Phase 1A safety assessment of intravenous amitriptyline.
The antidepressant amitriptyline is used as an adjuvant in the treatment of chronic pain. Among its many actions, amitriptyline blocks Na+ channels and nerves in several animal and human models. As perioperative intravenous lidocaine has been suggested to decrease postoperative pain, amitriptyline, because of its longer half-life time, might be more useful than lidocaine. However, the use of intravenous amitriptyline is not approved by the US Food and Drug Administration. We therefore investigated the adverse effects of preoperative intravenous amitriptyline in a typical phase 1A trial. After obtaining written Food and Drug Administration and institutional review board approval, we obtained written consent for preoperative infusion of amitriptyline in an open-label, dose-escalating design (25, 50, and 100 mg, n=5 per group). Plasma levels of amitriptyline/nortriptyline were determined, and adverse effects were recorded in a predetermined symptom list. Infusion of 25 and 50 mg amitriptyline appears to be well tolerated; however, the study was terminated when 1 subject in the 100-mg group developed severe bradycardia. Intravenous infusion of amitriptyline (25 to 50 mg over 1 hour) did not create side effects beyond dry mouth and drowsiness, or dizziness, in 2 of our 10 otherwise healthy participants receiving the 25- to 50-mg dose. An appropriately powered future trial is necessary to determine a potential role of amitriptyline in decreasing postoperative pain.


CONCLUSIONS
Amitriptyline potently blocks the persistently open Na+ channels, which are known to be instrumental in various pain states. As this occurs at very low plasma concentrations, a single preoperative intravenous infusion of amitriptyline could provide long-lasting pain relief and decrease the incidence of chronic pain.
Fridrich
Peter
P
Trauma Hospital, Lorenz Boehler, Vienna, and Department of Anesthesiology and Critical Care Medicine, Medical University Innsbruck, Austria.
Colvin
Hans Peter
HP
Zizza
Anthony
A
Wasan
Ajay D
AD
Lukanich
Jean
J
Lirk
Philipp
P
Saria
Alois
A
Zernig
Gerald
G
Hamp
Thomas
T
Gerner
Peter
P
D000328:Adult; D000368:Aged; D000639:Amitriptyline / Q000008:administration & dosage* / Q000009:adverse effects* / Q000097:blood; D018712:Analgesics, Non-Narcotic / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood; D001919:Bradycardia / Q000139:chemically induced; D015331:Cohort Studies; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006321:Heart / Q000187:drug effects / Q000502:physiology; D006801:Humans; D007275:Injections, Intravenous / Q000009:adverse effects / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy* / Q000503:physiopathology / Q000517:prevention & control*; D011300:Preoperative Care / Q000379:methods* / Q000706:statistics & numerical data; D012894:Sleep Stages / Q000187:drug effects; D026941:Sodium Channel Blockers / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood; D016896:Treatment Outcome; D014987:Xerostomia / Q000139:chemically induced
D018712:Analgesics, Non-Narcotic; D026941:Sodium Channel Blockers; D000639:Amitriptyline