Case Study For Pharmacodynamics and Pharmacokinetics in Older Patients

Introduction

The geriatric populations are at an increased risk for developing multiple comorbidities, including hypertension, diabetes mellitus, and cardiovascular diseases. Consequently, the treatment of this disease requires multiple medications. The mechanism and metabolism of the medications administered may shift among this patient as aging results in changes in physiology which impact the drug’s pharmacokinetics and pharmacodynamics processes. In patients’ cardiovascular diseases and other comorbidities, drug-to-drug interactions are a factor that may also affect the pharmacokinetic and pharmacodynamics process. This paper discusses how age as a factor in patient BN in the case study influences the pharmacodynamics and pharmacokinetic process, how the change influences the drug therapy, and how to improve the patient’s drug therapy. Case Study For Pharmacodynamics and Pharmacokinetics in Older Patients

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Factors affecting pharmacodynamics and pharmacokinetic process in the patient

Age is a factor that will influence the pharmacodynamics and pharmacokinetic process of patient BN. Pharmacokinetics is a drug’s movement in the body, including absorption, distribution, metabolism, and excretion. In elderly patients, significant changes may occur, some of which are more clinically relevant. Aging causes a considerable decrease in the metabolism and excretion of many drugs. A reduction in metabolism and excretion rate may cause toxicity because the concentrations of chronically used medications increase by 5 to 6 half-lives. According to Thürmann (2020), age reduces the small-bowel surface area, slows gastrointestinal motility, and increases gastric Ph. This may result in delayed absorption and onset of action. For example, the onset of action for Lisinopril may be affected because of the decreased absorption and bioavailability. Aging also causes an increase in body fat and reduces total body water. This is associated with increased volume distribution and increased elimination of half-lives for some drugs, such as metoprolol.

Pharmacodynamics is the study of the drug’s interaction with the body. In geriatric patients, the efficacy of the same drug concentrations on different action sites may vary compared to those in younger populations. The changes observed are attributed to drug-receptor interactions, adoptive homeostatic responses, post-receptor events, and pathologic changes in different organs (Thürmann, 2020)Case Study For Pharmacodynamics and Pharmacokinetics in Older Patients. There is also increased sensitivity to anticholinergic drug effects. Medications such as antidepressants, antihyperglycemics, antidepressants, antihypertensive, and urinary antimuscarinic agents have an anticholinergic effect, and as such, patients using such drugs must be monitored frequently.

Impact of the change in processes of the recommended drug therapy

As Thürmann (2020) discusses, aging is associated with increased gastric Ph, reduced stomach surface area, and reduced excretion of drugs. These changes impact the pharmacokinetic and pharmacodynamics processes of the recommended drug therapy for patient BN. For example, in the case of Lisinopril, the drug’s absorption level may increase in the small intestines but may reduce its bioavailability. Aging also decreases the overall hepatic metabolism for specific medications, decreasing the clearance rate to approximately 30 to 40%. As a result, there is an increased risk for higher toxic effects. For example, the hepatic metabolism of diltiazem may be reduced, which may increase the risk of toxicity

Aging is also associated with reduced renal elimination of some medications. The decrease in renal elimination has clinically significant implications for patient toxicity levels. For example, the renal elimination of digoxin and Lisinopril will reduce significantly. There is also an increased fat and decreased total water mass in old patients (Andres et al., 2019)Case Study For Pharmacodynamics and Pharmacokinetics in Older Patients. This may affect the diffusion of certain medications. In the case of patient BN, the distribution and uptake of the metoprolol and digoxin may reduce, which may result in significant clinical implications. Aging is associated with changes in sensitivity to different drug concentrations, which may affect the pharmacodynamics process. For example, in inpatient BN, the response to diltiazem may differ from that of a younger patient.

Improving the patient’s drug therapy plan

Different approaches may help optimize the drug therapy plan for patient BN. Providers must choose the best drugs and correct dosage for older patients while monitoring for effectiveness and toxicity and patient education about adverse health outcomes (Sleder et al., 2015)Case Study For Pharmacodynamics and Pharmacokinetics in Older Patients. For patient BN, some adjustments may be made. For instance, the diltiazem dosage may be decreased because of its decrease in mechanism and increased volume in distribution. The efficacy of the dose must be monitored, and if the slightest efficacy, then the drug dosage should not be increased. Digoxin must also be used cautiously because of its reduced renal elimination, which may increase toxicity. In addition, its clearance level also increases. Therefore, the dosage should be adjusted to start with at least 0.125mg and adjusted according to the response (Sleder et al., 2015). Metoprolol and Lisinopril also have reduced renal elimination and thus should be administered at lower dosages, and the dose increased until the lowest efficacy is achieved. In addition, educating the patients about the possible side effects of the medications is essential. With the drug therapy plan adjustment, optimal health outcomes for patient BN will be achieved.

Conclusion

In summary, age is a factor that affects pharmacodynamics and pharmacokinetic processes. Older patients experience pathologic changes in body organs, which affect the drug’s mechanism and metabolism. This is affected by certain factors, including increased gastric Ph, reduced bowel surface area, increased body fat, reduced total body water, reduced renal elimination, and reduced metabolism. Therefore, medications among the elderly must be first administered at lower dosages while monitoring the efficacy, toxicity, and side effects.

References

Andres, T. M., McGrane, T., McEvoy, M. D., & Allen, B. F. S. (2019). Geriatric pharmacology. Anesthesiology Clinics, 37(3), 475–492. https://doi.org/10.1016/j.anclin.2019.04.007

Sleder, A. T., Kalus, J., & Lanfear, D. E. (2015). Cardiovascular Pharmacokinetics, pharmacodynamics, and pharmacogenomics for the clinical practitioner. Journal of Cardiovascular Pharmacology and Therapeutics, 21(1), 20–26. https://doi.org/10.1177/1074248415590196

Thürmann, P. A. (2020). Pharmacodynamics and pharmacokinetics in older adults. Current Opinion in Anaesthesiology, 33(1), 109–113. https://doi.org/10.1097/aco.0000000000000814 Case Study For Pharmacodynamics and Pharmacokinetics in Older Patients

BY DAY 7 OF WEEK 2

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.

Case Study 

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. Case Study For Pharmacodynamics and Pharmacokinetics in Older Patients

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
  

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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 Case Study For Pharmacodynamics and Pharmacokinetics in Older Patients

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 102

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