title: Pain-relieving effects of intravenous ATP in chronic intractable orofacial pain: an open-label study.
abstract: OBJECTIVE
  Chronic orofacial pain is often refractory to conventional pain therapies. We conducted an open-label study to determine whether adenosine 5'-triphosphate (ATP) could alleviate chronic intractable orofacial pain, and if so, which type of pain could respond to ATP.
  
  
  METHODS
  In 8 and 16 patients with non-neuropathic and neuropathic intractable orofacial pain, respectively, ATP was intravenously infused at a rate of 100 microgxkg(-1)xmin(-1) over 120 min. The magnitudes of spontaneous pain and brush-evoked allodynia were graded with a visual analog scale (VAS). When a VAS score for spontaneous pain was decreased by 50% or more by ATP, the patient was classified as a responder.
  
  
  RESULTS
  The patients could be clearly divided into 10 responders and 14 non-responders. Ten of the 16 patients (62.5%) with neuropathic pain, but none of the 8 patients with non-neuropathic pain, responded to ATP. In particular, all of 8 patients with neuropathic pain following pulpectomy, with or without subsequent tooth extraction, responded to ATP. In the 10 responders, VAS scores for spontaneous pain decreased slowly but progressively during the infusion period, and eventually, ATP reduced the VAS scores for spontaneous pain and allodynia by 82 +/- 15% and 74 +/- 9%, respectively. In these responders, the analgesic and anti-allodynic effects of ATP outlasted the infusion period for medians of 7 and 12 h, respectively.
  
  
  CONCLUSIONS
  Intravenous ATP did not relieve non-neuropathic orofacial pain. However, it exerted slowly expressed but long-lasting analgesic and anti-allodynic effects in patients with neuropathic orofacial pain, especially in those suffering from neuropathic pain following pulpectomy and/or tooth extraction.
authors.affiliation: Department of Dental Anesthesia and Orofacial Pain Center, Tokyo Dental College, Suidoubashi Hospital, 2-9-18 Misaki-cho, Chiyoda-ku, Tokyo, 101-0061, Japan.
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Fukuda
authors.forename: Masakazu
authors.initials: M
authors.lastname: Hayashida
authors.forename: Atsuo
authors.initials: A
authors.lastname: Fukunaga
authors.forename: Masataka
authors.initials: M
authors.lastname: Kasahara
authors.forename: Yoshihiko
authors.initials: Y
authors.lastname: Koukita
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ichinohe
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Kaneko
mesh_terms: D000255:Adenosine Triphosphate / Q000008:administration & dosage / Q000627:therapeutic use*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000700:Analgesics / Q000627:therapeutic use; D000704:Analysis of Variance; D001794:Blood Pressure / Q000187:drug effects; D004562:Electrocardiography / Q000379:methods; D005157:Facial Pain / Q000188:drug therapy* / Q000209:etiology; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D007552:Isotonic Solutions / Q000008:administration & dosage; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods; D010092:Oximetry / Q000379:methods; D010147:Pain Measurement / Q000379:methods; D010148:Intractable Pain / Q000188:drug therapy* / Q000209:etiology; D011670:Pulpectomy / Q000009:adverse effects; D000077331:Ringer's Solution; D012720:Severity of Illness Index; D013997:Time Factors; D014081:Tooth Extraction / Q000009:adverse effects
chemical_list: D000700:Analgesics; D007552:Isotonic Solutions; D000077331:Ringer's Solution; D000255:Adenosine Triphosphate