title: Iontophoretic transdermal delivery of glycyrrhizin: effects of pH, drug concentration, co-ions, current intensity, and chemical enhancers.
abstract: The aim of the present study was to evaluate the feasibility of transdermal delivery of glycyrrhizin, an agent used in the treatment of chronic hepatitis C, by cathodal iontophoresis using Ag/AgCl electrodes in vitro. The effects of donor pH (pH 4-7), concentration of drug (0.025-0.2% (w/v)), concentration of external chloride ions (Cl(-)) (0-133 mM), current strength (0-0.5 mA/cm(2)), and permeation enhancers (urea and Tween 80) on the skin permeability of glycyrrhizin were examined in in vitro skin permeation studies using porcine ear skin as the membrane. The cumulative amount of permeated glycyrrhizin and the steady-state skin permeation flux of glycyrrhizin across porcine skin increased in a pH-dependent manner. The skin permeability of glycyrrhizin was independent of the concentration of drug and competed only with a high external Cl(-) concentration. The skin permeation flux of glycyrrhizin increased with the current (R(2)=0.8955). The combination of iontophoresis and enhancers provided an additive or synergistic effect, and a skin permeation flux of about 60 µg/h/cm(2) was achieved. The plasma concentration of glycyrrhizin in humans, extrapolated from the in vitro steady-state permeation flux across porcine skin, was within the therapeutic level. These results suggest that cathodal iontophoresis can be used as a transdermal drug delivery system for glycyrrhizin using reasonable patch sizes and acceptable levels of current intensity.
authors.affiliation: Department of Device Development, TTI ellebeau, Inc.
authors.forename: Rie
authors.initials: R
authors.lastname: Yamamoto
authors.forename: Shinri
authors.initials: S
authors.lastname: Takasuga
authors.forename: Katsuya
authors.initials: K
authors.lastname: Kominami
authors.forename: Chiyo
authors.initials: C
authors.lastname: Sutoh
authors.forename: Mine
authors.initials: M
authors.lastname: Kinoshita
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kanamura
authors.forename: Kozo
authors.initials: K
authors.lastname: Takayama
mesh_terms: D000279:Administration, Cutaneous; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D016503:Drug Delivery Systems / Q000379:methods*; D019695:Glycyrrhizic Acid / Q000008:administration & dosage* / Q000097:blood / Q000493:pharmacokinetics; D006801:Humans; D007478:Iontophoresis / Q000379:methods*; D008297:Male; D011136:Polysorbates / Q000494:pharmacology; D012867:Skin / Q000187:drug effects / Q000378:metabolism*; D012869:Skin Absorption / Q000187:drug effects; D013552:Swine; D014508:Urea / Q000494:pharmacology
chemical_list: D000893:Anti-Inflammatory Agents; D011136:Polysorbates; D019695:Glycyrrhizic Acid; D014508:Urea