title: Cutaneous analgesia after transdermal application of amitriptyline versus lidocaine in rats.
abstract: Amitriptyline, a tricyclic antidepressant, has potent local anesthetic properties. However, there is no report of cutaneous analgesic effects after transdermal application. We report here that transdermally applied amitriptyline is more potent than lidocaine in providing cutaneous analgesia in rats. Solutions of amitriptyline base in 50, 100, and 500 mM concentrations were applied as a patch to rats, and their effects were compared with those of lidocaine base at the same concentrations and of the vehicle alone (45% water, 45% isopropyl alcohol, and 10% glycerin). Rats in each test group developed a concentration-dependent cutaneous analgesic block in the areas to which the drugs were applied; however, amitriptyline produced a longer block than lidocaine at the same concentration. The development of amitriptyline as a longer-lasting topical analgesic may improve our ability to treat chronic pain, such as neuropathic pain and neuralgia, and to prevent pain in procedures such as venipuncture.
  
  
  CONCLUSIONS
  The tricyclic antidepressant amitriptyline, often used perorally for the management of chronic pain, is shown here to be more potent than lidocaine in providing cutaneous analgesia when applied transdermally with an occlusive dressing in rats.
authors.affiliation: *Department of Anesthesiology, Ried General Hospital, Ried, Austria; and †Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts.
authors.forename: Anna
authors.initials: A
authors.lastname: Haderer
authors.forename: Peter
authors.initials: P
authors.lastname: Gerner
authors.forename: Grace
authors.initials: G
authors.lastname: Kao
authors.forename: Venkatesh
authors.initials: V
authors.lastname: Srinivasa
authors.forename: Ging Kuo
authors.initials: GK
authors.lastname: Wang
mesh_terms: D000279:Administration, Cutaneous; D000639:Amitriptyline / Q000008:administration & dosage / Q000494:pharmacology*; D000700:Analgesics; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D000929:Antidepressive Agents, Tricyclic / Q000008:administration & dosage / Q000494:pharmacology*; D004890:Erythema / Q000139:chemically induced / Q000473:pathology; D008012:Lidocaine / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D010147:Pain Measurement / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D012018:Reflex / Q000187:drug effects; D012867:Skin / Q000187:drug effects*
chemical_list: D000700:Analgesics; D000779:Anesthetics, Local; D000929:Antidepressive Agents, Tricyclic; D000639:Amitriptyline; D008012:Lidocaine