title: Comparison of bivalirudin dosing strategies using total, adjusted, and ideal body weights in obese patients with heparin-induced thrombocytopenia.
abstract: OBJECTIVE
  To compare dosing strategies using total body weight (actual measured body weight), adjusted body weight, and ideal body weight when starting bivalirudin for the treatment for heparin-induced thrombocytopenia (HIT) in obese patients, and to compare differences in dosing requirements and clinical outcomes between obese and nonobese patients.
  
  
  METHODS
  Retrospective medical record review.
  
  
  METHODS
  Academic tertiary care medical center.
  
  
  METHODS
  One hundred thirty-five medical and surgical patients who were treated with bivalirudin for HIT between June 1, 2004, and October 1, 2009.
  
  
  RESULTS
  The 135 patients were separated into two groups based on body mass index (BMI): 46 patients had a BMI greater than 30 kg/m(2)  and were classified in the obese group; the nonobese group consisted of 89 patients with a BMI less than 30 kg/m(2) . The mean BMI in the obese group was 37.7 kg/m(2)  (range: 30.1-56.2 kg/m(2) ). Weight-standardized doses that achieved activated partial thromboplastin time (aPTT) goal were compared in the obese group. The mean ± SD doses that achieved aPTT goal with total (actual), adjusted, and ideal body weights in this group were 0.1 ± 0.07, 0.11 ± 0.08, and 0.14 ± 0.09 mg/kg/hour, respectively. Of the three weight-based dosing approaches, total body weight followed by adjusted body weight provided the closest correlation to rates observed at the target aPTT goal. The secondary analysis compared initial doses of bivalirudin, doses required to reach goal aPTT, time to achieve goal aPTT, and clinical outcomes (number of patients not achieving goal, new thrombosis, major bleeding, and 30-day all-cause mortality) between the obese and nonobese groups. A significant difference in initial dose was noted between groups; however, no significant differences in dose required to achieve goal aPTT, time to achieve goal aPTT, and clinical outcomes were noted between the obese and nonobese groups.
  
  
  CONCLUSIONS
  This study provides evidence that the dosing strategy for bivalirudin based on total body weight is the most accurate predictor of achieving aPTT goal in obese patients with HIT. The study also suggests that there are no clinical differences that warrant different dosing strategies between obese and nonobese patients. Further prospective studies are needed to confirm these findings.
authors.affiliation: Department of Pharmaceutical Services, University of California Davis Medical Center, Sacramento, California 95817-2201, USA.
authors.forename: Laura V
authors.initials: LV
authors.lastname: Tsu
authors.forename: William E
authors.initials: WE
authors.lastname: Dager
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D001835:Body Weight / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D005260:Female; D006493:Heparin / Q000009:adverse effects* / Q000097:blood; D006629:Hirudins / Q000008:administration & dosage* / Q000097:blood; D006801:Humans; D056865:Ideal Body Weight / Q000187:drug effects*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000188:drug therapy*; D010314:Partial Thromboplastin Time; D010446:Peptide Fragments / Q000008:administration & dosage* / Q000097:blood; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000097:blood; D012189:Retrospective Studies; D013921:Thrombocytopenia / Q000097:blood / Q000139:chemically induced* / Q000188:drug therapy; D055815:Young Adult
chemical_list: D006629:Hirudins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D006493:Heparin; C074619:bivalirudin