Effect Of Azone Research Articles

Time dependence of the enhancement effect of chemical enhancers: Molecular mechanisms of enhancing kinetics

Chemical enhancers are widely used for facilitating drug penetration in transdermal drug delivery system (TDDS). However, there is a lack of knowledge about how the enhancement effect changes over time. In this study, on the basis of kinetic parameters of enhancement effect, molecular details of the dynamic enhancement process was described and a new hypothesis of the recovery mechanism of the skin barrier function was proposed. Using pretreated skin and flurbiprofen patch, the effects of Azone (AZ) and menthyl decanoate (MT-10) were evaluated with in vitro permeation experiment and further confirmed by confocal laser scanning microscopy (CLSM) and TEWL. The results showed that the enhancement ratio (ER) increased firstly, then reached a plateau and finally decreased. The enhancement effect of MT-10 was slower (Tonset, MT-10>Tonset, AZ), weaker (ERmax, MT-10<ERmax, AZ) and shorter (Teff, MT-10<Teff, AZ) than that of AZ. According to the results of CLSM, ATR-FTIR and molecular dynamic simulation, the dynamic enhancement effect was caused by the variation of the diffusion coefficient of intercellular lipid in the stratum corneum (SC), which was dependent on the affinity between enhancers and lipid. Moreover, the skin barrier function recovered although a large amount of enhancers still existed in the SC. Additionally, according to the results of ATR-FTIR, molecular docking and skin retention study, the dynamic effect of AZ on the skin protein only induced skin irritation but showed no influence on drug penetration, so did the amount of the enhancer. In conclusion, dynamic enhancement effect was caused by the dynamic effect of the enhancer on the SC intercellular lipid, and the skin barrier function recovered by accepting the enhancer as a new component of the lipid bilayer.

Effect of azone on intraocular permeability of basic fibroblast growth factor

Background Many researches confirmed that basic fibroblast growth factor (bFGF)plays an important role on the proliferation and differentiation of retinal progenitor cells,but its low intraocular permeability limits its clinical application.To explore an effective approach to enhance the intraocular permeability of bFGF has an important significance for the treatment of retinopathy. Objective This study was to investigate the effect of azone on bFGF intraocular permeability after its topical administration. Methods Eighteen New Zealand white rabbits were randomly divided into four groups on random number table method.Distilled water( blank control group),5％ bFGF eyedrops(5％ bFGF group ),0.4％ azone+5％ bFGF eyedrops (0.4％ azone + 5％ bFGF group ) and 0.4％ azone+ 10％ bFGF eyedrops (0.4％ azone + 10％ bFGF group)were topically administered in different groups at 5- minute interval for 3 times.Aqueous and vitreous fluid were extracted 30 minutes after administration of eyedrops,and those in the 0.4％ azone + 5％ bFGF group were obtained 30,60 and 120 minutes after administration.bFGF concentration in the aqueous and vitreous fluid was quantified with ELISA. Results The bFGF levels(A value)in aqueous and vitreous fluid were 0.1007±0.0100 and 0.1340±0.0100 after topical administration of the 5％ bFGF eyedrops,those in blank control group were 0.1363 ±0.0100 and 0.1130±0.0100,respectively,and those in the 0.4％ azone+5％ bFGF group and 0.4％ azone+10％ bFGF group were significantly higher than the 5％ bFGF group ( both P=0.000).However,no significant difference was found in bFGF levels between 0.4％ azone+5％ bFGF group and 0.4％ azone + 10％ bFGF groups in both aqueous and vitreous fluid ( P =0.985,0.098 ).A value of bFGF in aqueous was gradually increased with prolong of time in the 0.4％ azone+5％ bFGF group,with the values 0.9413±0.0300 at 30 minutes,0.3865±0.0300 at 60 minutes,and 0.2550±0.0300 at 120 minutes,showing a positive linear correlation between bFGF level and time( R2 =0.736,P =0.003 ),but no significant correlation was seen in vitreous sample(R2=0.196,P=0.233). Conclusions Azone can improve the intraocular penetration of bFGF eyedrops.Increasing the concentration of bFGF in eyedrop from 5％ to 10％ dose not change its intraocular distribution.The highest content of the bFGF in aqueous is at 30 minutes following the administration of 0.4％ azone+5％ bFGF eyedrops. Key words: Azone; Basic fibroblast growth factor/eye drops; Permeability; Retinal progenitor cell

