Pharmacology & Dosage Calculation

A patient with a history of atrial fibrillation has an order for 0.25 milligrams of drug (X), the available…

A patient with a history of atrial fibrillation has an order for 0.25 milligrams of drug (X), the available supply/dose is 0.125 milligrams. Which of the following doses in correct?

  1. A Dispense two tablets to the patient Correct answer
  2. B Administer one tablet twice daily
  3. C Dispense one half tablet to the patient
  4. D Return tablets to the pharmacy and re-order

Explanation

Core Concept: Accurate drug calculation prevents underdosing or toxicity. Using the standard formula: (Desired Dose / Available Dose) = 0.25 mg / 0.125 mg = 2 tablets. The nurse must administer two 0.125 mg tablets to achieve the ordered 0.25 mg dose. Drug X in this context is likely Digoxin, commonly used for rate control in atrial fibrillation.

Clinical Presentation:

  • Atrial fibrillation presents with an irregular and often rapid heart rate, causing palpitations, shortness of breath, fatigue, and dizziness.
  • Complications include thromboembolism leading to ischemic stroke, and heart failure due to reduced cardiac output.

Diagnosis:

  • First-line diagnostic tool: A 12-lead Electrocardiogram (ECG), which will show an irregularly irregular rhythm, absent P waves, and narrow QRS complexes.
  • Gold standard diagnostic test: A Transesophageal Echocardiogram (TEE) to identify structural heart disease or rule out atrial thrombi (especially in the left atrial appendage) before cardioversion.

Management:

  • Acute management: Rate control (using beta-blockers, calcium channel blockers, or digoxin) and assessing hemodynamic stability (synchronized cardioversion if unstable).
  • Gold standard long-term/definitive management: Stroke prevention with oral anticoagulants (e.g., DOACs like apixaban or warfarin) and long-term rate or rhythm control strategies, potentially including catheter ablation.

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