Transdermal Delivery of Cytochrome C—A 12.4kDa Protein—Across Intact Skin by Constant-Current Iontophoresis

Purpose: To demonstrate the transdermal iontophoretic delivery of a small (12.4kDa) protein across intact skin. Materials and Methods: The iontophoretic transport of Cytochrome c (Cyt c) across porcine ear skin in vitro was investigated and quantified by HPLC. The effect of protein concentration (0.35 and 0.7mM), current density (0.15, 0.3 or 0.5mA.cm−2 applied for 8h) and competing ions was evaluated. Co-iontophoresis of acetaminophen was employed to quantify the respective contributions of electromigration (EM) and electroosmosis (EO). Results: The data confirmed the transdermal iontophoretic delivery of intact Cyt c. Electromigration was the principal transport mechanism, accounting for ∼90% of delivery; correlation between EM flux and electrophoretic mobility was consistent with earlier results using small molecules. Modest EO inhibition was observed at 0.5mA.cm−2. Cumulative permeation at 0.3 and 0.5mA.cm−2 was significantly greater than that at 0.15mA.cm−2; fluxes using 0.35 and 0.7mM Cyt c in the absence of competing ions (J tot  = 182.8 ± 56.8 and 265.2 ± 149.1μg.cm−2.h−1, respectively) were statistically equivalent. Formulation in PBS (pH8.2) confirmed the impact of competing charge carriers; inclusion of ∼170mM Na+ resulted in a 3.9-fold decrease in total flux. Conclusions: Significant amounts (∼0.9mg.cm−2 over 8h) of Cyt c were delivered non-invasively across intact skin by transdermal electrotranspor

Ex vivo oral mucosal permeation of lidocaine hydrochloride with sucrose fatty acid esters as absorption enhancers

The ex vivo permeation of lidocaine hydrochloride, a model drug, was studied in two different regions of the oral mucosa: pig palate (keratinized) and cheek (non-keratinized). The enhancing effect of a series of sucrose fatty acid esters (nonionic surfactants), which have the advantage of reduced irritation potential relative to other enhancers, was investigated. Among the sucrose esters tested, an increase in the passage of lidocaine through buccal and palatal mucosae was observed only for sucrose laurate (L-1695) (enhancement ratio (ER) ∼22 for buccal and ∼14 for palatal mucosa). The other sucrose esters (S-1670, O-1570 and P-1670), did not show any promoting effect. The type of fatty acid sucrose ester, was found to be a key factor for promoting the absorption of lidocaine. The contribution of sucrose esters was compared with that of other enhancers, such as ethanol, oleic acid and Transcutol®. A significant enhancing effect was observed with oleic acid/hydroalcoholic solution, for both buccal and palatal mucosa (ER ∼13 and ∼61, respectively). However, there was no promotion when the hydroalcoholic solution was applied in the absence of oleic acid. A synergic effect between oleic acid and ethanol is very probable. A slight promoting effect was obtained when Transcutol/water (50:50) was used as the vehicle

Contribution of lipid components to the permeability barrier of oral mucosa

The aim of this paper is to review the lipid composition of different regions of the oral mucosa, bearing in mind that, in general, molecular diffusion occurs through the intercellular lipids. Lipid content and organization is described to explain the permeability differences between keratinized and nonkeratinized tissues. Some of the thermotropic and lyotropic transitions observed in simple lipid model systems, such as liposomes, are also taken into consideration, in an attempt to explain the contribution of each lipid class to the permeability barrier

The effect of keratolytic agents on the permeability of three imidazole antimycotic drugs through the human nail

The permeability of three imidazole antimycotics (miconazole nitrate, ketoconazole, and itraconazole) through the free edge of healthy human nail was evaluated in vitro using side-by-side diffusion cells. The influence of keratolytic substances (papain, urea, and salicylic acid) on the permeability of the antimycotics was also studied. The results suggested that the nail constituted an impermeable barrier for these antimycotics; it could be considered that the nail behaved as a hydrophilic gel membrane, through which drugs of low solubility could not permeate. The use of ethanol did not promote the passage of any of the antimycotic drugs. Although scanning electron microscopy indicated that the keratolytic substances had a significant effect on the nail surface (papain > salicylic acid > urea), the passage of the three antimycotics was not improved by pretreatment with salicylic acid alone (20% for 10 days), or by the application of the drug in a 40% urea solution. It was found that only the combined effects of papain (15% for 1 day) and salicylic acid (20% for 10 days) were capable of enhancing the permeability of the antimycotic

