title: Acute auditory and vestibular symptoms associated with heat and transdermal lidocaine.
abstract: OBJECTIVE
  To describe a case of systemic lidocaine toxicity from the simultaneous use of transdermal patches and a heating pad.
  
  
  METHODS
  Case report and discussion.
  
  
  RESULTS
  The focus of this case report are the interesting neuro-otologic signs of central lidocaine toxicity that occurred after a patient fell asleep on a heating pad with his Lidoderm patches in place. Hearing improvement, tinnitus reduction, and severe dizziness and ataxia were present for approximately 48 hours before spontaneous resolution. Based upon his symptoms we estimate an 11-fold increase in plasma concentrations of lidocaine.
  
  
  CONCLUSIONS
  Transdermal delivery of medication affords ease of application, ability to provide continuous pharmacological therapy, and ability to supply medication to the affected site. Due to the superficial application of these medications, external environmental factors may influence the pharmacokinetics of drug delivery. This case highlights the complications that can arise from the combination of heating pads and transdermal pain therapies.
authors.affiliation: Department of Otolaryngology and Communication Sciences, Medical College of Wisconsin, 9200 West Wisconsin Avenue, Milwaukee, WI 53226, USA.
authors.forename: Nima
authors.initials: N
authors.lastname: Shemirani
authors.forename: Darryl
authors.initials: D
authors.lastname: Tang
authors.forename: David R
authors.initials: DR
authors.lastname: Friedland
mesh_terms: D000279:Administration, Cutaneous; D000368:Aged; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000009:adverse effects*; D001304:Auditory Diseases, Central / Q000139:chemically induced*; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008012:Lidocaine / Q000008:administration & dosage / Q000009:adverse effects*; D008297:Male; D010147:Pain Measurement / Q000379:methods; D015837:Vestibular Diseases / Q000139:chemically induced*
chemical_list: D000779:Anesthetics, Local; D008012:Lidocaine