:2) was increased and the log K (o/w) of GP was decreased, which may due to higher solubility of the GP in the IPM:EtOH = 8:2(w/w). (13)C NMR spectroscopy was used to identify the ion-pairing formation between GP and the respective counter ion. It was surprising that all the four enhancers examined, such as isopropyl myristate, propylene glycol, N-methyl-2-pyrrolidone, azone, and oleic acid, had no enhancing effect on the percutaneous permeation of GP. This study showed that the formation of ion-pairs between GP and counter ions is a useful method to promote the skin permeation of GP.

Effect of permeation enhancers and organic acids on the skin permeation of indapamide

The aim of present study was to investigate the transdermal properties of indapamide and to explore the efficacy of various permeation enhancers and organic acids with regard to the percutaneous absorption of indapamide. Permeation experiments were performed in vitro, using rat abdominal skin as a barrier. In the permeation studies, 2-chamber diffusion cells were used. The results obtained indicate that N-dodecylazepan-2-one, N-methyl-2-pyrrolidone, menthol and oleic acid had a strong enhancing effect on the permeation of indapamide and N-dodecylazepan-2-one exhibited the most potent enhancing effect. All eight of the organic acids chosen had a potent enhancing effect on the permeation of indapamide across rat abdominal skin. Among the organic acids examined, lactic acid had the greatest enhancing effect. The formation of an ion-pair between indapamide and organic acids may be responsible for the enhanced skin permeation of indapamide. Although the exact reason remains unknown, it is worth carrying out further investigations.

Physicochemical and crystallographic characterization of mefenamic acid complexes with alkanolamines

The preparation of mefenamic acid (MH)-alkanolamine (propanolamine, diethanolamine, triethanolamine) complexes was attempted to increase the transdermal flux of MH. Differential scanning calorimetry, Fourier transform infrared spectroscopy, and X-ray crystallographic studies demonstrated that MH and each alkanolamine formed an ion pair complex. The series of amine complexes had a lower melting point and higher solubility in water compared with pure MH.

The use of complexation with alkanolamines to facilitate skin permeation of mefenamic acid

The preparation of mefenamic acid (MH)-alkanolamine [monoethanolamine, diethanolamine, triethanolamine and propanolamine] complexes was attempted to increase the transdermal flux of MH. A lipophilic enhancer system consisting of isopropyl myristate (IPM) and ethanol (9:1; EI system) produced a marked enhancement of MH flux from the alkanolamine complexes through hairless rat skin membrane. Among the alkanolamines examined, the propanolamine complex had the greatest enhancing effect on the permeation of MH. The observed permeation enhancement of MH-alkanolamine complexes by the EI system was explained by an analysis based on a two-layer diffusion model. The stratum corneum immersed in IPM forms a continuous phase of vehicle and stratum corneum and, from the phase, ethanol transport the MH-alkanolamine complexes to the epidermis and dermis, and the complexes, which are more water soluble than MH, exhibit increased partition into the epidermis and dermis, as the flux increases.