Skin permeation enhancement by sucrose esters: a pH-dependent phenomenon

The purpose of the present study was to evaluate the effect of sucrose esters (particularly, sucrose laureate and sucrose oleate in Transcutol) on the percutaneous penetration of a charged molecule as a function of ionization. We have investigated the influence of these sucrose esters on the in vitro diffusion profiles of lidocaine hydrochloride, a weak ionizable base (pKa=7.9), at different pH values, using porcine ear skin as the barrier membrane. As expected, lidocaine flux in the absence of an enhancer, increased from pH 5 to 9 with a corrresponding increase in the level of the unionized base. However, when skin was pretreated with 2% laureate in Transcutol (2% L-TC), drug permeation was higher at pH 5.0 and 7.0 than at 9.0. A different trend was observed in experiments with 2% oleate in Transcutol (2% O-TC), where skin flux was maximal at a more basic pH, when the degree of ionization is low. The results suggest that sucrose laureate enhances the penetration of the ionized form of the drug (12-fold greater flux relative to control), whereas sucrose oleate is more effective in promoting permeation of the unionized species. The structural properties of the sucrose esters as well as the degree of ionization of the drug are important characteristics affecting the transdermal flux of lidocaine

Mechanisms of oral permeation enhancement

This paper reviews the effects of a diverse range of penetration enhancers, including fatty acids, bile salts, surfactants, Azone® and ethanol, on oral mucosa. We describe in detail the effects on the intercellular lipid domains, the changes induced in proteinaceous regions and potential interactions between the enhancer and endogenous structures along the transport pathway. Since there have been few structure-based studies of the oral mucosa, which have discussed enhancer effect as a function of specific physicochemical properties, we have drawn upon analogous studies of skin and other mucosal membranes, as well as model lipid systems, e.g. liposomes

Evaluation of the transepidermal permeation of diethylene glycol monoethyl ether and skin water loss

The rate of Transcutol® (TC)-water interchange, was studied using whole and stripped hairless rat skin in a modified vertical Franz diffusion cell. The presence of stratum corneum limited the passage of the two solvents, but after stripping of the skin, the rate of TC transfer increased and the water flow rose until the vapour pressure at the skin surface and in the ambient air was similar. The results suggest that TC increased the donor hydration by increasing the outflow of water, with a change in the donor composition. These two opposite fluxes and the alteration of the bulk constitution of the skin and of the donor compartment throughout the experiment, are important factors to be considered for the permeation studies with this solvent

Effects of sucrose oleate and sucrose laureate on in vivo human stratum corneum permeability

The purpose of this work was to 1) investigate the effect of sucrose esters (sucrose oleate and sucrose laureate in water or in Transcutol, TC) on the stratum corneum (SC) barrier properties in vivo and 2) examine the impact of these surfactant-like molecules on the in vivo percutaneous penetration of a model penetrant 4-hydroxybenzonitrile (4-HB)

Applications of thermo-reversible pluronic F-127 gels in pharmaceutical formulations

It is, sometimes, desirable to maintain a constant plasma drug concentration within the therapeutically effective concentration range. The use of high viscosity hydromiscible vehicles such as hydrophilic gels, is one of various approaches for controlled drug delivery, and represents an important area of pharmaceutical research and development. Of these systems, Pluronic F-127 (PF-127) provides the pharmacist with an excellent drug delivery system for a number of routes of administration and is compatible with many different substances. Gels containing penetration enhancers have proven to be especially popular for administering anti-inflammatory medications since they are relatively easy to prepare and very efficacious

Comparison of the ex-vivo oral mucosal permeation of tryptophan-leucine (Trp-Leu) and its myristoyl derivative

The ex vivo permeation of a model peptide, tryptophan-leucine (Trp-Leu), was studied using two different regions of pig oral mucosa, the hard palate and the cheek. In order to increase the mucosal absorption of Trp-Leu, a lipophilic derivative was synthesized by acylation of the N-terminal amino group of Trp-Leu with myristic acid. The purified Trp-Leu derivative (Myr-Trp-Leu) was more lipophilic than the parent Trp-Leu as observed by HPTLC (Rf's values of 0.41 and 0.81, respectively). Measurement of partition coefficients in n-octanol/phosphate buffer pH 7.4, gave Kp values of −0.68 and 1.04 for Trp-Leu and Myr-Trp-Leu, respectively. The native Trp-Leu was unable to pass through the keratinized layer of palatal mucosa, and after 24 h only 12% had passed through the buccal mucosa to the receptor compartment. The higher lipophilicity of the acylated peptide, meant that it was not easily transported across the oral mucosal barrier but accumulated in the tissue, founding 25 and 70% of the original amount in the palatal and buccal mucosae, respectively. Both, Trp-Leu and Myr-Trp-Leu were found to be stable in palatal and buccal mucosae