Prescribing dalteparin

• No routine monitoring of anticoagulant effect is required for dalteparin. Dosing may be unreliable at extremes of weight (BMI ≤19 or BMI ≥40) or in renal impairment (CrCl <30mL/min)
• If symptoms of VTE persist or worsen, or there is evidence of bleeding, LMWH activity can be assessed by testing anti-factor Xa activity around 3-4 hours after a subcutaneous dose of LMWH. 
• Discuss with haematology to arrange anti-Xa assays – it can be ordered on Trak as “LMWH-Heparin assay”.  The target range for therapeutic anticoagulation is 0.5-1.0 anti-Xa units/mL ²².

• within 12 hours of an invasive procedure e.g. surgery/epidural 
• platelets <50x10⁹/L  
• haemorrhagic disorder  
• recent CNS surgery  
• severe liver disease or coagulopathy (PT ratio or APTT ratio >1.5)  
• uncontrolled severe hypertension (BP >180/100mmHg despite treatment)  
• active bleeding site  
• history of HIT.  

Consider risks carefully if cerebral metastases or primary brain tumour.  

Dalteparin should be given by subcutaneous injection, preferably into the abdominal subcutaneous tissue anterolaterally or posterolaterally, or into the lateral part of the thigh. Syringes are non-graduated and for single use only. Doses should be prescribed in full syringes according to the dose banding charts below, and not if CrCl is <30mL/min. Dose should be reduced after first month (and subsequently adjusted if there is significant weight change during treatment)²³.

Patients should receive a minimum of 6 months dalteparin before reassessment of their risk factors. If the patient’s cancer is not cured, or they continue to receive SACT, continuing anticoagulation indefinitely can be considered. However, patients should be re-evaluated frequently to assess risk-benefit ratio of continuing anticoagulant therapy (based on QOL, life expectancy, bleeding risk and preference). If extended anticoagulation is desired, and there are no contraindications, switching to a DOAC may be preferable if a patient does not wish to continue with daily injections⁴.   

• Month 1: dalteparin should be given at a dose of 200units/kg subcutaneously once daily for the first 30 days of treatment.  
• Months 2–6: dalteparin should be given at a dose of 150units/kg subcutaneously once daily for a further 5 months.  

Dalteparin dose bands by weight

All heparins are associated with a (rare) risk of HIT. This usually occurs within the first 14 days of starting heparin. It is associated with a high risk of serious arterial/venous thrombosis and may be life-threatening. Risk of HIT is higher in those who have received heparin within the last 100 days²⁴. Routine FBC monitoring for HIT in cancer patients is not recommended. Exceptions may be made for patients with a high risk of major bleeding (see special circumstances below). 

HIT should be suspected:  

• if the platelet count is found to have fallen by ≥ 30% or if there is unexplained thrombocytopenia (<140 x 10⁹/L) - a clinical assessment as to whether this is likely to be SACT-induced thrombocytopenia should be made for those receiving SACT 
• in patients who develop a new thrombosis or in whom the thrombosis extends  
• if the patient presents with cardiovascular collapse on heparin.

Management of HIT:  

• contact haematology to perform HIT probability screen  
• stop low molecular weight heparin (LMWH) (N.B. do not start alternative anticoagulation instead)
• seek urgent advice from haematology about further investigation and management:  
• refer to the following link: NHS Lothian Guidance on Argatroban for Adult HIT (only accessible when connected to intranet)

It is important to communicate the recommended dalteparin dose (including the requirement for a step-down after one month), requirements for monitoring and who is taking responsibility for this with the GP. There is a standard GP letter containing essential information.