Evaluation of transdermal iontophoresis of enoxacin from polymer formulations: in vitro skin permeation and in vivo microdialysis using Wistar rat as an animal model

Polymers were used in vehicles to form hydrogel matrices in this study to evaluate the in vitro permeation and in vivo microdialysis of enoxacin. The highest transdermal delivery determined by area under flux-time curve (AUC) and intracutaneous enoxacin concentration were observed in methylcellulose (MC) and polyvinylpyrrolidone (PVP) hydrogels, respectively. To avoid the pH shift in vehicles during iontophoresis, buffer species were added to formulations to increase the buffer capacity. As expected, the permeability of enoxacin of anodal iontophoresis was larger than that of cathodal iontophoresis. Combination of benzalkonium chloride, a cationic surfactant as an enhancer, and iontophoresis exerted an enhancing effect for anionic enoxacin at pH 10.0. However, no effect or a negative effect was detected for cationic enoxacin in deionized water or pH 5.0 buffer, due to the shielding of the negative charge in the skin. The skin residue of enoxacin was slightly increased after the incorporation of Azone in PVP hydrogel. The result of in vivo microdialysis was in accordance with that of in vitro study. The effect of Azone on the intracutaneous enoxacin was more significant for in vivo microdialysis than in the in vitro study indicating the clinical feasibility of Azone for iontophoretic delivery. Microdialysis can be considered as a useful technique to investigate the pharmacokinetics of transdermal iontophoresis in vivo.

The effects of Azone and capsaicin on the permeation of naproxen through human skin

The permeation of naproxen through excised human skin and isolated perfused rabbit ear skin has been determined. It was found that both Azone and capsaicin enhanced the permeation with an enhancement ratio of up to 4-fold. The magnitudes of the effect were similar in human and rabbit skin. The permeation of naproxen from a saturated solution of the drug through skin pre-treated with Azone was similar to that from a commercial preparation (Naprosyn). In the perfused rabbit ear experiments the presence of capsaicin had no effect on the vasodilatation of the blood vessels, inferring that the penetration enhancement was a direct result of capsaicin influencing the barrier function of the skin. Structural similarities between Azone and capsaicin were seen using molecular graphics.

Effect of Azone on the iontophoretic transdermal delivery of metoprolol tartrate through human epidermis in vitro

This study was attempted to investigate the effect of Azone on the transdermal iontophoretic transport of metoprolol tartrate (MPL) through human epidermis in vitro. Investigations were done to probe the mechanism of action of this enhancer, and to see whether there is any synergistic effect of this enhancer in conjunction with iontophoresis. Along with comparison of iontophoretic and passive transport of the drug in presence of the enhancer, parameters like steady state flux (Jss), permeability coefficient (Kp) and enhancement factors (E) were evaluated. It was found that both during passive diffusion and iontophoresis, Azone caused increased transport of the drug through human epidermis and the transport was increased 130-fold during iontophoresis compared to passive flux. These results were supported by scanning electron microscopy studies of the epidermis after experimentation.

