ABSTRACT
Fatty acids classified as chemical penetration enhancers (CPEs) might cause the fluidization and perturbation of stratum corneum (SC) lipid matrix. The penetration of oleic, linoleic, lauric and capric acids into human skin was studied by time-of-flight secondary ion mass spectrometry (TOF-SIMS) imaging and related to fatty acids enhancing effect on lipophilic model drug tolnaftate penetration into human epidermis and dermis ex vivo. Fatty acid enhancing effect on tolnaftate penetration into human skin was evaluated using Bronaugh-type flow-through diffusion cells. After in vitro penetration studies visualization and spatial localization of fatty acid molecules in human skin were performed using TOF-SIMS. Penetration of oleic, linoleic, lauric and capric acids into human skin was compared to the control skin sections by ion images and intensity profiles. Only oleic acid significantly (P<0.05) enhanced tolnaftate penetration into epidermis (enhancing ratio equal to 1.867). CPE might have no effect on model drug penetration enhancement, but might penetrate itself into the skin.
Subject(s)
Fatty Acids/metabolism , Skin/metabolism , Spectrometry, Mass, Secondary Ion/methods , Decanoic Acids/metabolism , Humans , Lauric Acids/metabolism , Linoleic Acid/metabolism , Oleic Acid/metabolism , Oleic Acids/metabolismABSTRACT
Five fatty acids (oleic, linoleic, myristic, lauric and capric) were incorporated in 10% (w/w) into ointment formulation and their influence on lipophilic model drug tolnaftate release in vitro and enhancing effect on tolnaftate penetration into epidermis and dermis of human skin ex vivo were investigated. The prepared ointments were tested for homogeneity, pH and theological properties. In vitro release studies and ex vivo skin penetration experiments were carried out using Hanson and Bronaugh-type flow-through diffusion cells, respectively. Tolnaftate cumulative amount liberated from semisolids was assayed using UV-Vis spectrophotometer. After in vitro skin penetration studies, appropriately extracted human skin layers were analyzed for tolnaftate content using a validated HPLC method. Statistical analysis revealed that release rate of tolnaftate from control ointment and ointments with fatty acids was not significantly different and only 7.34-8.98% of drug was liberated into an acceptor medium after 6 h. Tolnaftate amount penetrating into 1 cm2 of epidermis from ointments containing oleic, linoleic, myristic and lauric acids was significantly greater (p < 0.05) than from the control ointment. Penetration enhancing ratios for these fatty acids for tolnaftate penetration into epidermis ranged from 1.48 to 1.75. In conclusion, fatty acids did not increase the liberation of tolnaftate from ointment formulation, but demonstrated their enhancing effect on tolnaftate penetration into human epidermis in vitro. Results from in vitro release experiments do not suit for prediction of the situation in the skin in vitro, if chemical penetration enhancers are incorporated into the ointment formulation.
Subject(s)
Antifungal Agents/metabolism , Fatty Acids/pharmacology , Skin Absorption/drug effects , Skin/drug effects , Tolnaftate/metabolism , Administration, Cutaneous , Adult , Antifungal Agents/administration & dosage , Antifungal Agents/chemistry , Chemistry, Pharmaceutical , Chromatography, High Pressure Liquid , Decanoic Acids/pharmacology , Drug Compounding , Fatty Acids/administration & dosage , Fatty Acids/chemistry , Female , Humans , Hydrogen-Ion Concentration , Kinetics , Lauric Acids/pharmacology , Linoleic Acid/pharmacology , Middle Aged , Myristic Acid/pharmacology , Ointments , Oleic Acid/pharmacology , Permeability , Rheology , Skin/metabolism , Solubility , Spectrophotometry, Ultraviolet , Technology, Pharmaceutical/methods , Tolnaftate/administration & dosage , Tolnaftate/chemistryABSTRACT
Abstract: Tolnaftate, an antifungal of thiocarbamate class, is used topically in 1% formulations. Its penetration into skin layers is a prerequisite for tolnaftate action against dermatophytes. The aim of this work was to optimize and validate a simple, rapid, accurate and reproducible procedure for tolnaftate assay in human skin samples and to apply this procedure for in vitro tolnaftate penetration studies. High performance liquid chromatography (HPLC) method with UV detection was used to validate tolnaftate assay for linearity, specificity, accuracy, precision, limit of quantitation, limit of detection, drug extraction recovery and stability in skin extracts. In vitro tolnaftate penetration studies were carried out using flow-through diffusion cells, mounted with human skin. Epidermis and dermis, separated by heat-separation method, were extracted using ultrasonication in methanol. Linear range of the analytical procedure was within 0.6-100 pg/mL. The assay was specific, accurate (within-day and between-day recovery values were 98.2-104.2% and 98.7-101.4%, respectively) and precise (within-day and between-day imprecision was = 3.8%). Mean extraction recoveries of tolnaftate from epidermis and dermis were satisfactory and reaching 90%. In vitro skin penetration studies revealed that after application of 1% (w/w) tolnaftate solution in polyethylene glycol 400 for 24 hours, the mean amount of tolnaftate penetrating into the epidermis and dermis was 2.60 +/- 0.28 microg/cm2 and 0.92 +/- 0.12 microg/cm2, respectively. A validated reliable HPLC method could be recommended for biopharmaceutical evaluation of tolnaftate preparations and studies of pharmacokinetics in human skin after in vitro penetration studies.
