Pharmacology Case Study Scenarios

Scenario 1: Mark Johnson (72 years old, DVT Treatment with Warfarin)

Problem

Mark is on warfarin (5 mg daily) for Deep Vein Thrombosis (DVT) and has a history of hypertension, hyperlipidemia, and osteoarthritis. He is also taking HCTZ (25 mg daily), celecoxib (200 mg daily), fluvastatin (40 mg daily), and Goody's Powder (as needed for pain). There are potential drug-drug interactions between warfarin, celecoxib, and Goody's Powder (which contains aspirin). Additionally, Mark's warfarin dose might need adjustments due to his risk of bleeding, influenced by his concurrent medications and potential CYP2C9 polymorphism (Holail et al., 2022).

Medication Adjustments

1. Warfarin: Continue warfarin but closely monitor INR levels (target INR for DVT: 2-3) (McRae et al., 2021).

Prescription: Warfarin 5 mg po daily, #30 (30-day supply), 0 refills. Monitor INR in 3-5 days.

2. Celecoxib: Discontinue celecoxib due to its interaction with warfarin, which increases the risk of bleeding.

Alternative: Acetaminophen 500 mg po q6h prn for pain.

Prescription: Acetaminophen 500 mg, #60 (15-day supply), no refills. Max 4g/day.

3. Goody's Powder: Discontinue due to aspirin's interaction with warfarin, increasing the risk of bleeding.

Alternative: As above, acetaminophen for pain relief.

4. HCTZ and Fluvastatin: Continue both, as they do not have significant interactions with warfarin.

Impact of CYP2C9 Polymorphism

A CYP2C9 polymorphism can reduce warfarin metabolism, increasing its effect and raising the risk of bleeding. In such cases, a lower starting dose of warfarin is recommended, and more frequent INR monitoring would be essential. Genetic testing for CYP2C9 variants may be considered to guide therapy (Duarte & Cavallari, 2021).

Monitoring

INR levels should be checked every 3-5 days until stabilized within the therapeutic range (2-3). Liver function and signs of bleeding (e.g., bruising, dark stools) should be monitored.

References

Duarte, J. D., & Cavallari, L. H. (2021). Pharmacogenetics to guide cardiovascular drug

therapy.Nature Reviews Cardiology,18(9), 649-665.

Holail, J., Mobarak, R., Al-Ghamdi,...

(2022). Association of

VKORC1 and CYP2C9 single-nucleotide polymorphisms with warfarin dose adjustment in Saudi patients.Drug metabolism and personalized therapy,37(4), 353-359.

McRae, H. L., Militello, L., & Refaai, M. A. (2021). Updates in anticoagulation therapy

monitoring.Biomedicines,9(3), 262.

Scenario 2: Pill Identifier (P 80)

Medication Identification

The pill with imprint P 80, round, yellow, and scored is Atorvastatin 80 mg, used for lowering cholesterol levels (Surma et al., 2023).

First-Pass Effect

The first-pass effect refers to the metabolism of a drug by the liver after oral administration, which reduces the amount of active drug reaching systemic circulation. For atorvastatin, the first-pass effect is...

…K., Abdulrahim, J., Shah, N., Pagidipati, N. P., ... & Jones,

W. S. (2020). Risk factor burden and long?term prognosis of patients with premature coronary artery disease.Journal of the American heart association,9(24), e017712.

Scenario 4: Sandra (55-year-old African American Female, Hypertension)

Problem

Sandra was prescribed Toprol XL (metoprolol succinate) 50 mg daily for hypertension but is non-adherent due to side effects. Her current blood pressure is 158/92 mmHg, above the target of <140/90 mmHg for African Americans, according to the JNC 8 guidelines.

Medication Therapy

1. Switch to Amlodipine 5 mg po daily.

A calcium channel blocker is preferred in African American patients as first-line therapy for hypertension.

Prescription: Amlodipine 5 mg, #30 (30-day supply), 1 refill.

2. Venlafaxine: Continue for depression as prescribed (225 mg daily).

Patient Education

Discuss the importance of medication adherence to prevent complications such as stroke or heart attack (Pina et al., 2021). Educate about the benefits and potential side effects of the new medication (amlodipine) compared to metoprolol (Lee et al., 2023).

Goal Blood Pressure

Target BP: <140/90 mmHg for African Americans per JNC 8 guidelines.

Monitoring

BP should be rechecked in 4 weeks after initiating therapy. Monitor for signs of peripheral edema, a side effect of amlodipine (Sadaka et al., 2022).

References

Lee, E. M. (2023). Calcium…