title: Skin permeation of lidocaine from crystal suspended oily formulations.
abstract: In vitro permeation of lidocaine (lidocaine base, LID) through excised rat skin was investigated using several LID-suspended oily formulations. The first skin permeation of LID from an LID-suspended oily solution such as liquid paraffin (LP), isopropyl myristate (IPM), polyoxyethylene (2) oleylether (BO-2), and diethyl sebacate (DES) was evaluated and compared with that from polyethylene glycol 400 (PEG400) solution, a hydrophilic base. The obtained permeation rate of LID, Japp, from PEG400, LP, IPM, BO-2, and DES was in the order of DES>BO-2=IPM>LP>PEG400, and increased with LID solubility in the oily solvents, although LID crystals were dispersed in all solvents. Subsequently, oily formulations that consisted of different ratios of the first oily solvent (IPM, BO-2, or DES) (each 0-20%), the second oily solvent (LP) and an oily mixture of microcrystalline wax/white petrolatum/paraffin (1/5/4) were evaluated. BO-2 groups at a concentration of 5% and 10% had the highest Japp among the oily formulations, although a higher BO-2 resulted in lower skin permeation. In addition, pretreatment with BO-2 increased the skin permeation of LID. These results suggest that the penetration enhancing effect by the system may be related to the skin penetration of BO-2 itself. Finally, mathematical analysis was done to evaluate the effect of BO-2, and it was shown that BO-2 improved the LID solubility in stratum corneum lipids to efficiently enhance the LID permeation through skin.
authors.affiliation: H&BC Research Center, Shiseido Research Center, Yokohama, Japan. rakan.matsui@to.shiseido.co.jp
authors.forename: Rakan
authors.initials: R
authors.lastname: Matsui
authors.forename: Masaaki
authors.initials: M
authors.lastname: Hasegawa
authors.forename: Masami
authors.initials: M
authors.lastname: Ishida
authors.forename: Toshiya
authors.initials: T
authors.lastname: Ebata
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Namiki
authors.forename: Kenji
authors.initials: K
authors.lastname: Sugibayashi
mesh_terms: D000779:Anesthetics, Local / Q000737:chemistry / Q000493:pharmacokinetics*; D000818:Animals; D002626:Chemistry, Pharmaceutical; D003460:Crystallization; D003652:Decanoic Acids / Q000494:pharmacology; D066298:In Vitro Techniques; D008012:Lidocaine / Q000737:chemistry / Q000493:pharmacokinetics*; D008297:Male; D008899:Mineral Oil / Q000494:pharmacology; D009226:Myristates / Q000494:pharmacology; D010539:Permeability; D014677:Pharmaceutical Vehicles; D011092:Polyethylene Glycols / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012869:Skin Absorption / Q000187:drug effects*; D012995:Solubility
chemical_list: D000779:Anesthetics, Local; D003652:Decanoic Acids; D009226:Myristates; D014677:Pharmaceutical Vehicles; C478746:polyoxyethylene-10-oleyl ether; C008205:isopropyl myristate; D011092:Polyethylene Glycols; D008899:Mineral Oil; D008012:Lidocaine; C029410:ethyl sebacate