Patients with recent or anticipated neuraxial anesthesia (epidural or spinal anesthesia) are at risk of spinal or epidural hematoma and subsequent paralysis. Use with extreme caution in patients with increased risk of hemorrhage (with bacterial endocarditis, congenital or acquired bleeding disorders, active ulceration and angiodysplastic GI disease, hemorrhagic stroke, or recent brain, spinal, or ophthalmologic surgery). Increased risk for hemorrhage in patients treated concomitantly with platelet inhibitors. Use with caution in bleeding diathesis, uncontrolled arterial hypertension, or history of recent GI ulceration, diabetic retinopathy, or hemorrhage. Risk of bleeding may be increased in low weight patients. Cases of heparin-induced thrombocytopenia with thrombosis reported, including complications such as organ infarction, limb ischemia, or death. Use with extreme caution in history of heparin-induced thrombocytopenia and also in congenital or drug-induced thrombocytopenia or platelet defects. Heparin can cause hyperkalemia by affecting aldosterone; similar reactions could occur with LMWHs. Not recommended for thromboprophylaxis in prosthetic heart valves (especially pregnant women). Use with caution in renal failure. Use with caution in the elderly. Multidose vials contain benzyl alcohol and should not be used in pregnant women. In neonates, large amounts of benzyl alcohol (>100 mg/kg/day) have been associated with fatal toxicity («gasping syndrome»). Do not administer I.M.. Not to be used interchangeably (unit for unit) with heparin or any other LMWHs.