Azone® induced fluidity in human stratum corneum. A fourier transform infrared spectroscopy investigation using the perdeuterated analogue

The effect of Azone® on human stratum corneum (SC) lipid fluidity was investigated by the use of FT-IR spectroscopy and its perdeuterated analogue (D-azone). SC lipid fluidity was monitored in terms of the degree of organisation of the lipid acyl chains (reflected by changes in the frequency of the C-H 2 symmetric stretching frequency) and in terms of the rate of motion of the lipid chains within the ordered environment (reflected in changes in the bandwidth of the C-H 2 symmetric stretching frequency at half maximum height). Two levels of D-azone treatment were used. At the lower level results indicated that D-azone did induce disordering of the lipid acyl chains by the introduction of gauche conformers above the SC lipid gel to liquid crystalline phase transition midpoint (T m). The rate of motion of the chains was increased at lower temperatures indicating that D-azone did affect one aspect of SC lipid fluidity below T m. At the higher level of D-azone treatment the SC lipid fluidity was increased with respect to both aspects of fluidity examined, both above and below the SC lipid phase transition. This action could suggest how the penetration of molecules through the skin is enhanced by Azone. The data also seem to suggest a homogeneous distribution of D-azone through the SC lipid array.

The effect of the skin penetration enhancer Azone® on fatty acid-sodium soap-water mixtures

The effect of Azone on the phase behaviour of a mixture of partly neutralised fatty acids in water was investigated by X-ray diffraction. The lipid blend consisted of saturated palmitic chains and unsaturated oleic chains. It was found that the system consisted of both crystalline and liquid crystalline phases at body temperature and below. The solid phases consisted essentially of the saturated lipids, while the unsaturated lipids formed the liquid crystalline phase. Azone had a minor effect on the crystalline phase, but partitioned into the liquid crystalline phase. The addition of Azone caused the original reversed hexagonal phase to be transformed into a reversed micellar phase. The findings presented here are in line with our previous observations on the effect of Azone on the soya bean lecithin-water and monoolein-water system, but in conflict with another study on a similar fatty acid system where it was assumed that Azone promoted the formation of the lamellar phase.

Transdermal penetration enhancers in rabbit pinna skin: Duration of action, skin irritation, and in vivo/in vitro comparison

Irritation of the skin by chemical penetration enhancers may limit the use of these compounds in transdermal drug delivery. Biodegradable enhancers like dodecyl N,N-dimethylamino acetate (DDAA) have been synthesized previously to decrease the duration of action and toxicity of the enhancers. We studied the reversibility and extent of penetration enhancement and skin irritation by DDAA, Azone, and n-dodecanol in rabbit pinna skin using timolol and propranolol as penetrants. Also, in vitro and in vivo permeabilities of the drugs with and without enhancers were compared. Drug concentrations in diffusion chambers and rabbit plasma were determined using HPLC and radio receptor assay, respectively. Skin irritation was measured with a chromameter. DDAA and Azone caused approximately equal transdermal penetration enhancement of model drugs in vitro but the potency of n-dodecanol was lower. In vivo, Azone was the most irritating enhancer in rabbit pinna skin. Both enhancer effects and skin irritation by DDAA were reversed in 4 days, while the effects of Azone and n-dodecanol lasted longer. Thus, it is possible to affect the duration of skin alteration by enhancer design. Propranolol was more irridating than timolol in rabbit pinna skin in vivo. Percutaneous permeability of propranolol in vivo, calculated from pharmacokinetic parameters, was considerably greater than its in vitro permeability coefficient. In contrast, in vitro and in vivo permeability coefficients of timolol were comparable. The increased permeation of propranolol in vivo may be due to skin irritation, because in vivo permeability coefficients correlated with associated skin irritation.

In vitro penetration of the dopamine D2 agonist N-0923 with and without Azone

Abstract The penetration of the dopaminergic D2 agonist S (−)-2-( N -propyl- N -2-thienylethylamino)-5-hydroxytetralin (N-0923) was evaluated in vitro on full-thickness rat skin, using the Franz diffusion cell. The drug was tested as the N-0923 · HCl salt as well as the N-0923 base. The penetration-enhancing effect of Azone was studied in a vehicle concentration of 5%, or after pretreating shaven rat skin in vivo, at several time intervals before the in vitro experiment, with a solution containing 1 or 5% Azone. From the vehicle containing 60% ethanol, 20% propylene glycol and 20% water, the extent of penetration through rat skin was relatively low for the base and even lower for the salt. The introduction of Azone into the vehicle in a final concentration of 5% resulted in a 6-fold decrease in penetration for the free base. Nevertheless, penetration of the salt increased about 12-fold in extent during the first 12 h, after which it declined to almost zero. The lag time was reduced from 13 to 5 h. Pretreatment of rat skin in vivo with an ethanol-propylene glycol-water solution containing 5% Azone resulted in a 12-fold increase in flux for the salt, a 2-fold increase in flux for the base and a decrease in lag time to about the same values for both N-0923 · HCl and N-0923 base. In vivo pretreatment of rat skin with a solution containing 1% Azone had no significant effect on the flux and lag time vs controls. This study indicates that Azone may have potential in facilitating the transdermal application of N-0923, principally through pretreatment of the skin to enhance absorption. This may allow it to circumvent its considerable oral first-pass metabolism.

