Discussion: Pharmacokinetics And Pharmacodynamics

As an advanced practice nurse assisting physicians in the diagnosis and treatment of disorders, it is important to not only understand the impact of disorders on the body, but also the impact of drug treatments on the body. The relationships between drugs and the body can be described by pharmacokinetics and pharmacodynamics.

Pharmacokinetics describes what the body does to the drug through absorption, distribution, metabolism, and excretion, whereas pharmacodynamics describes what the drug does to the body.

When selecting drugs and determining dosages for patients, it is essential to consider individual patient factors that might impact the patient’s pharmacokinetic and pharmacodynamic processes. These patient factors include genetics, gender, ethnicity, age, behavior (i.e., diet, nutrition, smoking, alcohol, illicit drug abuse), and/or pathophysiological changes due to disease.

For this Discussion, you reflect on a case from your past clinical experiences and consider how a patient’s pharmacokinetic and pharmacodynamic processes may alter his or her response to a drug.

To Prepare
  • Review the Resources for this module and consider the principles of pharmacokinetics and pharmacodynamics.
  • Reflect on your experiences, observations, and/or clinical practices from the last 5 years and think about how pharmacokinetic and pharmacodynamic factors altered his or her anticipated response to a drug.
  • Consider factors that might have influenced the patient’s pharmacokinetic and pharmacodynamic processes, such as genetics (including pharmacogenetics), gender, ethnicity, age, behavior, and/or possible pathophysiological changes due to disease.
  • Think about a personalized plan of care based on these influencing factors and patient history in your case study.
By Day 3 of Week 1

Post a description of the patient case from your experiences, observations, and/or clinical practice from the last 5 years. Then, describe factors that might have influenced pharmacokinetic and pharmacodynamic processes of the patient you identified. Finally, explain details of the personalized plan of care that you would develop based on influencing factors and patient history in your case. Be specific and provide examples.

By Day 6 of Week 1

Read a selection of your colleagues’ responses and respond to at least two of your colleagues on two different days by suggesting additional patient factors that might have interfered with the pharmacokinetic and pharmacodynamic processes of the patients they described. In addition, suggest how the personalized plan of care might change if the age of the patient were different and/or if the patient had a comorbid condition, such as renal failure, heart failure, or liver failure.

Note: For this Discussion, you are required to complete your initial post before you will be able to view and respond to your colleagues’ postings. Begin by clicking on the “Post to Discussion Question” link, and then select “Create Thread” to complete your initial post. Remember, once you click on Submit, you cannot delete or edit your own posts, and you cannot post anonymously. Please check your post carefully before clicking on Submit!

Discussion 1 NG

Introduction

This post is an attempt to discuss risk factors associated with prescribing medications to the elderly population. It is also an attempt to understand the challenges clinicians encounter with age-related concerns with pharmacokinetic and pharmacodynamic processes. Additionally, it will also explain that a personalized plan of care necessitates medication adherence.

Chief Complaint

A 72-year-old male patient with CC of worsening psychosis and not cooperative with assessment. Patient has history of CHF, alcohol abuse, and smoking about a pack of cigarettes a day. On physical assessment, SBP 164/78 HR 99 RR 19 PaO2 96%. Per ED report, patient was found lying on the floor with half bottle of vodka next to him. Patient’s neighbor called 911. Per EMS, patient has not been compliant with taking his medications. Last hospital encounter was for alcohol intoxication.

Risk Factors

Possible risk factors that influence pharmacokinetic and pharmacodynamic processes include patient’s age, sex, severe alcohol use, comorbidities related to heart, renal and hepatic function with age-related changes. When prescribing medication, clinicians should be aware of the adverse effects related to hepatic and renal function of the elderly. An example is with SSRIs, these medications are hepatically metabolized and highly protein bound. Despite these properties, the pharmacokinetics of SSRIs may differ in elderly patients due to decreased drug clearance as a result from the natural decline in renal function with age, even with the absence of renal disease (Cossart, Isbel, Scuderi, Campbell, & Staatz (2021). Another risk factor that may also play a major role is the individual response to a given pharmacologic agent is the genetic makeup of the patient (Kassimis, & Alexopoulos, 2018). Essentially, genetic makeup of the patient refers to the role of genetic variation in response to a drug (Kassimis et al., 2018). These risk factors play a crucial role with a drug’s absorption, distribution, metabolism, and elimination, all of which affect the drug’s effect by altering the drug’s concentration at its site of action (Cossart et al., 2021). An increased volume of distribution may result from the proportional increase in body fat relative to skeletal muscle with aging (Alhawassi, Alatawi & Alwhaibi. 2019). Larger drug storage reservoirs and decreased clearance prolong drug half-lives and lead to increased plasma drug concentrations in older people (Alhawassi, 2019). Lastly, pharmacodynamics refers to the patient’s body’s therapeutic response to a drug (Cossart et al., 2021). This generally is determined by the drug’s affinity and activity at its site of action, which is often a receptor (Cossart et al., 2021).

