title: Noninvasive percutaneous induction of topical analgesia by a new type of drug carrier, and prolongation of local pain insensitivity by anesthetic liposomes.
abstract: We studied the duration of action and permeability of common analgesics and local anesthetics applied dermally via new carriers--transfersomes--in rats and humans. The therapeutic potential of analgesic transfersomes was evaluated in Sprague-Dawley rats subjected to heat and pressure stimuli. Results were compared with those obtained from administration of lidocaine-containing standard liposomes. In rats, subcutaneous injections of 2% lidocaine solution and of liposomal or transfersomal suspension resulted in a strong initial analgesic effect that decayed within 6-7 min. Characteristic withdrawal time is approximately 30 s. Dermally applied analgesic transfersomes, by contrast, increased heat stimulus reaction to greater than 70 s, 130% longer than in controls that received a placebo or a standard aqueous lidocaine solution. In humans, we tested two groups of nine male and female volunteers, aged between 25 and 60 yr, for pain-suppressing activity assessed by the pinprick method. Each subject received a total of 0.5 mL of a transfersomal preparation containing 7% lidocaine or 4% tetracaine over a forearm area of 9 cm. We conclude that the effectiveness of dermally applied anesthetic transfersomes is similar to that of the corresponding subcutaneous injections of similar drug quantities and that optimally designed transfersomes offer a suitable and promising means for the noninvasive treatment of local pain with direct, topical drug application.
authors.affiliation: Department of Pharmacology and Therapeutic Chemistry, University of Barcelona, Faculty of Odontology, Hospitalet de Llobregat, Spain.
authors.forename: M E
authors.initials: ME
authors.lastname: Planas
authors.forename: P
authors.initials: P
authors.lastname: Gonzalez
authors.forename: L
authors.initials: L
authors.lastname: Rodriguez
authors.forename: S
authors.initials: S
authors.lastname: Sanchez
authors.forename: G
authors.initials: G
authors.lastname: Cevc
mesh_terms: D000279:Administration, Cutaneous; D000328:Adult; D000700:Analgesics / Q000008:administration & dosage*; D000818:Animals; D004337:Drug Carriers; D005260:Female; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage; D008081:Liposomes; D008297:Male; D008875:Middle Aged; D051381:Rats; D011919:Rats, Inbred Strains; D013748:Tetracaine / Q000008:administration & dosage; D013997:Time Factors
chemical_list: D000700:Analgesics; D004337:Drug Carriers; D008081:Liposomes; D013748:Tetracaine; D008012:Lidocaine