Mechanism of Skin Penetration-Enhancing Effect by Laurocapram

In order to clarify the mechanism of action of laurocapram (Azone) on the skin permeation of drugs, the following experiments were done. First, the effect of Azone on the skin components was compared with that of other penetration enhancers. Azone markedly fluidized liposomal lipids (as a model lipid system) compared with other enhancers. Ethanol extracted large amounts of the stratum corneum lipids, whereas Azone did not. These results suggest that the effect of Azone on the lipids in the stratum corneum is not the same as that of ethanol. In addition, ethanol increased the amount of free sulfhydryl (SH) group of keratin in the stratum corneum, whereas Azone did not directly affect the stratum corneum protein. Azone increased water content in the stratum corneum, as measured by skin conductance. This effect might be a reason for the action of Azone. For further understanding, the enhancing effects of Azone on the skin permeation of several model compounds (alcohols, sugars, and inorganic ions) were compared with the effects of pretreatment with distilled water, which was thought to increase water-holding capacity, and pretreatment with ethanol, which was thought to affect the lipids and protein in the skin barrier (i.e., stratum corneum). Pretreatment with water or ethanol enhanced skin permeation of hydrophilic compounds, whereas they decreased that of octanol, a hydrophobic compound. The tendency of Azone to increase or decrease the skin permeation rate of most compounds was similar to that of pretreatment with water or ethanol. However, the effect of Azone on the skin permeation of inorganic ions was relatively low, whereas that of pretreatment with water or ethanol was high. We then hypothesized three permeation routes in the skin: a lipid-rich route, where hydrophobic compounds can permeate; a water-rich route, where relatively hydrophilic compounds can permeate; and a pore (shunt) route, where even inorganic ions can permeate. Azone may act on the lipid-rich route because it fluidizes the stratum corneum lipids, but also on the water-rich route because it enriches the water content. In general, increase in the pore (shunt) route would be expected when lipid has been extracted by enhancers or solvents such as ethanol. Therefore, the effect of Azone on the enlargment in the pore (shunt) route may be negligible. The reason why Azone affects the skin permeation of a relatively broad spectrum of drugs may be that it affects at least two permeation routes in the skin barrier.

Effects of transdermal penetration enhancers on the permeability of shed snakeskin.

The effects of Azone and lauryl alcohol on the permeability of shed snakeskin were examined. Permeability of a variety of compounds through shed snakeskin was increased after Azone or lauryl alcohol pretreatment but the magnitude of the enhancement varied depending on the lipophilicity and the molecular size of the permeant. It was found that the shed snakeskin became more permeable after Azone or lauryl alcohol pretreatment, with a greater permeability increase for more hydrophilic and larger-molecular size permeants. As has been shown for untreated shed snakeskins, both the lipophilicity and the molecular size of the permeants are important in skin penetration and in determining the effects of transdermal penetration enhancers.

Effect of Ph on Enhancement of in Vitro Percutaneous Transport of Isoproterenol Hcl by Azone

AbstractThis in vitro study examined the effect of Azone on skin permeability of isoproterenol HC1 at pH of 2.0, 8.0, 6.5 and 9.0. Azone was found to enhance the percutaneous transport of the drug from an aqueous vehicle under the pH conditions studied. The flux across human cadaver skin increased with increasing vehicle pH for Azone-treated and untreated skin with an observed maximum at pH 9.0.

