Treatment for atrial fibrillation.
SCENARIO 1
A 52-year-old man was recently discharged from the hospital following treatment for atrial fibrillation. He was discharged on Warfarin 5 mg po q day and Amiodarone 200 mg tid. His INR is 8.8. What interaction has occurred with these 2 medications? What changes in his medications would you make?
SCENARIO 2
A 44-year-old women is currently taking Glipizide and Phenytoin. She has a new prescription for Ceftriaxone. All three medications are known to be highly protein bound. What effect does protein binding have on drug availability? How would you manage this patient’s medication?
SCENARIO 3
Name two drugs that are highly affected by the first pass effect. As a prescriber, what actions would you take in prescribing these drugs to counter the first pass effect?
SCENARIO 4
James is a 49-year-old male that was prescribed atenolol for his high blood pressure. James states that he only occasionally takes the medication because he does not like the side effects. What information would you provide to the patient at his visit? How would you manage his medication? What alternative might you prescribe (include a complete medication order)?
Sample Solution
Scenario Responses:
Scenario 1: Warfarin and Amiodarone Interaction
Interaction: Warfarin is a blood thinner and its effect is dependent on achieving a specific INR (International Normalized Ratio) level. Amiodarone can increase the effect of Warfarin, leading to a dangerously high INR (8.8 in this case) and an increased risk of bleeding.
Medication Changes:
- Hold Amiodarone: This is the most likely initial step. The doctor will need to assess the reason for amiodarone use and consider alternative medications or monitor the patient closely if Amiodarone is essential.
- Warfarin Dose Adjustment: The doctor will likely significantly decrease the Warfarin dose or temporarily hold it until the INR reaches a safer range (typically 2-3).
- INR Monitoring: Frequent INR monitoring will be necessary to ensure the new Warfarin dose achieves the target INR.
- Monitor for Displacement: The doctor will be aware of this potential interaction and monitor the patient for signs of Glipizide or Phenytoin toxicity.
- Dose Adjustment: If signs of toxicity occur, the doctor might adjust the dose of Glipizide or Phenytoin.
- Alternative Antibiotic: In some cases, the doctor might choose a different antibiotic that is less protein-bound.
- Buspirone (anti-anxiety): Significant first-pass metabolism reduces its bioavailability.
- Propranolol (beta-blocker): A large portion is metabolized during the first pass, so a higher oral dose is needed compared to other routes.
- Higher Oral Doses: Prescribe a higher dose of the medication to account for the first-pass effect.
- Alternative Route: Consider alternative routes with less first-pass metabolism, such as sublingual, intravenous, or inhaled administration (if available).
- Monitor Blood Levels: Monitor blood levels of the medication to ensure therapeutic effects are achieved.
- Explain the importance of taking Atenolol regularly to control high blood pressure and prevent complications like heart attack or stroke.
- Discuss side effects and explore alternative management strategies (e.g., lifestyle changes) to potentially reduce medication side effects.
- Offer resources or support groups to help with medication adherence.
- Review alternative Atenolol formulations: Discuss if a different formulation (long-acting, beta-blocker combination) might be better tolerated.
- Consider alternative medications: Explore other blood pressure medications with different side effect profiles if Atenolol is not tolerated.
- Lisinopril 10mg daily (once a day dosing can improve adherence)