Home Drug Guide Warfarin Potassium

Drug Guide

Generic Name

Warfarin Potassium

Brand Names Athrombin-k

Classification

Therapeutic: Anticoagulant

Pharmacological: Vitamin K Antagonist

FDA Approved Indications

  • Prevention and treatment of venous thromboembolism (deep vein thrombosis, pulmonary embolism)
  • Prevention of stroke and systemic embolism in patients with atrial fibrillation

Mechanism of Action

Warfarin inhibits vitamin K epoxide reductase, leading to decreased synthesis of vitamin K-dependent clotting factors II, VII, IX, and X, thus impairing blood coagulation.

Dosage and Administration

Adult: Dosage varies based on indication; typically, initial dose is 2-5 mg once daily, adjusted based on INR.

Pediatric: Use is limited; dosing is individualized based on INR measurements.

Geriatric: Start at lower end of dosing range due to increased bleeding risk.

Renal Impairment: Adjustments generally not required, but monitor closely.

Hepatic Impairment: Use with caution; hepatic function affects coagulation factors.

Pharmacokinetics

Absorption: Well absorbed orally.

Distribution: Wide distribution; crosses the placenta and is present in breast milk.

Metabolism: Hepatic metabolism mainly via CYP2C9.

Excretion: Metabolites excreted in urine and feces.

Half Life: Approximately 20-60 hours, varies among individuals.

Contraindications

  • Known hypersensitivity to warfarin
  • Active bleeding, including bleeding peptic ulcers
  • Pregnancy (especially during the first trimester)

Precautions

  • Use with caution in hepatic or renal impairment, hypertension, alcoholism, or in elderly patients; monitor INR regularly. Risk of bleeding.

Adverse Reactions - Common

  • Bleeding (Common)
  • Bleeding gums (Common)

Adverse Reactions - Serious

  • Hemorrhage (e.g., intracranial, gastrointestinal) (Serious but less common)
  • Skin necrosis (Rare)
  • Purple toe syndrome (Rare)

Drug-Drug Interactions

  • Antiplatelet agents, NSAIDs, other anticoagulants, certain antifungals, antidepressants, antibiotics that inhibit CYP2C9

Drug-Food Interactions

  • Foods high in vitamin K (e.g., green leafy vegetables) can decrease efficacy

Drug-Herb Interactions

  • St. John’s Wort, ginkgo biloba, garlic, ginseng (may increase bleeding risk)

Nursing Implications

Assessment: Assess for bleeding, monitor INR regularly, assess dietary vitamin K intake.

Diagnoses:

  • Risk for bleeding

Implementation: Administer with consistent vitamin K intake, adjust dose based on INR, educate patient on bleeding precautions.

Evaluation: Maintain INR within therapeutic range (typically 2.0–3.0) for the indication.

Patient/Family Teaching

  • Report unusual bleeding or bruising immediately.
  • Maintain consistent intake of vitamin K-rich foods.
  • Avoid alcohol and herbal supplements without consulting healthcare provider.
  • Use soft toothbrush and electric razor to minimize bleeding risk.

Special Considerations

Black Box Warnings:

  • Significant and sometimes fatal bleeding risk.
  • Pregnancy category X: contraindicated during pregnancy—especially during the first trimester—due to risk of fetal bleeding and teratogenicity.

Genetic Factors: CYP2C9 and VKORC1 genetic variations affect dosing.

Lab Test Interference: Warfarin affects INR, which is used to monitor therapy.

Overdose Management

Signs/Symptoms: Excessive bleeding, hematuria, hematomas, hemoptysis.

Treatment: Discontinue warfarin; administer vitamin K (phytonadione); in severe cases, consider fresh frozen plasma or prothrombin complex concentrates.

Storage and Handling

Storage: Store at room temperature, protected from light and moisture.

Stability: Stable under recommended conditions, check 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.