Perenteral Anticoagulants (FETT)

von Felix C.

Name the category.

Blood Products and Modifiers

Name the main 2 drugs.

Heparin (unfractionated)

ENOXAPARIN

Name an alternative drug.

Tinzaparin

Describe the administration, monitoring during therapy, clearance and antidote for unfractionated heparin (UFH).

Administration
- Prophylaxis: subcutaneous
- Therapeutic: continuous intravenous infusion
Monitoring during therapy: activated partial thromboplastin time (aPTT) , platelet count (including baseline before treatment is started)
Clearance: hepatic (preferred agent for patients with renal insufficiency)
Antidote: protamine sulfate (a positively-charged protein that can neutralize negatively-charged heparin by forming inactive complexes)

Describe the administration, monitoring during therapy, clearance and antidote for low molecular weight heparin (LMWH).

Administration: subcutaneous
Monitoring during therapy: anti-factor Xa activity can be assessed in specific cases; not generally recommended
Clearance: renal (contraindicated for patients with renal insufficiency)
Antidote: protamine sulfate (partial reversal)

Describe the mechanism of action of UFH.

Enhances the activity of antithrombin
Indirect inhibitor of
- Factor Xa: antithrombin III potentiation → inhibition of factor Xa → decreased activation of prothrombin → ↓ thrombin→ ↓ fibrinogen activation → ↓ fibrin
- Thrombin (factor IIa): UFH binds antithrombin III and thrombin simultaneously at two distinct binding sites → antithrombin III and thrombin held by heparin in close proximity (complex formation) → ↑ thrombin inhibition → ↓ fibrinogen activation → ↓ fibrin
Short half-life: anticoagulant effect quickly ceases once administration is stopped

Describe the mechanism of action of LMWH.

Mechanism of action
- LMWH: binds to antithrombin III → inhibition of factor Xa → decreased conversion of prothrombin → ↓ thrombin
- Synthetic heparin: only binds to antithrombin III → selective inhibition of factor Xa
Higher bioavailability than unfractionated heparin
Long half-life: 2–4 times longer than unfractionated heparin

List 2 general side effects.

The significantly increased risk of bleeding is the main side effect of all anticoagulants.

List specific side effects of UFH and LMWH.

Allergic reactions
Heparin-induced thrombocytopenia: risk of type 2 HIT LMWH:UFH ≈ 1:10
Osteoporosis —> Dose-dependent; therefore, switch to oral anticoagulants for long-term therapy. Osteoporosis is most likely related to increased osteoclastic activity, but decreased production of calcitriol is another potential cause.
Drug interactions (e.g., ASA, tetracycline)

Describe the side effect/adverse effect: thrombocytopenia.

Treatment with heparin, especially UFH, can cause thrombocytopenia.
Thrombocytopenia may be immune-mediated heparin-induced thrombocytopenia (formerly known as type 2 HIT) or non-immune heparin associated thrombocytopenia (formerly known as type 1 HIT)

Heparin treatment requires regular monitoring of the platelet count, especially for UFH, even before starting treatment.

List indications for UFH.

Low-dose therapy

DVT prophylaxis for prolonged bedrest, peri- and postoperative state, immobility

High-dose therapy

List indications for LMWH.

List contraindications.

Recent stroke
Uncontrolled hypertension
Active bleeding
HIT (except for direct thrombin inhibitors which can be used for anticoagulation in HIT)

Advantages/Disadvantages table UFH vs. LMWH.

Describe the use of heparin in pregnancy and decreased renal function.

Physiological hypercoagulability (e.g., due to increased levels of clotting factors) leads to increased risk of thrombosis.
UFH and LMWH can be used during pregnancy: neither cross the placenta nor are they transferred through breast milk
LMWH has fewer side effects.

In severe renal failure: accumulation of LMWH → increased bleeding risk → adjust dose or switch to UFH

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