What is the immediate treatment for a patient with phlebothrombosis?

The immediate treatment for a patient with phlebothrombosis (deep vein thrombosis or DVT) is anticoagulation therapy. Start with low molecular weight heparin (LMWH) such as enoxaparin 1 mg/kg subcutaneously twice daily or 1.5 mg/kg once daily, or unfractionated heparin as an IV bolus of 80 units/kg followed by continuous infusion at 18 units/kg/hour, adjusted to maintain aPTT at 1.5-2.5 times normal. Simultaneously, begin oral anticoagulation with a direct oral anticoagulant (DOAC) like rivaroxaban (15 mg twice daily for 21 days, then 20 mg once daily) or apixaban (10 mg twice daily for 7 days, then 5 mg twice daily), or warfarin (5-10 mg daily, adjusted to maintain INR 2-3). Elevate the affected limb and provide appropriate pain management. Anticoagulation prevents clot propagation and reduces the risk of pulmonary embolism by inhibiting thrombin formation and factor Xa activity, allowing the body's natural fibrinolytic system to gradually dissolve the existing clot. Treatment duration typically ranges from 3-6 months depending on whether the thrombosis was provoked by a temporary risk factor or is unprovoked/recurrent.