Home Drug Guide Warfarin Sodium

Drug Guide

Generic Name

Warfarin Sodium

Brand Names Coumadin, Athrombin, Panwarfin, Jantoven

Classification

Therapeutic: Anticoagulant

Pharmacological: Vitamin K Antagonist

FDA Approved Indications

  • Prevention and treatment of venous thromboembolism (deep vein thrombosis, pulmonary embolism)
  • Atrial fibrillation with embolization risk
  • Mechanical heart valve thromboembolism prevention

Mechanism of Action

Warfarin inhibits hepatic synthesis of vitamin K-dependent clotting factors II, VII, IX, and X, leading to anticoagulation.

Dosage and Administration

Adult: Initial dose usually 2-5 mg daily, adjusted based on INR; maintenance varies.

Pediatric: Use is limited; dosing individualized.

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

Renal Impairment: Adjust dose based on INR; no specific dose reduction common.

Hepatic Impairment: Use with caution; start at lower doses; monitor INR closely.

Pharmacokinetics

Absorption: Well absorbed orally

Distribution: Widely distributed; crosses placenta and enters breast milk

Metabolism: Extensively metabolized in the liver via CYP2C9 and other isoenzymes

Excretion: Metabolites excreted in urine and feces

Half Life: Approximately 20-60 hours (variable)

Contraindications

  • Recent or potential hemorrhagic tendencies
  • Ongoing serious bleeding
  • History of warfarin-induced skin necrosis

Precautions

  • Use with caution in pregnancy (category X), bleeding disorders, uncontrolled hypertension, recent surgery, severe hepatic/renal impairment, alcohol use, elderly, frail patients

Adverse Reactions - Common

  • Bleeding (Very common)
  • Bruising (Common)
  • Nausea or vomiting (Less common)

Adverse Reactions - Serious

  • Hemorrhage (major bleed) (Serious and potentially life-threatening)
  • Purple toe syndrome (Rare)
  • Warfarin-induced skin necrosis (Rare)

Drug-Drug Interactions

  • NSAIDs, antiplatelet agents, other anticoagulants, certain antibiotics (e.g., sulfamethoxazole, metronidazole), amiodarone, phenobarbital

Drug-Food Interactions

  • High intake of vitamin K-rich foods (e.g., leafy greens) can reduce efficacy

Drug-Herb Interactions

  • Ginseng, ginkgo, St. John’s Wort may affect anticoagulation

Nursing Implications

Assessment: Monitor INR regularly; assess for signs of bleeding and thrombosis.

Diagnoses:

  • Risk for bleeding
  • Altered tissue Perfusion

Implementation: Ensure consistent medication timing, monitor INR, educate patient about bleeding precautions.

Evaluation: Maintain INR within therapeutic range, monitor for adverse effects and bleeding

Patient/Family Teaching

  • Take medication exactly as prescribed.
  • Report any bleeding, bruising, or unusual symptoms.
  • Maintain consistent intake of vitamin K-containing foods.
  • Use soft toothbrush and electric razor to prevent bleeding.

Special Considerations

Black Box Warnings:

  • Major or fatal bleeding may occur; use cautiously.

Genetic Factors: CYP2C9 and VKORC1 gene polymorphisms can affect dose requirements.

Lab Test Interference: Warfarin can interfere with some coagulation assays.

Overdose Management

Signs/Symptoms: Excessive bleeding, hematuria, gastrointestinal bleeding, intracranial hemorrhage

Treatment: Administer vitamin K (phytonadione) IV or oral; fresh frozen plasma or prothrombin complex concentrates in severe cases; discontinue warfarin.

Storage and Handling

Storage: Store at room temperature away from moisture and light.

Stability: Stable when stored properly; verify expiration date.

🛡️ 5 Critical Medication Safety Tips for Nurses

1

Triple-Check High-Risk Medications

Always have another nurse verify insulin, heparin, warfarin, and chemotherapy drugs. These "high-alert" medications cause the most serious errors. Check concentration, dose calculation, and pump settings twice.

2

Know Look-Alike, Sound-Alike Drugs

Common mix-ups: hydromorphone/morphine, Celebrex/Celexa, Zyprexa/Zyrtec. Always use BOTH generic and brand names, read labels twice, and use barcode scanning when available. One wrong letter can be fatal.

3

Assess Before AND After Giving Meds

Check vitals before cardiac meds, pain levels before analgesics, and blood glucose before insulin. Always reassess within 30 minutes to evaluate effectiveness and watch for adverse reactions.

4

Watch for Drug Interactions

Common dangerous combinations: warfarin + aspirin (bleeding), ACE inhibitors + potassium (hyperkalemia), digoxin + diuretics (toxicity). Always check drug interactions before administering new medications.

5

Educate Your Patients

Teach patients medication names, purposes, major side effects, and what to report. Informed patients catch errors and improve compliance. Always encourage questions - an educated patient is a safer patient.

⚡ Remember: When in doubt, don't give it out! It's always safer to double-check than regret later.

⚠️ Medical Disclaimer

This drug guide is for educational purposes only and is NOT intended for clinical use. Always consult current prescribing information, healthcare providers, and institutional protocols before administering any medication. Do not use this information for patient care decisions.