Nurses Compass
Drug Guide
Phenprocoumon
Classification
Therapeutic: Anticoagulant
Pharmacological: Vitamin K antagonist
FDA Approved Indications
- Prevention and treatment of venous thrombosis, pulmonary embolism, and prevention of thromboembolic complications in atrial fibrillation and prosthetic heart valves
Mechanism of Action
Phenprocoumon inhibits vitamin K epoxide reductase, leading to a decrease in synthesis of vitamin K-dependent clotting factors II, VII, IX, and X, thus exerting an anticoagulant effect.
Dosage and Administration
Adult: Typically 2-8 mg once daily, adjusted based on INR
Pediatric: Not generally recommended; dose individualized if used in rare cases
Geriatric: Start cautiously, with close INR monitoring due to increased bleeding risk
Renal Impairment: Use with caution; no specific dosage adjustments, but monitoring is essential
Hepatic Impairment: Use with caution; dosage adjustments may be necessary, monitoring liver function
Pharmacokinetics
Absorption: Well absorbed orally
Distribution: Widely distributed in body tissues, crosses placenta, appears in breast milk
Metabolism: Hepatic, primarily via CYP450 enzymes
Excretion: Metabolites excreted in urine and bile
Half Life: approximately 5-7 days, enabling once-daily dosing
Contraindications
- Active bleeding
- Severe liver disease
- Known hypersensitivity
Precautions
- Monitor INR regularly, especially during initiation and dose adjustments
- Use with caution in patients with recent surgery, trauma, or high bleeding risk
Adverse Reactions - Common
- Bleeding (Common)
Adverse Reactions - Serious
- Hemorrhage (Serious, requires urgent intervention)
- Hepatotoxicity (Rare)
- Allergic reactions (Rare)
Drug-Drug Interactions
- Other anticoagulants, antiplatelet agents, NSAIDs, certain antibiotics (e.g., macrolides, rifampin), antifungals
Drug-Food Interactions
- Foods high in vitamin K (green leafy vegetables), which can decrease efficacy
Drug-Herb Interactions
- St. John's Wort, ginseng, garlic supplements, which may increase bleeding risk
Nursing Implications
Assessment: Regular INR monitoring, assessment for signs of bleeding or clotting—extremity swelling, chest pain, neurological changes.
Diagnoses:
- Risk for bleeding
- Ineffective tissue perfusion related to bleeding risk
Implementation: Administer at same time daily, educate patient to maintain consistent vitamin K intake, monitor INR frequently.
Evaluation: Maintain INR within therapeutic range, observe for bleeding or thrombosis, adjust dose accordingly.
Patient/Family Teaching
- Take medication at the same time daily.
- Report any unusual bleeding or bruising promptly.
- Maintain a consistent diet with regard to vitamin K intake.
- Inform healthcare providers of all medications and supplements.
Special Considerations
Black Box Warnings:
- Bleeding risk; monitor INR closely
Genetic Factors: Polymorphisms in VKORC1 and CYP2C9 genes can affect dosing
Lab Test Interference: None significant; INR is a reliable measure for monitoring therapy
Overdose Management
Signs/Symptoms: Excessive bleeding, hematuria, hematemesis, melena, petechiae
Treatment: Discontinue drug, administer vitamin K (phytonadione), provide supportive measures including fresh frozen plasma or prothrombin complex concentrates in severe cases.
Storage and Handling
Storage: Store at room temperature, away from moisture and light
Stability: Stable for 2-3 years if stored properly.