Generic Name

Phenindione

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Classification

FDA Approved Indications

• Prevention and treatment of thromboembolic disorders, such as deep vein thrombosis, pulmonary embolism, and atrial fibrillation-related embolism

Mechanism of Action

Inhibits synthesis of vitamin K-dependent clotting factors II, VII, IX, and X, thereby impairing clot formation

Dosage and Administration

Adult: Typically 100-200 mg daily, divided into doses; dosage adjusted based on INR monitoring

Pediatric: Not commonly used; limited data available, consult specialist

Geriatric: Start with lower doses due to increased bleeding risk; monitor closely

Renal Impairment: Use with caution; dose adjustments may be necessary depending on renal function

Hepatic Impairment: Use with caution; hepatic function affects drug metabolism

Pharmacokinetics

Absorption: Well absorbed orally

Distribution: Widely distributed; crosses placental barrier

Metabolism: Metabolized in the liver by CYP enzymes

Excretion: Excreted primarily in urine

Half Life: Approximately 8-12 hours; varies among individuals

Contraindications

• Known hypersensitivity to phenindione or other vitamin K antagonists
• Active bleeding
• Bleeding disorders

Precautions

• Use with caution in patients with hepatic or renal impairment, bleeding tendencies, or recent surgery
• Monitor INR regularly

Adverse Reactions - Common

• Bleeding (Common)
• Nausea (Less common)
• Vomiting (Less common)

Adverse Reactions - Serious

• Hemorrhage (Serious and requires immediate attention)
• Decresed bone marrow function (Rare)

Drug-Drug Interactions

• Other anticoagulants, antiplatelet agents, NSAIDs, CYP450 inhibitors or inducers

Drug-Food Interactions

• Vitamin K-rich foods (e.g., green leafy vegetables) may reduce efficacy

Drug-Herb Interactions

• Herbal supplements affecting coagulation (e.g., garlic, ginkgo)

Nursing Implications

Patient/Family Teaching

• Take medication exactly as prescribed
• Report signs of bleeding (e.g., unusual bruising, blood in stool or urine)
• Maintain consistent intake of vitamin K-rich foods
• Avoid alcohol and other medications that increase bleeding risk
• Schedule regular INR monitoring appointments

Special Considerations

Black Box Warnings:

• Significant bleeding risk; requires careful monitoring

Genetic Factors: Genetic polymorphisms in CYP2C9 can affect metabolism and dosing

Lab Test Interference: May interfere with certain coagulation assays

Overdose Management

Signs/Symptoms: Excessive bleeding, hematuria, gastrointestinal bleeding

Treatment: Discontinue drug, provide supportive care, administer vitamin K, consider fresh frozen plasma or prothrombin complex concentrates in severe cases

Storage and Handling

Storage: Store at room temperature, away from moisture and sunlight

Stability: Stable for the duration specified on the package; verify expiration date