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Anticoagulants · Hematology

Enoxaparin

low molecular weight heparin · Lovenox® · Clexane®(brand names vary by market)

The injectable bridge: predictable, weight-based, and kidney-dependent.

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Illustration of Enoxaparin as a injection

Mechanism

Binds antithrombin and accelerates its inhibition of factor Xa, with less anti-IIa effect than unfractionated heparin. That ratio is what makes the response predictable enough to dose by weight without monitoring.

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Indications

  • Venous thromboembolism, treatment and prophylaxis
  • Acute coronary syndromes
  • Anticoagulation in pregnancy
  • Bridging where an oral agent is unsuitable

Formulations

Injection

Dosing concepts

Weight-based

Treatment dosing is by actual body weight, and both under-dosing in obesity and over-dosing in the very light are common, consequential errors.

Renal impairment

Renally cleared, so it accumulates as clearance falls; below about 30 mL/min the dose is reduced or unfractionated heparin is used instead.

Prophylaxis versus treatment

The two dose bands differ several-fold. Confusing them is one of the highest-harm errors on any surgical ward.

Concepts, not prescribing instructions. Practice numbers live in current references and local protocols.

Pharmacokinetics

Bioavailability
~90% subcutaneously
Half-life
4 to 7 h, considerably longer in renal impairment
Elimination
renal
Protein binding
Low

Does not cross the placenta, which is why it is the anticoagulant of pregnancy.

Play with these concepts in the PK Lab

Adverse effects

  • Bleedingcommon & serious
  • Injection-site bruisingcommon
  • Heparin-induced thrombocytopeniaseriousLess common than with unfractionated heparin but not absent; a falling platelet count between days 5 and 10 is the alarm.
  • Hyperkalemia through aldosterone suppressionserious
  • Osteoporosis with prolonged useserious

Contraindications & precautions

Contraindications

  • Active major bleeding
  • History of heparin-induced thrombocytopenia
  • Neuraxial anaesthesia within the specified window

Precautions

  • Renal impairment
  • Extremes of body weight
  • Recent neurosurgery or spinal procedure

Interactions

Monitoring

Platelet count

To catch heparin-induced thrombocytopenia · Baseline and periodically during therapy

Renal function

Accumulation risk

Anti-Xa level in pregnancy, obesity, or renal impairment

The situations where weight-based dosing stops being predictable

Potassium on prolonged courses

Aldosterone suppression is a genuine and forgotten effect

Counselling points

  • Rotate injection sites around the abdomen; do not rub afterwards.
  • Bruising at the site is expected; widespread bruising is not.
  • Do not expel the air bubble in a prefilled syringe.
  • Report black stools, unusual bleeding, or a nosebleed that will not stop.

Clinical pearls

  • Protamine reverses it only partially, roughly 60 percent of the anti-Xa effect, which is a meaningful difference from unfractionated heparin in a bleeding emergency.
  • The timing rules around spinal and epidural procedures exist because of spinal haematoma, and they are absolute rather than advisory.

References & review

  • Enoxaparin product monograph (consult the current version for your market) (monograph)
  • Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed. (reference-work)

Last reviewed 2026-08-16 · jurisdiction: global · drug information changes; verify against current references before practice use.

Keep going

Anticoagulants →Warfarin →The coagulation cascade →Compare with another agent →