Case study: Part I GA, an 82-year-old female, presents to her primary care provider for a follow-up visit. GA was hospitalized three months earlier after sustaining a hip fracture from a supervised fall in the assisted living facility where she has resided for the past two years. The patient’s current medical problems include hypertension, osteoporosis, hyperlipidemia, diabetes mellitus type 2, overactive bladder with intermittent incontinence, osteoarthritis, anemia, sleep dysregulation, and residual lower extremity pain from her hip fracture. Caregivers and family members have recently observed forgetfulness and repetitive questioning by the patient. A medication history conducted on the day of the current office visit resulted in the following medication list: ● Lisinopril 5 mg every morning. ● Calcium carbonate 600 mg with vitamin D every morning.
● Simvastatin 10 mg every evening. ● Glipizide sustained release 10 mg every evening with dinner. ● Naproxen 500 mg twice daily. ● Ferrous sulfate 325 mg twice daily. ● Pantoprazole 40 mg every morning (initiated as stress ulcer prophylaxis during her hospital stay three months ago). ● Oxybutynin XL 15 mg every morning. ● Tramadol 50 mg every 6 hours if needed for pain. ● Zolpidem 5 mg at bedtime if needed for sleep. As a member of GA’s patient care team, you must contribute to the safe and effective selection, use, or avoidance of medications to achieve desired clinical outcomes for the conditions that require treatment while minimizing adverse effects. As you review the material below, consider what changes to the medication regimen should be made. This case will be revisited at the end.
THE PHARMACOLOGIC BASIS FOR PRESCRIBING MEDICATIONS
A core principle in Western medicine is that the use of medications should be based on the understanding that the pharmacologic properties of that medication will address the underlying clinical finding or symptom. Most clinical findings are associated with an underlying pathology, a characteristic or process that can be objectively identified and not present in patients void of the same clinical finding. Functional conditions occur when a patient reports symptoms for which an underlying pathology cannot be identified. In principle, a prescriber managing a patient with a functional or pathologic condition for which treatment is intended should make treatment decisions using a sound pharmacologic basis. Pharmacology is the study of how a drug affects the body and encompasses several core factors: Pharmacokinetics and pharmacodynamics (Figure 1). Understanding how a drug works (whether its mechanism of action involves a receptor or other physiologic response) is largely generalizable regardless of age, gender, or other patient factors. Also, the details of how a drug becomes available in and is removed from the body (pharmacokinetics [PK]) and what response a drug elicits once it reaches the site of action (pharmacodynamics [PD]) are well- established principles. However, significant individual variations due to age, development, organ function, genetics, concomitant conditions, and other factors may lead patients to experience a different response to the same medication (Figure 2). A firm understanding of the principal elements of pharmacology is critical to safe and clinically sound prescribing practices. Knowledge deficits and/or failures to account for patient-specific factors may lead to suboptimal or unsafe outcomes.
Figure 1: Adverse Effect +/- Toxicity
Figure 2. Pharmacogenomics and Other Influences on Drug Response
Note. Adapted from Vesell & Penno, 1983.
Mechanism of action Before prescribing a medication, a prescriber must understand not only what the medication is effective in treating (indication) but also how it elicits its clinical effect. A drug’s mechanism of action forms the basis for selecting one therapeutic option
over another. Consider the variety of medication classes that are effective in treating hypertension. While angiotensin- converting enzyme inhibitors (ACEIs), beta-blockers, diuretics, calcium channel blockers, vasodilators, and other medications
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