A 44-year-old women is currently taking Glipizide and Phenytoin

In Week 2, we will continue our pharmacology journey and apply the concepts to the cardiovascular system. Pharmacodynamics and pharmacokinetics are the two branches of pharmacology. Remember, pharmacokinetics describes what the body does to the drug through absorption, distribution, metabolism, and excretion (ADME), whereas pharmacodynamics describes what the drug does to the body.
When selecting drugs and determining dosages for patients, it is essential to consider individual patient factors that might impact the patient’s pharmacokinetic and pharmacodynamic processes. These patient factors include genetics, gender, ethnicity, age, behavior (ie diet, nutrition, smoking, alcohol, illicit drug abuse), and/or pathophysiological changes due to disease.

Assignment instruction
Review the case studies (attachment) and answer ALL questions. Use article that’s less than 5years.
• When recommending medications, write out a complete prescription for each medication. What order would you send to a pharmacy? Include drug, dose, route, frequency, special instructions, # dispensed (days supply), refills, etc. Also state if you would continue, discontinue or taper the patient’s current medications.
• Use clinical practice guidelines in developing your answers. Please review all Required Learning Resources. Use the Medscape app or website and EHS guidelines to complete the assignment.
• Include at least three references to support each scenario and cite them in APA format. Please include in-text citations.
• You do not need an introduction orconclusion paragraph.

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)?

_______________

SCENARIO 1:
Warfarin and amiodarone have a significant drug interaction that can lead to an elevated INR and increased bleeding risk. Amiodarone inhibits the metabolism of warfarin by the CYP2C9 enzyme, leading to higher warfarin levels (Trailokya et al., 2018). With an INR of 8.8, this patient is at high risk for bleeding.

Medication changes:
– Discontinue warfarin and amiodarone
– Administer vitamin K 10 mg IV x 1 dose to reverse warfarin’s effects
– Once INR is therapeutic, consider restarting warfarin at a lower dose (2.5 mg po daily) and monitor INR closely
– Consider alternative antiarrhythmic such as sotalol or dronedarone that has less interaction with warfarin

SCENARIO 2:
Highly protein-bound drugs like glipizide, phenytoin, and ceftriaxone can compete for binding sites on albumin. This competition can displace other bound drugs, increasing their free unbound concentrations and pharmacological effects (Sato et al., 2019). Phenytoin has a narrow therapeutic index, so small changes in unbound concentration can lead to toxicity.

Management:
– Monitor patient closely for signs of phenytoin toxicity (ataxia, nystagmus, confusion)
– Check phenytoin free and total levels
– Consider alternative antibiotic with less protein binding, such as levofloxacin
– If continuing ceftriaxone, may need to decrease phenytoin dose and recheck levels in 5-7 days

SCENARIO 3:
Two drugs highly affected by first-pass metabolism are:
1. Nitroglycerin – extensive first-pass effect in the liver, so it is administered sublingually or transdermally to avoid this (Katzung, 2021)
2. Lidocaine – high first-pass effect, so it is often given IV, topically or by nebulizer to avoid oral administration (Shahid et al., 2020)

To counter first-pass metabolism:
– Use alternate routes like sublingual, IV, topical, transdermal to bypass the liver
– Give prodrug that is activated after first-pass (e.g. enalapril)
– Use drug not extensively metabolized by the liver

SCENARIO 4:
Counsel James on the importance of taking atenolol regularly as prescribed for managing hypertension. Explain that abruptly stopping atenolol can cause rebound hypertension. If side effects are bothersome, he should discuss with his provider rather than self-discontinuing.

Management:
– Check blood pressure and heart rate
– Encourage lifestyle modifications – low sodium diet, exercise, weight loss
– If blood pressure not at goal, increase atenolol dose
– If bradycardia or other intolerable side effects, consider alternative medication

Alternative prescription:
Lisinopril 10 mg po daily #30, Refills: 5
Take one tablet by mouth daily for high blood pressure

References:
Katzung, B. G. (2021). Basic & Clinical Pharmacology, 15th edition. McGraw-Hill Education.

Sato, T., Yamaguchi, H., Kogawa, T., Abe, T., & Mano, N. (2019). Potential Drug Interactions Mediated by Serum Protein Binding. American Journal of Medical Sciences and Medicine, 7(1), 1-7.

Shahid, A., Majeed, M., & Khokhar, M. A. (2020). Lidocaine. StatPearls Publishing.

Trailokya, A., Hiremath, J. S., & Sawhney, J. (2018). Amiodarone-Warfarin Drug Interaction: Reaffirmed. Journal of the Association of Physicians of India, 66(12), 79-80.