| Class / Target |
Synthetic pentasaccharide; selective factor Xa inhibitor via antithrombin (AT). No thrombin (IIa) activity. |
Heterogeneous heparin fragments; predominant anti-Xa with some anti-IIa activity via AT (agent-specific anti-Xa:anti-IIa ratios). |
| Bioavailability (SC) |
~100% |
~90% (agent-dependent). |
| Onset (SC) |
~2–3 h |
~2–3 h. |
| Half-life |
~17–21 h (renal). |
~4–7 h (renal; enoxaparin ~4.5–7 h; dalteparin/tinzaparin similar). |
| Elimination |
Renal (unchanged) |
Renal (to varying extent); some non-renal clearance. |
| Routine Monitoring |
None (clinical + CBC/platelets). |
None (clinical + CBC/platelets). Anti-Xa in select pts: pregnancy, extremes of weight, renal impairment, pediatrics, high bleed/thrombosis risk. |
| Key Indications |
VTE prophylaxis (surgical/medical); VTE treatment; ACS (UA/NSTEMI; STEMI with fibrinolysis). Off-label HIT treatment/bridging. |
VTE prophylaxis (surgical/medical); VTE treatment; ACS (UA/NSTEMI/STEMI); cancer-associated thrombosis (CAT; particularly dalteparin). |
| Adult Dosing (typical) |
Prophylaxis: 2.5 mg SC once daily (start ≥6–8 h post-op when hemostasis secured). Treatment of VTE: weight-based once daily — 5 mg (<50 kg), 7.5 mg (50–100 kg), 10 mg (>100 kg). ACS: 2.5 mg SC once daily (initial IV 2.5 mg may be used per protocol). |
Enoxaparin: Prophylaxis 40 mg SC daily (orthopedic: 30 mg SC q12h). Treatment VTE 1 mg/kg SC q12h or 1.5 mg/kg daily. ACS 1 mg/kg q12h (STEMI may start with 30 mg IV bolus then SC). Dalteparin: CAT 200 IU/kg daily ×1 mo then 150 IU/kg daily (legacy regimen); VTE treatment ~200 IU/kg daily; prophylaxis 5,000 IU daily. (Adjust per local protocols.) |
| Renal Impairment |
Contraindicated if CrCl <30 mL/min. Use caution 30–50 (consider alternative). No dialysis use. |
Accumulates with reduced CrCl. Enoxaparin: if CrCl <30, reduce to 1 mg/kg daily (treatment) or 30 mg daily (prophylaxis). Others: consider dose ↓/anti-Xa or switch to UFH. Avoid in dialysis; UFH preferred. |
| Hepatic Impairment |
Usually no adjustment; limited data—bleeding risk ↑ in severe disease. |
Usually no adjustment; caution in advanced hepatic disease/coagulopathy. |
| Reversal / Bleeding Management |
No specific antidote. Protamine ineffective. Supportive care ± PCC; consider activated PCC per local policy; dialysis ineffective. |
Protamine partially reverses (≈60% anti-Xa for enoxaparin; better for anti-IIa). Timing-based dosing (e.g., 1 mg protamine per 1 mg enoxaparin if within 8 h; max 50 mg per dose). Residual anti-Xa may persist. |
| HIT Risk / Use in HIT |
Does not bind PF4; extremely low HIT risk. Often used off-label for acute HIT when argatroban/bivalirudin not used. |
Lower HIT risk than UFH but non-zero; can cause/worsen HIT. Contraindicated in active HIT; avoid if HIT within past 100 days unless antibody neg and specialist input. |
| Drug–Drug Interactions |
Pharmacodynamic: ↑ bleeding with antiplatelets, NSAIDs, SSRIs/SNRIs, other anticoagulants, thrombolytics. |
Same class interactions; neuraxial precautions particularly emphasized. |
| Neuraxial Anesthesia |
High spinal/epidural hematoma risk. Typical guidance: avoid while catheter in place; hold 36–42 h before neuraxial procedures; restart ≥6–12 h after catheter removal (confirm local policy). |
Risk present. Typical guidance: prophylactic doses—hold ≥12 h before catheter removal; therapeutic—≥24 h; restart ≥4–6 h after removal (follow local policy/agent PI). |
| Periprocedural Holds |
Low bleed risk: ~24–36 h prior; higher risk or neuraxial: 36–48 h. Resume 6–12 h post-low risk once hemostasis secured (institutional protocols vary). |
Prophylactic dosing: hold 12 h; therapeutic: 24 h (longer if renal impairment/high-risk). Resume 6–12 h if hemostasis secured. |
| Laboratory Effects |
↑ anti-Xa; no effect on aPTT/INR. Can cause mild ↑ in ALT/AST. |
↑ anti-Xa; minimal aPTT effect; no INR effect. Occasional transient LFT elevations. |
| Adverse Effects |
Bleeding; injection-site reactions; anemia; rare hypersensitivity; no HIT expected. |
Bleeding; injection-site hematoma; HIT (rare vs UFH); hyperkalemia (hypoaldosteronism, uncommon); osteoporosis with very prolonged therapy (months). |
| Pregnancy / Lactation |
Limited data; generally avoided unless no alternative (e.g., HIT during pregnancy). |
Anticoagulant of choice in pregnancy (does not cross placenta). Compatible with breastfeeding. |
| Obesity |
Dosed by weight bands; evidence limited at very high weights (>150 kg) → consider anti-Xa or alternative. |
Weight-based dosing (actual body weight). Consider anti-Xa when BMI ≥40 kg/m² or weight >150 kg. |
| Cancer-Associated Thrombosis (CAT) |
Limited data; not first-line. May consider if HIT history. |
Historically standard of care (e.g., dalteparin). Now DOACs often first-line; LMWH preferred when high GI/GU bleed risk, significant drug–drug interactions, or peri-procedural needs. |
| Administration |
SC once daily; abdomen/anterolateral thigh; rotate sites. |
SC once or twice daily; rotate sites. |
| Cost / Access |
Brand-only in many markets; often more expensive. |
Multiple generics (esp. enoxaparin); typically less costly. |
| When I’d Prefer It |
HIT (or high HIT concern); need for once-daily fixed dosing; predictable PK and strong adherence context. |
Pregnancy, CAT, renal function ≥30 with need for weight-based flexibility, peri-procedural plans requiring protamine fallback. |
