Question

question 68

a pharmacy technician receives a prescription for warfarin (coumadin). the technician should recognize that which of the following is a critical drug interaction concern for patients taking warfarin?

warfarin is incompatible with all antibiotics.
nsaids such as ibuprofen can increase the risk of bleeding when taken with warfarin.
warfarin should never be taken with food.
taking warfarin with antacids decreases its effectiveness.

Explanation:

Analyze the clinical pharmacology of warfarin

Warfarin (Coumadin) is an oral anticoagulant that inhibits the synthesis of vitamin K-dependent clotting factors. Because it prevents blood clots, its most significant and dangerous side effect is bleeding. Any concurrent medication that also affects clotting mechanisms or damages the gastrointestinal mucosa will compound this risk, leading to potentially life-threatening Adverse Drug Reactions.

Evaluate the drug interaction with NSAIDs

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen, and aspirin, inhibit cyclooxygenase (COX) enzymes. This action reduces platelet aggregation (which impairs primary hemostasis) and decreases protective prostaglandins in the stomach lining, increasing the risk of gastrointestinal mucosal bleeding. When a patient takes an NSAID concurrently with warfarin, these two distinct mechanisms combine to dramatically elevate the risk of serious bleeding.

Assess the remaining options

• Warfarin is incompatible with all antibiotics: While many antibiotics interact with warfarin (often by altering gut flora that synthesize vitamin K or inhibiting warfarin metabolism), it is not incompatible with all of them. Some can be used with close monitoring of the International Normalized Ratio (INR).
• Warfarin should never be taken with food: Warfarin can be taken with or without food. However, patients must maintain a consistent intake of vitamin K-rich foods (like leafy greens) to avoid fluctuating INR levels.
• Taking warfarin with antacids decreases its effectiveness: Antacids do not have a clinically significant impact on the absorption or overall therapeutic effectiveness of warfarin.

Answer:

• (A) Warfarin is incompatible with all antibiotics.
• (B) NSAIDs such as ibuprofen can increase the risk of bleeding when taken with warfarin. (Correct answer)
• (C) Warfarin should never be taken with food.
• (D) Taking warfarin with antacids decreases its effectiveness.