Prescribing enoxaparin

• No routine monitoring of anticoagulant effect is required for enoxaparin. Dosing adjustments are required for patients with CrCl < 30 ml/min or weighing 130kg or more (see ‘Recommended doses’ below).
• 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.

• within 12 hours of an invasive procedure e.g. surgery/epidural
• platelets <50x10⁹/L (see guidance below on thrombocytopenia)
• 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

Enoxaparin 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).

Patients should receive a minimum of 3 months enoxaparin before reassessment of their risk factors. If the patient’s cancer is not cured, or they continue to receive SACT, continuing anticoagulation to complete 6 months is recommended. For patients with active cancer or continuing SACT treatment 6 months post-clot diagnosis, 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 injections.   

Dosing recommendations

• The two treatment tables below outline the treatment for VTE with enoxaparin guided by the indications, weight and creatinine clearance.
• The dosing schedule for initial treatment of cancer-associated VTE requiring LMWH is 1mg/kg TWICE daily for 5 days (TABLE 2), then revert to 1.5mg/kg ONCE daily (TABLE 1)
• For treatment of non-high risk VTE with CrCl ≥30ml/min, this is based on a dose of 1.5mg/kg ONCE daily. (TABLE 1)
• For treatment of high-risk VTE, this is based on a dose of 1mg/kg TWICE daily (TABLE 2)
• For patients with CrCl <30 ml/min regardless of non-high risk or high risk, the dose is based on 1mg/kg ONCE daily.
• For patients who weigh ≥130kg, the dose is based on 0.85mg/kg TWICE daily.
• Patients with CrCl <30ml/min and/or weigh ≥130kg should have Anti-Xa levels monitored(*) - please see section below for monitoring details.

Twice daily enoxaparin at 1mg/kg (Refer to table 2)  should be used for patients with CrCl >30ml/min who meet any of the following criteria:

• High risk VTE:
  • Iliac vein DVT
  • Symptomatic PE- those not suitable for a DOAC
  • Initial treatment of cancer-associated VTE requiring LMWH for 5 days, then to revert to the treatment table 1 below
  • Weight over 130kg
• Short term anticoagulation of arterial thrombosis
• Short term anticoagulation of atrial fibrillation
• Short-term anticoagulation of mechanical valves

Table 1- Enoxaparin dosing for acute VTE  - 1.5mg/kg ONCE daily rounded to nearest syringe size (excluding active cancer or high- risk features)

Table 2- Enoxaparin dosing for high-risk VTE -1mg/kg TWICE daily rounded to nearest syringe size (including initial treatment of VTE in cancer patients (first 5 days treatment then refer to  Table 1) 

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 days. 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 enoxparin dose  requirements for monitoring and who is taking responsibility for this with the GP. A standard GP letter containing essential information can be found on the Cancer Services intranet site (OOQS).