Educational use only. Drug cards are AI-assisted study material for NCLEX preparation.
Mechanism of action
Binds antithrombin III, dramatically accelerating its inactivation of thrombin (factor IIa) and factor Xa. The result is rapid anticoagulation. Given IV for active clots and high-risk indications, or subcutaneously for VTE prophylaxis. Onset is immediate IV, ~1 hour subQ.
Adverse effects
Life-threatening / NCLEX-tested
- Major bleeding — GI, intracranial, retroperitoneal
- Heparin-induced thrombocytopenia (HIT) — paradoxical clotting, occurs ~5–10 days in
- Hyperkalemia (suppresses aldosterone)
- Anaphylaxis (rare)
- Osteoporosis with long-term use
Side effects
Common — what to teach
- Injection-site bruising or hematoma
- Mild thrombocytopenia
- Elevated liver enzymes
- Hair loss with prolonged use
Food & drug interactions
Bleeding risk multiplies with NSAIDs, aspirin, clopidogrel, warfarin, DOACs, and SSRIs. Nitroglycerin IV may reduce heparin effect. Avoid IM injections while anticoagulated — risk of deep hematoma. Do not aspirate or massage subQ injection sites.
Nursing implications
Assessment, monitoring, patient teaching
- Monitor aPTT for IV infusions — therapeutic 1.5–2.5× control (typically 60–80 seconds); titrate per protocol
- Monitor platelet count at baseline and every 2–3 days; a drop > 50% from baseline raises concern for HIT — stop heparin immediately and switch to a non-heparin anticoagulant (argatroban, fondaparinux)
- Antidote is protamine sulfate (1 mg neutralizes ~100 units of heparin)
- Inject subQ deep into abdominal fat, 2 inches from the umbilicus; rotate sites; do not aspirate or rub
- Two-nurse verification for IV heparin doses — high-alert medication
- Watch for signs of bleeding: hematuria, melena, hematemesis, severe headache, petechiae, oozing IV sites
When to hold / contraindications
- aPTT above the therapeutic range per institutional protocol
- Platelet count < 100,000/mm³ or a > 50% drop from baseline (suspect HIT)
- Active major bleeding
- Recent or planned neurosurgery, eye surgery, or lumbar puncture
- Severe uncontrolled hypertension
Memory anchor
"Heparin → aPTT, antidote Protamine. Warfarin → PT/INR, antidote vitamin K." HIT = falling platelets + new clot, ~day 5–10.
Practice Heparin questions
Test your recall on real NCLEX-style pharmacology questions — with full rationales and an AI Coach for the parts you miss.