title: Debilitating reaction following the initial dose of tramadol.
abstract: OBJECTIVE
  To describe a debilitating reaction following a single oral dose of tramadol.
  
  
  METHODS
  A 32-year-old white man with no prior medical problems, allergies, or previous medication reactions experienced ataxia, dilation of the pupils, numbness in his arms and legs, tremulousness, and dysphoria lasting approximately 4 hours following an initial tramadol dose (100 mg). The patient recovered with no sequelae.
  
  
  CONCLUSIONS
  Central nervous system (CNS) stimulation during therapy with tramadol was reported in 7% of patients in clinical trials. These reactions are usually mild and transient. This report describes a debilitating CNS-mediated reaction to an initial dose of tramadol in an otherwise healthy adult. The patient was phenotyped for CYP2D6 activity, the major metabolic pathway for tramadol elimination, and was determined to be an extensive metabolizer with very high CYP2D6 activity.
  
  
  CONCLUSIONS
  The exact mechanism of the adverse response is not known; however, based on phenotyping results, we suspect that it may be related to high concentrations of the active O-desmethyl metabolite of tramadol.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, PA 15261, USA.
authors.forename: P P
authors.initials: PP
authors.lastname: Gleason
authors.forename: R F
authors.initials: RF
authors.lastname: Frye
authors.forename: T
authors.initials: T
authors.lastname: O'Toole
mesh_terms: D000328:Adult; D017109:Akathisia, Drug-Induced / Q000209:etiology*; D000701:Analgesics, Opioid / Q000009:adverse effects*; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism; D003647:Debrisoquin / Q000652:urine; D006801:Humans; D008297:Male; D010146:Pain / Q000188:drug therapy*; D010641:Phenotype; D012782:Shoulder; D014147:Tramadol / Q000009:adverse effects* / Q000378:metabolism
chemical_list: D000701:Analgesics, Opioid; D014147:Tramadol; D019389:Cytochrome P-450 CYP2D6; D003647:Debrisoquin