Low Molecular Weight Heparin — VTE Prophylaxis Pregnancy: Dalteparin does not pass the placenta; a large amount of data (more than 1000 exposed outcomes) indicate no malformative nor feto/neonatal toxicity, and it can be used during pregnancy if clinically needed, but only if clearly needed as harm cannot be completely ruled out. Epidural anaesthesia during childbirth is absolutely contraindicated in women being treated with high-dose anticoagulants. Preservative-free presentations should be used in pregnancy (multidose vials contain benzyl alcohol). Not recommended in pregnant women with prosthetic heart valves. Breast-feeding: only small amounts of anti-factor Xa activity (2 to 8% of plasma levels) were detected in milk and an anticoagulant effect on the infant appears unlikely, but a risk cannot be excluded.

Dalteparin (Perioperative VTE Prophylaxis)

Brand names: Fragmin

Dalteparin is a low-molecular-weight heparin used for perioperative venous thromboembolism prophylaxis in surgical patients, given by subcutaneous injection.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: DVT prophylaxis in abdominal surgery: 2,500 units subcutaneously once daily, starting 1 to 2 hours prior to surgery and repeated once daily postoperatively. Where abdominal surgery carries a high risk of thromboembolic complications (e.g. malignant disorder): 5,000 units subcutaneously the evening before surgery, then once daily postoperatively; alternatively in patients with malignancy, 2,500 units 1 to 2 hours before surgery followed by 2,500 units 12 hours later, then 5,000 units once daily postoperatively. (Hip replacement regimens - see notes.)

Route: Subcutaneous injection. Do not use as an intramuscular injection; do not mix with other injections or infusions.

Frequency: Once daily (usual duration of administration 5 to 10 days)

SOURCE / INDICATION CAVEAT - the dose above is from the US FDA prescribing information for FRAGMIN (Pfizer, label date 2025-09-30, §2.2), because the fetched UK eMC SPC is for 'Fragmin 10000 IU/0.4ml solution for injection', whose §4.2 covers only TREATMENT of VTE (weight-banded once-daily treatment doses of 7,500 to 18,000 IU, and cancer-associated VTE at 200 units/kg then 150 units/kg) - those are treatment doses and must NOT be used for surgical thromboprophylaxis. The UK SPCs for the Fragmin 2,500 IU and 5,000 IU prefilled syringes, which carry the UK surgical thromboprophylaxis regimens, were not fetched: clinician to source and verify UK doses and timing before use. US label hip replacement surgery regimens (§2.2): postoperative start - 2,500 units 4 to 8 hours after surgery (allowing a minimum of 6 hours before the postoperative day 1 dose), then 5,000 units once daily; preoperative start on the day of surgery - 2,500 units within 2 hours before surgery, then 2,500 units 4 to 8 hours after surgery, then 5,000 units once daily; preoperative start the evening before surgery - 5,000 units, then 5,000 units 4 to 8 hours after surgery, then 5,000 units once daily; usual duration 5 to 10 days after surgery, with up to 14 days well tolerated in clinical trials. Medical patients with severely restricted mobility during acute illness: 5,000 units subcutaneously once daily (usual duration 12 to 14 days in trials). All non-dose fields below (contraindications, interactions, side effects, pregnancy, renal) are taken from the UK eMC SPC unless marked as US label. PAEDIATRIC: the safety and efficacy of dalteparin for PROPHYLAXIS of VTE in children has not been established and no recommendation on a posology can be made (UK SPC §4.2); the per-kg paediatric doses in both labels are for TREATMENT of symptomatic VTE only, so no paediatric prophylaxis dose is given here - verify any paediatric use against a children's formulary. Do not administer by the intramuscular route; avoid intramuscular injection of other preparations when the 24-hour dalteparin dose exceeds 5,000 IU (UK SPC §4.4). Platelet counts should be measured before starting and monitored closely for the first three weeks and regularly thereafter.

