Letters to the Editor

Treatment of Venous Thromboembolism in Patients Who Are Morbidly Obese


Am Fam Physician. 2018 Apr 15;97(8):497-498.

Original Article: Deep Venous Thrombosis and Pulmonary Embolism: Current Therapy

Issue Date: March 1, 2017

See additional reader comments at: https://www.aafp.org/afp/2017/0301/p295.html

To the Editor: We read the article on venous thromboembolism (VTE) with interest and appreciate that the authors highlight the different treatment options for this disease state. Given the limited data regarding treatment of VTE in patients who are morbidly obese (body mass index [BMI] of 40 kg per m2 or more) and that the current prevalence of morbid obesity in the United States is around 8%,1 family physicians must keep weight and BMI in mind when considering direct oral anticoagulants and low-molecular-weight heparin (LMWH) for VTE treatment.

The International Society on Thrombosis and Haemostasis offers some guidance.2 Standard dosing of direct oral anticoagulants should still be considered for VTE prevention and treatment for patients with a BMI less than or equal to 40 kg per m2 or weight less than or equal to 264 lb (120 kg). For patients with a BMI greater than 40 kg per m2 or weight more than 120 kg, direct oral anticoagulants should not be considered a first-line therapy because of limited clinical data and evidence suggesting decreased exposure, concentration, and half-lives at the weight extremes.

However, the International Society on Thrombosis and Haemostasis suggests that for patients who are morbidly obese who cannot use a vitamin K antagonist (warfarin [Coumadin]), physicians might consider checking anti–factor Xa peak and trough levels (for apixaban [Eliquis], edoxaban [Savaysa], and rivaroxaban [Xarelto]). It should be noted that all data regarding anti– factor Xa levels used tests specifically calibrated for the drug being tested or mass spectrometry drug levels. Continuing the direct oral anticoagulant is reasonable if the level falls within the expected range, but changing to a vitamin K antagonist is recommended, if possible, if the drug level is below the therapeutic range.2

If a vitamin K antagonist and bridging with LMWH is used, it is also important to note the limited data and different pharmacokinetic and pharmacodynamic properties in patients who are morbidly obese. The LMWH agent enoxaparin (Lovenox) has no official dosing recommendations for these patients,3 but data in this population suggest that a reduced weight-based dose (less than 1 mg per kg) is warranted.4,5 A retrospective cohort of 99 patients with BMI greater than 40 kg per m2 or weight more than 331 lb (150 kg) showed that more than 50% of patients had supratherapeutic peak anti–factor Xa levels using normal weight-based dosing of 1 mg per kg of enoxaparin.4 A prospective dosing study also showed an average enoxaparin dose of 0.71 mg per kg for therapeutic effects.5 Therefore, it is also important for physicians to consider starting LMWH at lower doses and consider monitoring peak anti–factor Xa concentrations in patients who are morbidly obese.

Author disclosure: No relevant financial affiliations.


show all references

1. Flegal KM, Kruszon-Moran D, Carroll MD, Fryar CD, Ogden CL. Trends in obesity among adults in the United States, 2005 to 2014. JAMA. 2016;315(21):2284–2291....

2. Martin K, Beyer-Westendorf J, Davidson BL, Huisman MV, Sandset PM, Moll S. Use of the direct oral anticoagulants in obese patients: guidance from the SSC of the ISTH. J Thromb Haemost. 2016;14(6):1308–1313.

3. Lovenox (enoxaparin) [prescribing information]. Bridgewater, N.J.: Sanofi-Aventis; 2013. http://products.sanofi.us/lovenox/lovenox.html. Accessed November 2, 2017.

4. Lee YR, Vega JA, Duong HN, Ballew A. Monitoring enoxaparin with antifactor xa levels in obese patients. Pharmacotherapy. 2015;35(11):1007–1015.

5. Lalama JT, Feeney ME, Vandiver JW, Beavers KD, Walter LN, McClintic JR. Assessing an enoxaparin dosing protocol in morbidly obese patients. J Thromb Thrombolysis. 2015;39(4):516–521.

In Reply: We thank Drs. Gibbs and Sheley for raising an important issue regarding our article. We agree that direct oral anticoagulant use in patients with a BMI greater than 40 kg per m2 has not been adequately studied and should be avoided. Although monitoring peaks and troughs in anti–factor Xa levels in patients who are morbidly obese and treated with factor Xa inhibitors may help safely guide therapy in this population, these laboratory assays are not readily available to most family physicians. In our experience, treatment of acute VTE in patients who are morbidly obese is most safely achieved by using intravenous unfractionated heparin and concomitant warfarin.

Author disclosure: No relevant financial affiliations.

Send letters to afplet@aafp.org, or 11400 Tomahawk Creek Pkwy., Leawood, KS 66211-2680. Include your complete address, e-mail address, and telephone number. Letters should be fewer than 400 words and limited to six references, one table or figure, and three authors.

Letters submitted for publication in AFP must not be submitted to any other publication. Possible conflicts of interest must be disclosed at time of submission. Submission of a letter will be construed as granting the AAFP permission to publish the letter in any of its publications in any form. The editors may edit letters to meet style and space requirements.

This series is coordinated by Kenny Lin, MD, MPH, Associate Deputy Editor for AFP Online.



Copyright © 2018 by the American Academy of Family Physicians.
This content is owned by the AAFP. A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. This material may not otherwise be downloaded, copied, printed, stored, transmitted or reproduced in any medium, whether now known or later invented, except as authorized in writing by the AAFP. Contact afpserv@aafp.org for copyright questions and/or permission requests.

Want to use this article elsewhere? Get Permissions


Sep 2021

Access the latest issue of American Family Physician

Read the Issue

Email Alerts

Don't miss a single issue. Sign up for the free AFP email table of contents.

Sign Up Now

Navigate this Article