Drug therapy / treatment options for the management of PE / DVT

This section does not cover drug therapy and treatment of PE / DVT in pregnancy.  See separate GGC Thromboembolic Disease in Pregnancy and the Puerperium guideline for treatment in pregnant patients.

Guidance in this section covers: 

• Subcutaneous low molecular weight heparin (LMWH) 
• Unfractionated heparin 
• Direct oral anticoagulants (DOACs)
• Warfarin 

It may be useful to refer back to the following pages: 

• Diagnosis and treatment of venous thromboembolism (VTE)
• Investigation and management of Deep Vein Thrombosis 
• Investigation and management of Pulmonary Embolism 

Subcutaneous LMWH

Dalteparin is the LMWH currently used for the initial treatment of VTE, unless the patient has specific contraindications to it, or is to be treated with apixaban initially.

Continue with dalteparin until:

• The diagnosis is disproved or
• The diagnosis is confirmed and either apixaban (or another direct oral anticoagulant) is commenced, or dalteparin has been over-lapped with warfarin for at least 5 days and the INR has been ≥2 for two consecutive days. 

Dalteparin does not require laboratory monitoring (APTT is inappropriate, though if significant renal impairment or exceptionally low or high body weight, consider assessing anti-factor Xa activity after 3 consecutive doses of dalteparin, at 4 hours post dose (when target would be 0.5–1.2units/ml)). 

Dalteparin

Dose is 200units/kg subcutaneously once daily with 18,000units the maximum recommended daily dose.

Table 1 – Dalteparin dosing

NOTES

• NHSGGC guidance on Heparin Dose Adjustment at Extremes of Body weight and with Heparin Dose Adjustment in Renal Impairment (CrCl <30ml/minute) are available on the Clinical Guidelines Platform.
• In patients with a high bleeding disorder risk, consider dividing into twice daily dosing.

Unfractionated Heparin (Heparin Sodium)

• Used in the treatment of DVT / PE if rapid anticoagulation is deemed appropriate (e.g. massive PE) or patients thought to be at particularly high bleeding risk (e.g. recent surgery / trauma)
• There are different concentrations of unfractionated heparin currently available – only the 1000units/ml preparation should be used at all times
• Loading Dose: 5,000units by IV bolus over 5 minutes (if 50kg - 100kg*) – use one 5ml vial of 1000units/ml (total concentration 5000units/5ml)
• Maintenance Infusion: 18units/kg/hour (if <100kg*) which is usually ∼1,200units (1.2ml) per hour for a 70kg patient. If patient is at high risk of bleeding, start at 1000units/hour. Use one 20ml vial of 1000units/ml (total concentration 20,000units/20ml). Replace the syringe at least every 24 hours, until treatment is discontinued.
• Monitoring – Check APTT ratio after 6 hours and 4 hours after any change in infusion rate, then daily.
• Adjust infusion rate according to APTT ratio (see table 2 below).

*Note: If <50kg or >100kg - see GGC guideline for heparin dosing details.

Table 2 – Unfractionated heparin dose adjustment

NOTES

• Monitoring - check APTT ratio 4 hours after any change in infusion rate.
• Rarely should patients require infusion rates >1.6–2ml/hour. If target APTT ratio of 1.8–2.8 is not being achieved with a dose of 1.6ml/hour, then monitor anti-factor Xa level (target 0.35–0.7units/ml).
• Routine platelet count monitoring for Heparin Induced Thrombocytopenia is not required unless unfractionated heparin is being administered within 3 months of recent surgery.

Direct Oral Anticoagulants (DOACs)

Apixaban is currently the NHSGGC preferred DOAC for acute treatment and long-term secondary prevention of DVT and/or PE. Rivaroxaban and dabigatran remain on formulary as an option for acute treatment of DVT and/or PE in patients where these drugs are thought to be preferable.

Apixaban and rivaroxaban are oral direct factor Xa inhibitors and dabigatran is an oral direct factor IIa inhibitor. All three have shown to be as effective as LMWH, followed by warfarin, in the treatment of acute PE and/or DVT. No monitoring of the anticoagulant effect of any of these medications is required. Reversal agents are available for apixaban and rivaroxaban (Andexanet Alfa, Ondexxya^®), and dabigatran (idarucizumab, Praxbind^®), see here for more information.

Patients with acute PE and/or DVT deemed suitable for apixaban therapy

• Used after treatment with LMWH (dalteparin) once the diagnosis has been objectively confirmed. Initial treatment with apixaban can be considered if patient is being managed in ambulatory care.
• Apixaban is not recommended if CrCl is <15ml/minute, and should be used with caution if CrCl is 15–29ml/minute.
• Start apixaban 22–24 hours after the last dose of dalteparin.
• Give a loading dose of apixaban* oral 10mg twice daily for the first 7 days and then 5mg twice daily for the remaining duration of acute treatment (i.e. 3 or 6 months).
• If for long-term anticoagulation, the dose of apixaban should be reduced to 2.5mg twice daily after 3-6 months.

*Note: If switching to apixaban after the patient has received a minimum of 7 days of therapeutic LMWH dose, then commence on apixaban oral 5mg twice daily (no loading dose is required). If less than 7 days of therapeutic LMWH dose has been given, then commence on apixaban loading dose for 7 days then the reduced dose as detailed above. 

Exclusion for apixaban treatment 

• Creatinine clearance <15ml/minute
• Liver disease associated with cirrhosis or coagulopathy
• Pregnancy or breast feeding
• Concurrent therapy with azole anti-fungal agents (except for fluconazole), protease inhibitors or strong CYP3A4 inducers (e.g. rifampicin, phenytoin, carbamazepine, phenobarbital or St John's Wort)
• Patients perceived to be at high bleeding risk who would not be suitable for any therapeutic anticoagulant therapy.
• Not recommended in patients weighing >150kg due to lack of evidence.

Patients being discharged on apixaban

• The initial 21 days of treatment (56 x 5mg tablets: 10mg twice daily for 7 days followed by 5mg twice daily for 2 weeks) should be provided from the hospital pharmacy.
• Patients on apixaban do not require referral to an anticoagulant clinic.
• The immediate discharge letter (IDL) should contain clear written information for the GP regarding the duration of treatment and any secondary care follow up.
• Any patient commenced on apixaban should be issued with an apixaban Patient Alert card and offered counselling about this anticoagulant medication.

Warfarin

• Used as follow-on from LMWH in the treatment of DVT and PE for patients not suitable for a DOAC.
• Excluded in pregnant patients, patients who inject drugs and cancer patients.
• Induction treatment with warfarin should always follow a validated induction dosing algorithm suitable to the patient and be accompanied by INR testing on the specified days.
• The age-adjusted Fennerty regimen algorithm (see Warfarin Induction for Inpatients) is suitable for most inpatients who need to quickly achieve a therapeutic INR of 2–3. Daily INR testing is required with this algorithm.
• The protocol gives dosing advice for the first 4 days of warfarin initiation only. From day 5 onwards, dosing should be based on clinical assessment and judgement.
• The use of alternative 'slower' induction regimens (with less intense monitoring) should be considered in outpatients and the elderly (see Warfarin Induction for Outpatients).
• Warfarin should be administered orally, once daily at 6pm.
• All patients must be referred to GCAS (Glasgow and Clyde Anticoagulation Service) via TrakCare referral. 
• Any patient commenced on warfarin should be issued with a yellow anticoagulant booklet and offered counselling about the medication.

Guideline reviewed: March 2026

Page updated: April 2026