Evaluation of an Unfractionated Heparin Pharmacy Dosing Protocol for the Treatment of Venous Thromboembolism in Nonobese, Obese, and Severely Obese Patients

Ann Pharmacother. 2017 Sep;51(9):768-773. doi: 10.1177/1060028017709819. Epub 2017 May 16.


Background: Despite large interpatient variability in dose response, heparin is utilized for treatment of venous thromboembolism (VTE). Current data on the optimal heparin dosing in obese patients are conflicting.

Objective: The objective was to evaluate the time and dose required to achieve a therapeutic activated partial thromboplastin time (aPTT) in nonobese, obese, and severely obese patients using a pharmacist-directed heparin dosing protocol.

Methods: This was a retrospective cohort study in a single-center community hospital inpatient setting. Adult patients receiving heparin for VTE treatment from July 1, 2013, to July 31, 2015, were evaluated. Patients were categorized into 3 groups: nonobese (BMI < 30 kg/m2), obese (BMI = 30-39.9 kg/m2), and severely obese (BMI ≥ 40 kg/m2). Data on height, weight, initial bolus dose, initial infusion rate, time to therapeutic aPTT, and therapeutic infusion rate were collected. Dosing body weight (DBW) was utilized for patients 20% over their ideal body weight (IBW). The primary outcome was time to therapeutic aPTT.

Results: Analysis included 298 patients. Median times to therapeutic aPTT (hours:minutes) in the nonobese, obese, and severely obese were 15:00 (interquartile range [IQR] = 8:05-23:21), 15:40 (IQR = 9:22-25:10), and 15:22 (IQR = 7.54-23:40), respectively ( P = 0.506). There was no difference in bleeding among the nonobese (14%), obese (13.9%), or severely obese groups (7.9%; P = 0.453). No adverse thrombotic events occurred during hospitalization.

Conclusion: Using a DBW for heparin dosing in patients 20% over their IBW resulted in similar times to therapeutic aPTT and adverse events in the nonobese, obese, and severely obese.

Keywords: heparin; obesity; severely obese; venous thromboembolism.

MeSH terms

  • Adult
  • Aged
  • Anticoagulants / administration & dosage*
  • Anticoagulants / therapeutic use
  • Body Weight
  • Dose-Response Relationship, Drug
  • Drug Dosage Calculations*
  • Drug Monitoring
  • Female
  • Heparin / administration & dosage*
  • Heparin / therapeutic use
  • Hospitals, Community
  • Humans
  • Infusions, Intravenous
  • Male
  • Middle Aged
  • Obesity / complications*
  • Obesity / drug therapy
  • Partial Thromboplastin Time
  • Pharmaceutical Services
  • Retrospective Studies
  • Venous Thromboembolism / complications
  • Venous Thromboembolism / drug therapy*


  • Anticoagulants
  • Heparin