Transdermal permeation of vasopressin. II. Influence of Azone on in vitro and in vivo permeation

Different enhancers were evaluated by measuring in vitro diffusion of aqueous vasopressin solution through excised rat skin after pretreatment with enhancers. Azone was found to be the most effective enhancer studied, increasing the flux about 15 times. Concentrations of Azone higher than 3% v/v did not show any further enhancement of flux. The enhancement of flux by Azone in hairless mouse skin was more dramatic (about 70 times), suggesting that the mechanism of enhancement in hairless mouse skin might be different than in the rat. The effect of Azone was evaluated in vivo using adult vasopressin-deficient Brattleboro rats. Urine was collected at time intervals after topical administration of vasopressin, and urine volume, osmolality and radioactivity were determined. Significant reduction in urine volume and increase in osmolality over a 24 h period confirmed the enhancement of vasopressin absorption in presence of Azone found in vitro.

Dose-dependent enhancement effects of azone on skin permeability.

In vitro permeability experiments have been combined with differential scanning calorimetry (DSC) studies in an attempt to address the dose-dependent influence of Azone on the permeability coefficients of solutes for hairless mouse stratum corneum. A spray technique was developed to deliver uniformly and quantitatively small amounts of Azone to the stratum corneum. Permeability data obtained for several model solutes of varying lipophilicity suggest lipid fluidization and polar route enhancement as the mechanisms of action for Azone. Alkanols and steroids, both of which are enhanced primarily by lipid fluidization, had different degrees of relative enhancement. This provides evidence that the stratum corneum barrier is heterogeneous, rather than a homogeneous slab barrier. Two effects of Azone on the stratum corneum were detected by DSC. A decrease in the area and a shift to lower temperatures were noted for the lipid endotherms with increasing doses of Azone. A lipid fluidizing effect would qualitatively account for the increases in the permeability coefficients noted for more lipophilic solutes. The stratum corneum keratin endotherm also appears to be altered in the presence of Azone. It is possible that alteration of the keratin structure could lead to the development of polar routes in the stratum corneum.

The effect of azone on ocular levobunolol absorption: calculating the area under the curve and its standard error using tissue sampling compartments.

Methods of calculating the area under the concentration-time curve and the associated standard error are proposed for studies in which each animal contributes one independent data point to a pool of data. This approach can be used for data analysis in bioequivalence studies employing tissue sampling compartments. Application of this method indicated that an azone-containing ophthalmic formulation of levobunolol did not produce better ocular bioavailability than a formulation containing no penetration enhancer.

Transdermal delivery of isoproterenol HCl: an investigation of stability, solubility, partition coefficient, and vehicle effects.

Effects of solubility, partition coefficient, and selected adjuvants (propylene glycol and Azone) on percutaneous penetration of isoproterenol HCl have been investigated using human cadaver skin. Isoproterenol was found to be stable (less than 1% decomposition) for 24 hr at 22 +/- 0.5 degrees C in the pH range 1 to 7 in the following solvents: water, normal saline, propylene glycol and a series of propylene glycol-water mixtures (10, 20, 40, and 60%; v/v); however, decomposition was significant beyond pH 8. In normal saline, the rate of decomposition increased significantly with an increase in temperature to 37 degrees C. The solubility of isoproterenol HCl decreased and its skin/vehicle partition coefficient increased with increasing proportions of propylene glycol in the vehicle, while the product of the solubility and partition coefficient appeared to plateau at 20% propylene glycol in water. Optimal penetration enhancing effects of Azone were seen when incorporated at a concentration of 1% (v/v) in the 20% (v/v) propylene glycol-water blend and, more significantly, when skin was pretreated with pure Azone for 60 min prior to application of the drug formulation.

Effect of Azone on the percutaneous absorption of 5-fluorouracil from gels in hairless rats.

