Age as a Factor in Pharmacokinetics and Pharmacodynamics

Heart disease remains the No. 1 killer in America; nearly half of all Americans have high blood pressure, high cholesterol, or smoke—some of the leading risk factors for heart disease…

—Murphy et al., 2018

Despite the high mortality rates associated with cardiovascular disorders, improved treatment options do exist that can help address those risk factors that afflict the majority of the population today.

As an advanced practice nurse, it is your responsibility to recommend appropriate treatment options for patients with cardiovascular disorders. To ensure the safety and effectiveness of drug therapy, advanced practice nurses must consider aspects that might influence pharmacokinetic and pharmacodynamic processes such as medical history, other drugs currently prescribed, and individual patient factors.

Reference: Murphy, S. L., Xu, J., Kochanek, K. D., & Arias, E. (2018). Mortality in the United States, 2017. Retrieved from https://www.cdc.gov/nchs/products/databriefs/db328.htm PHARMACOTHERAPY FOR CARDIOVASCULAR DISORDERS

BN is a 74-year-old African American male who is seeing his PCP because he noticed when he woke up that his “heart was not beating right; it feels like it is going to slow.” He denies chest pain, SOB, N/V. He notes feeling dizzy earlier in the day. 6 weeks earlier his PCP started him on Diltiazem CD to further lower his BP to goal. His Metoprolol was lowered at that time as well from 75 mg to 50 mg BID. His PCP recommends he be admitted to the hospital.

Upon presentation to the hospital:

PMH:

· HTN x 7 years

· Type II DM

· CAD s/p angioplasty 2 years ago

· MI 3 years ago

· EF = 60%

· PVD s/p left femoral to posterior bypass

· Hx of A Fib x 4 years

Medications:

· Digoxin 0.25 mg QD KCl 40 mEq QD Vitamin C 500 mg QD

· Diltiazem CD 180 mg QD ASA EC 325 mg QD Vitamin E 400 IU QD

· Metoprolol 5- mg BID Warfarin 5 mg QD Ibuprofen 200 mg 2 tabs prn headache

· Lisinopril 20 mg QD Famotidine 20 mg QHS Multivitamin QD

· Imdur 30 mg QD Lantus 26u QHS Ca++/Vit D 500mg/200 IU BID

· HCTZ 12.5 mg QD Humalog 8u with meals

PE:

· BP 110/50 Pulse 38 bpm Resp 14/min

· Rest of physical exam unremarkable

Labs:

· K+ 6.9 WBC 5,800/mm3

· Na+ 135 Hct 35%

· Cr 1.9 Dig 2.78

· BUN 35 INR 2.3

· Gluc 10

Write a 2- to 3-page paper that addresses the following:

· Explain how the factor you selected might influence the pharmacokinetic and pharmacodynamic processes in the patient from the case study you were assigned.

· Describe how changes in the processes might impact the patient’s recommended drug therapy. Be specific and provide examples.

· Explain how you might improve the patient’s drug therapy plan and explain why you would make these recommended improvements

To Prepare

· Review the Resources for this module and consider the impact of potential pharmacotherapeutics for cardiovascular disorders introduced in the media piece.

· Review the case study assigned by your Instructor for this Assignment.

· Select one the following factors: genetics, gender, ethnicity, age, or behavior factors.

· Reflect on how the factor you selected might influence the patient’s pharmacokinetic and pharmacodynamic processes.

· Consider how changes in the pharmacokinetic and pharmacodynamic processes might impact the patient’s recommended drug therapy.

· Think about how you might improve the patient’s drug therapy plan based on the pharmacokinetic and pharmacodynamic changes. Reflect on whether you would modify the current drug treatment or provide an alternative treatment option for the patient.

References

https://www.cdc.gov/nchs/products/databriefs/db328.htm

Age as a Factor in Pharmacokinetics and Pharmacodynamics
As the patient is 74 years old, age is an important factor to consider in his pharmacokinetic and pharmacodynamic processes. The kidneys and liver, which are responsible for drug metabolism and excretion, tend to decline in function with age (Gandhi et al., 2019). Specifically, renal blood flow and glomerular filtration rate decrease with age, resulting in reduced clearance of renally eliminated drugs like digoxin, metformin, and diltiazem (Murphy et al., 2016).
Additionally, total body water and fat composition change with age. As people age, total body water decreases while fat composition increases. This alters the volume of distribution for water-soluble and fat-soluble drugs (Gandhi et al., 2019). The patient’s age therefore impacts how his body absorbs, distributes, metabolizes and excretes his current medications.
Impact on Drug Therapy
Reduced renal clearance puts the patient at higher risk for drug accumulation, adverse effects and toxicity from drugs like digoxin and diltiazem that are renally eliminated (Murphy et al., 2016). His elevated potassium level of 6.9 suggests digoxin toxicity has occurred, likely due to reduced clearance in his advanced age. Additionally, the decreased metabolism of drugs by the liver could result in higher than intended drug levels for medications metabolized this way.
Recommended Improvements
Given his age-related changes in pharmacokinetics, several adjustments could be made to his drug therapy plan. First, his digoxin dose should be decreased or the drug discontinued to avoid further toxicity. Second, his diltiazem dose may need to be reduced to avoid excess accumulation over time. Third, more frequent monitoring of renal function, electrolytes, and drug levels is prudent given his increased risk for adverse effects. Finally, an alternative to diltiazem such as a beta-blocker could be considered given concerns about its clearance in his older age. Close monitoring and individualized dosing based on pharmacokinetic changes will be important to safely continue his cardiovascular drug therapy.