title: Formulation and efficacy studies of new topical anesthetic creams.
abstract: Local anesthetics (lidocaine or tetracaine) spontaneously melted at 25 degrees C when mixed with thymol and aqueous isopropyl alcohol solution (IPA) at proper ratios and formed novel two-phase melt systems (TMS). The TMS consisted of a homogeneous oil phase containing primarily a local anesthetic agent (lidocaine or tetracaine) and thymol, and a homogeneous aqueous phase containing primarily IPA and pH 9.2 buffer. The relationship between melting of the solid components and system composition was determined from the phase diagram obtained by a titration method. A select TMS of a local anesthetic agent (lidocaine or tetracaine) was directly emulsified to prepare an O/W cream and tested for the anesthetic efficacy on intact human skin. While both lidocaine (6%) and tetracaine (4%) creams were highly effective for dermal anesthesia with a similar onset time, the tetracaine cream exhibited a significantly longer duration of action than the lidocaine cream. An accelerated stability study indicated that lidocaine was significantly more stable than tetracaine in the creams.
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, The University of Georgia College of Pharmacy, Athens, Georgia 30602, USA.
authors.forename: Lisheng
authors.initials: L
authors.lastname: Kang
authors.forename: H W
authors.initials: HW
authors.lastname: Jun
mesh_terms: D019840:2-Propanol / Q000737:chemistry; D000279:Administration, Cutaneous; D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000737:chemistry* / Q000494:pharmacology; D004339:Drug Compounding; D004355:Drug Stability; D005260:Female; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009824:Ointments; D010316:Particle Size; D012867:Skin / Q000187:drug effects*; D012996:Solutions; D013748:Tetracaine / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology; D013943:Thymol / Q000737:chemistry; D014783:Viscosity
chemical_list: D000779:Anesthetics, Local; D009824:Ointments; D012996:Solutions; D013748:Tetracaine; D013943:Thymol; D008012:Lidocaine; D019840:2-Propanol