Poly (acrylic acid) gels containing 5-fluorouracil (5-FU) and Azone were prepared and the effects of Azone on 5-FU release from the gels and on 5-FU permeation across the skin were studied by in vitro and in vitro methods. 5-FU was released rapidly from the gels. The release rate of 5-FU from the gels was higher than that from a commercial ointment. Azone did not affect the in vitro drug release from the gels. Experiments on in vitro permeation of 5-FU across the hairless rat skin with vertical diffusion cells showed that addition of Azone to the gels markedly enhanced the 5-FU permeability, although a lag time of approximately 6 h was observed. Increasing the Azone concentration in the gels to 15% proportionally increased the permeability of 5-FU. More than 10 h was required to reach a steady-state blood level of 5-FU after administration of 5-FU-Azone gel topically. Pretreatment with Azone, however, shortened the lag time so that a steady-state level was reached sooner. The area under the blood concentration-time curve (AUC) after topical administration was comparable to that after oral administration.These results suggest not only that Azone would be very useful for increasing the skin permeability and blood level of 5-FU, but also that Azone might be useful for developing transdermal therapeutic systems for the delivery of practically unabsorbable drugs.

Dermal drug delivery — Improvement by choice of vehicle or drug derivative

Propylene glycol was found to easily permeate human skin in vitro, and its accelerating effect on metronidazole permeation could be ascribed to a possible “carrier-solvent” effect. Incorporation of Azone ® in propylene glycol vehicles enhanced the permeation rate by decreasing the lag time of permeation of the drug as well as propylene glycol from the vehicle. This effect of azone lasted for the subsequent application of the drug where ozone was omitted from the vehicle, indicating that the accelerant might modify the cutaneous barrier in vitro. Pro-drug derivatives of metronidazole and of 5-fluorouracil have been developed which permit increased cutaneous drug permeation and simultaneously undergo conversion to the parent drug by the cutaneous hydrolytic enzymes. Enzyme-mediated hydrolysis by a human skin homogenate of aliphatic esters of metronidazole is presented.

Vehicle effect on topical drug delivery. III. Effect of Azone on the cutaneous permeation of metronidazole and propylene glycol

The ability of Azone (1-dodecylazacycloheptan-2-one), a novel penetration enhancer, to increase the percutaneous delivery of metronidazole has been investigated, across full thickness human skin in vitro. A finite dose technique was used employing several vehicles. Azone at a concentration of 1% was found to be as effective as 5% and 10% concentrations in achieving enhanced transport of metronidazole. The presence of propylene glycol was found to be necessary for maximal enhancement, and the penetration of this compound was also found to be markedly enhanced by Azone. The delivery of metronidazole within the first 20 h of the experiments was increased about 25 times in the presence of 1% Azone. Repeated doses of the drug after a single dose of Azone indicated that the effect of Azone on the skin remains after several days.

Effect of azone and propylene glycol on penetration of trifluorothymidine through skin and efficacy of different topical formulations against cutaneous herpes simplex virus infections in guinea pigs

Tropical formulations of 5-trifluoromethyl-2'-deoxyuridine (TFT) containing different concentrations of TFT, Azone (Nelson Research and Development, Irvine, Calif.), and propylene glycol were evaluated for their potential efficacy in the treatment of cutaneous herpes simplex virus infections by in vitro studies of TFT penetration through skin and in vivo studies of therapeutic activity against herpes simplex virus type 1 infections in the dorsal cutaneous guinea pig model. Azone dramatically increased TFT penetration through human and guinea pig skin. Unexpectedly, high concentrations of propylene glycol were also associated with increased penetration. Studies in the guinea pig model revealed increased efficacy with Azone-propylene glycol-containing formulations, consistent with the in vitro drug diffusion results. A formulation containing 1% TFT, 5% Azone, and 80% propylene glycol decreased lesion area, in comparison to the drug vehicle control, more effectively than 5% acyclovir in polyethylene glycol (reduction of 70 versus 46%, P = 0.03). These studies demonstrate the value of penetration-enhancing agents and the need for careful preclinical evaluations in the development of topical antiviral agents.