Dose adjustments

Renal

UK SPC (stated for treatment dosing): in significant renal failure, defined as a creatinine clearance <30 ml/min, the dose should be adjusted based on anti-Factor Xa activity - if the anti-Factor Xa level is below or above the desired range the dose should be increased or reduced accordingly and the measurement repeated after 3-4 new doses, until the desired level is achieved. No renal dose adjustment for surgical thromboprophylaxis was retrieved - clinician to verify.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Known hypersensitivity to dalteparin or other low molecular weight heparins and/or heparins, e.g. history of confirmed or suspected immunologically mediated heparin induced thrombocytopenia (type II)
Acute gastroduodenal ulcer; cerebral haemorrhage; known haemorrhagic diathesis or other active haemorrhage; serious coagulation disorders
Acute or sub-acute septic endocarditis; haemorrhagic pericardial effusion and haemorrhagic pleural effusion
Injuries to and operations on the central nervous system, eyes and ears
In patients receiving dalteparin for treatment rather than prophylaxis, local and/or regional anaesthesia in elective surgical procedures is contraindicated with high doses of dalteparin
Recent (within 3 months) stroke, unless due to systemic emboli
In cancer patients with body weight <40 kg at the time of the venous thromboembolic event, should not be used for extended treatment of symptomatic VTE and prevention of its recurrence (lack of data)
US label adds: active major bleeding; prior hypersensitivity to heparin or pork products; do not administer to patients undergoing epidural/neuraxial anaesthesia as treatment for unstable angina and non-Q-wave MI, or for prolonged VTE prophylaxis

Side effects

Common: haemorrhage (risk is dose-dependent; most bleeds are mild but severe and fatal bleeding has been reported)
Common: subcutaneous haematoma at the injection site and pain at the injection site
Common: mild thrombocytopenia (type I), usually reversible during treatment; not known - immunologically mediated heparin-induced thrombocytopenia (type II) with or without thrombotic complications
Common: hyperkalaemia (heparin products can cause hypoaldosteronism), and transient elevation of transaminases
Uncommon/rare/not known: hypersensitivity, urticaria, pruritus, skin necrosis, transient alopecia, osteoporosis with long-term treatment, anaphylactic reactions, spinal or epidural haematoma, intracranial and retroperitoneal bleeds (some fatal)

Interactions

Drugs affecting haemostasis - thrombolytic agents, other anticoagulants, NSAIDs, platelet inhibitors or dextran may enhance the anticoagulant effect of dalteparin; concomitant use is not recommended (UK SPC §4.4; US label §7 states oral anticoagulants, platelet inhibitors and thrombolytic agents may increase the risk of bleeding)
Neuraxial (spinal/epidural) anaesthesia or spinal puncture - risk of spinal or epidural haematoma, higher with postoperative indwelling epidural catheters, concomitant drugs affecting haemostasis such as NSAIDs, traumatic or repeated puncture, or a history of spinal surgery or deformity (US label §5.1, boxed warning)
APTT is only moderately prolonged by dalteparin; dose increments based on APTT prolongation may cause overdose and bleeding - APTT should only be used as a test of overdosage (UK SPC §4.4)

Clinical monograph

How it works

It binds antithrombin and accelerates inhibition of factor Xa (with relatively less effect on thrombin), reducing fibrin formation and clot propagation.

Prescribing in practice

Bleeding is the principal risk, so observe strict timing relative to neuraxial (spinal or epidural) anaesthesia and catheter removal to avoid spinal haematoma, and balance prophylaxis timing against surgical bleeding risk.
Reduce the dose and consider anti-Xa monitoring in significant renal impairment, as dalteparin is renally cleared and accumulates.
Monitor for heparin-induced thrombocytopenia and avoid in active major bleeding or known hypersensitivity to heparins.

Monitoring

Monitor platelet count, renal function and for clinical signs of bleeding, using anti-Xa levels only in selected patients such as those with renal impairment.

Counselling the patient

Report any unusual bruising, bleeding or black stools.
Tell the team about any planned spinal or epidural procedure so timing can be managed safely.

Evidence & guidelines

Surgical VTE prophylaxis with low-molecular-weight heparin is supported by NICE NG89 and extensive randomised trial evidence.

Reference: NICE NG89 (VTE Prevention in Hospital); ESRA Guidelines 2021; Fragmin SPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Enoxaparin (Burns — VTE Prophylaxis) · Low Molecular Weight Heparin — VTE Prophylaxis

Pathways