Adult: Initially, 200 mg on day 1 followed by 100 mg on day 2. From day 3, adjust dose according to coagulation tests. Maintenance: 50-150 mg daily (resistant patients may require ≥200 mg daily while sensitive patients may require <50 mg daily). Elderly: Dosage reduction may be needed.
Chống chỉ định
Hypersensitivity. Significant bleeding, haemorrhagic conditions (e.g. haemorrhagic stroke), bacterial endocarditis, uncontrolled HTN; w/in 48 hr postpartum. Severe renal and hepatic impairment. Pregnancy and lactation. Concomitant use of fibrinolytic agents.
Patient w/ risk factors for bleeding (e.g. risk of falling, cerebrovascular disease, serious heart disease, anaemia, malignancy, trauma); genetic variability in relation to VKORC1, recent ischaemic stroke, previous GI bleeding, active peptic ulcers, hyper- or hypothyroidism, acute illnesses; wt loss/gain, protein C or S deficiency, hyperphosphataemia, hypercalcaemia, hypoalbuminaemia. Patient undergoing surgery. Mild to moderate renal impairment. Elderly.
Regularly monitor prothrombin time and assess the need for therapy.
Symptoms: Spontaneous bruising, haematomas, haematuria, rectal bleeding, haemorrhage into any internal organ. Management: Give activated charcoal if ingestion is recent (w/in 1 hr) and ingested amount is >0.25 mg/kg or more than the patient’s therapeutic dose. If prothrombin time is prolonged w/ no active bleeding, give vit K 0.5-1 mg by slow IV infusion. If w/ active bleeding, give fresh frozen plasma and vit K 1 mg by slow IV infusion. If w/ life threatening haemorrhage, give fresh frozen plasma or factor concentrate.
Reduced effects w/ ingestion of food rich in vit K.
Description: Phenindione is an indanedione anticoagulant. It antagonises the effects of vitamin K and interferes w/ the formation of clotting factors II, VII, IX and X. Onset: 36-48 hr. Duration: 48-72 hr. Pharmacokinetics: Absorption: Rapidly and completely absorbed from the GI tract. Time to peak plasma concentration: 1-3 hr. Distribution: Crosses placenta and enters breast milk. Excretion: Via urine (as metabolites).