Case studies: May 2022

Case 1: A local provider calls the pharmacy to ask about SJ, a 67-year-old patient. SJ recently underwent pharmacogenetic testing and was found
have a CYP2C19 mutation; she is an ultra-metabolizer of this enzyme. The provider wants the pharmacist to help assess SJ’s medications and provide any necessary recommendations. The pharmacist reviews SJ’s profile and notes the following medications: atorvastatin 80mg once daily, clopidogrel 75mg once daily, losartan 100mg once daily, omeprazole 20mg once daily, paroxetine 10mg once daily daily and voriconazole 200 mg twice daily.

What should the pharmacist recommend?

A: Pharmacogenetic testing is becoming popular and can provide information about specific differences in the expression of an enzyme that may affect drug metabolism. Knowing this information can help clinicians select and/or modify drug therapy. Ultra-rapid metabolizers metabolize drugs at much faster rates than normal, so the lack of therapeutic effect is a concern. After reviewing SJ’s medications, an increase in the dose of omeprazole is needed to achieve therapeutic levels in this patient. However, omeprazole may also interact with clopidogrel, decreasing its antiplatelet effect. Instead, the pharmacist may recommend switching to pantoprazole 40 mg daily. Additionally, based on the enzyme mutation, voriconazole is unlikely to reach therapeutic levels, so an alternative such as posaconazole should be considered. No other medication would require adjustment, but SJ should still be monitored for an adequate clinical response.

Reference

1. Guidelines. Clinical Pharmacogenetics Implementation Consortium. Updated March 26, 2021. Accessed April 14, 2022. https://cpicpgx.org/guidelines/

Case 2: AR, a 32-year-old woman who takes her monthly birth control pill, mentions that she has recently been feeling more anxious and
his heart won’t stop beating. She has been under more stress than normal at work and believes this is the cause of her symptoms. AR says the frequency and severity of his migraines have also increased over the past month, prompting his primary care provider (PCP) to add propranolol 20mg twice daily for prophylaxis. His current medications are drospirenone 3mg/ethinylestradiol 0.02mg daily, propranolol 20mg twice daily; sumatriptan 100 mg as a single dose at the onset of migraine, and 0.3% adapalene/2.5% benzoyl peroxide gel, applied to affected skin once daily.

Aside from stress, what medication-related problem could account for AR complaints?

A: RA may show early signs of hyperkalemia, the symptoms of which include abdominal pain, arrhythmia or heart palpitations, chest pain, diarrhea, muscle weakness, and nausea.1 AR’s oral contraceptive contains drospirenone. Drospirenone is a spironolactone analogue with antimineralocorticoid activity that can spare potassium. In addition, non-selective β-blockers such as propranolol decrease the cellular uptake of potassium.2 Although the individual risk of hyperkalemia with both drugs is low, combined use may have an additive effect. To confirm, the pharmacist may recommend that AR follow up with his PCP as soon as possible to obtain a potassium sample. If her potassium is high, other pharmacological migraine prophylaxis should be discussed.

References

1. Cleveland Clinic. Updated October 5, 2020. Accessed March 24, 2022. https://my.clevelandclinic.org/health/diseases/15184-hyperkalemia-high-blood-potassium

2. Mandić D, Nezić L, Skrbić R. Severe propranolol-induced hyperkalemia. Preset med. 2014;67(5-6):181-184.

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