Approximately 30% of patients with an episode of adequately treated deep venousthrombosis (DVT) develop post-thrombotic syndrome (PTS) within 2 years. Studieshave shown that the average patient treated with warfarin spends only 60% of thetime in his or her goal international normalized ratio (INR) range of 2.0 to 3.0. A recentinvestigation of the relationship between subtherapeutic INRs and PTS demonstratedthat patients who spent more than 50% of their time below an INR of 2.0 had analmost 3-fold risk of developing PTS. Patients in this study were treated with warfarinfor at least 3 months and were followed for a maximum of 5 years to assess for signs,symptoms, and severity of PTS.
The authors concluded that low-quality treatment with warfarin is related to theoccurrence of PTS in patients with DVT. Strategies aimed at improving the qualityof long-term anticoagulation may have the potential to reduce the incidence of thiscomplication.
Dr. Garrett is a clinical pharmacist practitionerat Cornerstone Health Care in HighPoint, NC.