title: Amitriptyline or not, that is the question: pharmacogenetic testing of CYP2D6 and CYP2C19 identifies patients with low or high risk for side effects in amitriptyline therapy.
abstract: BACKGROUND
  Amitriptyline has been replaced in many countries by alternative and more expensive drugs based on claims of improved tolerability and toxicity and despite slightly reduced efficacy. Preliminary studies indicate that adverse effects could be linked to polymorphisms of drug-metabolizing enzymes, but information on their clinical impact remains scanty and includes mainly case reports. We conducted a prospective blinded two-center study seeking correlations between CYP2C19 and CYP2D6 genotypes, drug concentrations, adverse events, and therapy response.
  
  
  METHODS
  Fifty Caucasian inpatients with at least medium-grade depressive disorder received amitriptyline at a fixed dose of 75 mg twice a day. Blood samples for concentration monitoring of amitriptyline and nortriptyline were taken weekly until discharge along with evaluations of depression (Hamilton Depression Scale and Clinical Global Impression Scale) and side effect (Dosage Record and Treatment Emergent Symptoms Scale; DOTES) scores.
  
  
  RESULTS
  In a ROC analysis, nortriptyline but not amitriptyline concentrations correlated with side effects (DOTES sum score >or=5; area under the curve, 0.733; P = 0.008). Carriers of two functional CYP2D6 alleles had a significantly lower risk of side effects than carriers of only one functional allele (12.1% vs 76.5%; P = 0.00001). The lowest risk was observed for carriers of two functional CYP2D6 alleles combined with only one functional CYP2C19 allele [0 of 13 (0%) vs 9 of 11 (81.8%) for the high-risk group; P = 0.00004]. We found no correlations between drug concentrations or genotypes and therapeutic response.
  
  
  CONCLUSIONS
  Combined pharmacogenetic testing for CYP2D6 and CYP2C19 identifies patients with low risk for side effects in amitriptyline therapy and could possibly be used to individualize antidepressive regimens and reduce treatment cost. Identification of genotypes associated with slightly reduced intermediate metabolism may be more important than currently anticipated. It could also be the key to demonstrating cost-effectiveness for CYP2D6 genotyping in critical dose drugs.
authors.affiliation: Institut für Klinische Chemie und Pathobiochemie, Klinikum rechts der Isar, Technische Universität München, Munich, Germany. W.Steimer@gmx.de
authors.forename: Werner
authors.initials: W
authors.lastname: Steimer
authors.forename: Konstanze
authors.initials: K
authors.lastname: Zöpf
authors.forename: Silvia
authors.initials: S
authors.lastname: von Amelunxen
authors.forename: Herbert
authors.initials: H
authors.lastname: Pfeiffer
authors.forename: Julia
authors.initials: J
authors.lastname: Bachofer
authors.forename: Johannes
authors.initials: J
authors.lastname: Popp
authors.forename: Barbara
authors.initials: B
authors.lastname: Messner
authors.forename: Werner
authors.initials: W
authors.lastname: Kissling
authors.forename: Stefan
authors.initials: S
authors.lastname: Leucht
mesh_terms: D000328:Adult; D000368:Aged; D000639:Amitriptyline / Q000009:adverse effects* / Q000097:blood / Q000627:therapeutic use; D000929:Antidepressive Agents, Tricyclic / Q000009:adverse effects* / Q000097:blood / Q000627:therapeutic use; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D065731:Cytochrome P-450 CYP2C19; D019389:Cytochrome P-450 CYP2D6 / Q000235:genetics*; D003866:Depressive Disorder / Q000188:drug therapy; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D006899:Mixed Function Oxygenases / Q000235:genetics*; D009661:Nortriptyline / Q000097:blood; D010597:Pharmacogenetics; D012372:ROC Curve; D012306:Risk
chemical_list: D000929:Antidepressive Agents, Tricyclic; D000639:Amitriptyline; D009661:Nortriptyline; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19; D019389:Cytochrome P-450 CYP2D6