Haematology reference guide for Dalteparin dose recommendations for treatment of venous thromboembolism (VTE) in adult patients with obesity

 

Please note:

  • This guide is not intended for paediatric use
  • Recommendations for dosing in pregnancy and the puerperium are given in RCOG Greentop 57a and differ from non-pregnant adults due to differences in the volume of distribution of Dalteparin in pregnancy

Disclaimer

  • Our aim is to guide members of the haematology department if asked to give advice for patients with VTE that require immediate anticoagulation
  • This document should not be used without consulting with haematology
  • The doses quoted are off-label

 

Background

The manufacturers of Dalteparin recommend a capped dose of 18,000 units subcutaneously daily for patients with body weight >83 kg, yet other low molecular weight heparin (LMWH) brands such as Enoxaparin and Tinzaparin recommend non-capped weight-based dosing in obese patients.

In NHS England some Exemplar centres are advising a similar weight-based dosing approach for Dalteparin for patients with body weight >120 kg and the suggested doses are given in Tables 1.4 and 1.5. These doses are off-label and are intended to be used by haematology only to recommend starting doses of Dalteparin when clinical situations arise, for example a patient with a life[1]threatening acute venous thrombosis, when immediate full anticoagulation is necessary. It is advised that LMWH anti-Xa monitoring is performed to monitor the response in this setting. In general, this approach should not be used in the peri-operative setting, when the manufacturer's recommended capped dose should be given, but this is at the discretion of the advising and attending clinicians.

 

How to arrange a LMWH level

LMWH anti-Xa levels are ordered on TRAK as "heparin assay" and click on LMWH; samples are sent in a green citrated tube filled adequately to the level marked on the tube. Samples must be couriered to the RIE haematology laboratory if the patient is being managed at other NHS Lothian sites. A 24-hour service is available for this automated test and all requests should be discussed with the duty laboratory haematology biomedical scientist (laboratory): extension 26093 or page 6550/via switchboard out of hours.

 

When to take a LMWH level

A peak LMWH anti-Xa level should be taken after the third dose of LMWH has been administered, and taken 3-4 hours following the administration of the drug.

Interpretation:

For patients on once daily dosing, the expected peak plasma concentration is about 1.0 anti-Xa unit per mL with a range of 0.5 to 1.5 (and 0.5 to 1.0 anti-Xa units per mL for twice daily dosing). The duty haematologist can assist with dose adjustment if the level is subtherapeutic, low or supratherapeutic.

 

Suggested starting doses of Dalteparin in patients with obesity and CrCl greater than 30ml/min

 

Weight (kg) Suggested starting dose by subcutaneous injection
83-120 18,000 units daily
121-131 12,500 units twice daily
132-143 15,000 units morning & 12,500 units evening
144-157 15,000 units twice daily
158-172 18,000 units morning & 15,000 units evening
Over 172 18,000 units twice daily

Single doses should not exceed 18,000 units

 

Suggested starting doses of Dalteparin in patients with obesity and CrCl less than 30ml/min*

 

Weight (kg) Suggested starting dose by subcutaneous injection
83-120 12,500 units daily
121-133 10,000 units morning & 7,500 units evening
134-151 10,000 units twice daily
152-168 12,500 units morning & 10,000 units evening
Over 169 12,500 units twice daily

*The use of CrCl is preferred over eGFR in obese patients with renal impairment. Creatinine clearance could be calculated by using the CrCl calculator on the Intranet (see link below).

http://intranet.lothian.scot.nhs.uk/Pages/Search-Results.aspx?k=creatinine%20clearance%20calculator

 

Alternative option

The alternative is to use intravenous (IV) unfractionated heparin (UFH) and monitor the APTT appropriately.

  • The advantage of UFH is that it can be easily stopped if necessary and its effects wear off rapidly. It can also be easily reversed with protamine.
  • The disadvantage is that achieving adequate anticoagulation is unpredictable and dosage adjustments based on appropriately timed APTT measurements require careful management. Venous access may also be problematic in patients with obesity.

 

Editorial Information

Last reviewed: 20/04/2020

Author(s): J Anderson R Ganchev.

Version: 1.0

Approved By: Drugs and Therapeutics Committee