Personalized Plan of Care

The process of prescribing a medication is complex because of the difficult challenges that a clinician face when prescribing a medicine for older adults. These challenges may include deciding that a drug is indicated, choosing the best drug, determining a dose, and scheduling an appropriate time pending on the patient’s physiologic status. These complexities may also present unique challenges when prescribing for an elderly patient due to care with monitoring for effectiveness and toxicity, educating the patient about expected side effects, and encouraging the patient to look for indications that may render medical consultation (Cossart et al., 2021). The care in prescribing medicine become even more cumbersome when premarketing drug trials often exclude geriatric patients because they may not be appropriate for older adults (Cossart et al., 2021). As such, many medications need to be used with special caution because of age-related changes in pharmacokinetics and pharmacodynamics (Kuchel, 2018). An example is the  clearance rate for lithium is reduced, in older adults (Nagamine, 2020). The same dose of medication would lead to higher plasma concentrations in an older, compared with younger, patient (Nagamine, 2020.) Hepatic function also declines with advancing age, and age-related changes in hepatic function may account for significant variability in drug metabolism among older adults. Especially when polypharmacy is a factor, decreasing hepatic function may lead to adverse drug reactions (Alhawassi, 2019). During the assessment, we can determine that patient has a history with not taking his medications. Use of multiple medications can lead to problems with adherence in older adults, especially, compounded by a complex drug regimen (Sutema, Jaya & Bakta, 2018). The clinician recognizes that patient preference and treatment availability may be overriding factors in selecting a treatment modality. For patients who lack motivation for treatment, motivational interviewing can be a useful initial intervention (Weng, Ding, Min, Tang, Yang, Guo & Xing, 2019).  This may include a brief motivational alcohol counseling as a starting point for patients with an alcohol use disorder (Weng et al., 2019). In selecting psychosocial interventions, the clinician should make the patient aware of the menu of options and his best clinical advice and allow the patient to choose among them (Weng et al., 2019).

Conclusion

The issue of polypharmacy is of particular concern in older people who tend to have more disease conditions for which medications are prescribed. The use of greater numbers of drug therapies has been independently associated with an increased risk for an adverse drug event with respect to age-related challenges in the elderly. As such, the clinician should take caution in prescribing medications for the elderly population.

References

Amelia R. Cossart, Nicole M. Isbel, Carla Scuderi, Scott B. Campbell, & Christine E. Staatz. (2021). Pharmacokinetic and Pharmacodynamic Considerations in Relation to Calcineurin Usage in Elderly Kidney Transplant Recipients. Frontiers in Pharmacology12. https://doi-org.ezp.waldenulibrary.org/10.3389/fphar.2021.635165

Ida Ayu Manik Partha Sutema, Made Krisna Adi Jaya, & I Made Bakta. (2018). Medicine reminder to improve treatment compliance on geriatric patients with diabetic neuropathy at Sanglah Central Hospital, Bali-Indonesia. Bali Medical Journal7(2), 516–520. https://doi-org.ezp.waldenulibrary.org/10.15562/bmj.v7i2.1070

Kassimis, G., & Alexopoulos, D. (2018). CYP2C19 Genetic Polymorphism and Pharmacodynamics of Prasugrel Maintenance Dose in Patients Undergoing Percutaneous Coronary Intervention. Cardiology140(4), 237–238.

Kuchel, G. A. (2018). Frailty and Resilience as Outcome Measures in Clinical Trials and Geriatric Care: Are We Getting Any Closer? Journal of the American Geriatrics Society66(8), 1451–1454. https://doi-org.ezp.waldenulibrary.org/10.1111/jgs.15441

Nagamine, T. (2020). Lithium intoxication in the elderly: A possible interaction between azilsartan, fluvoxamine, and lithium. Innovations in Clinical Neuroscience, 17(4–6), 45–46.

Tariq M. Alhawassi, Wafa Alatawi, & Monira Alwhaibi. (2019). Prevalence of potentially inappropriate medications use among older adults and risk factors using the 2015 American Geriatrics Society Beers criteria. BMC Geriatrics, 19(1), 1–8. https://doi-org.ezp.waldenulibrary.org/10.1186/s12877-019-1168-1

Weng, W., Ding, S., Min, J., Tang, H., Yang, H., Guo, P., & Xing, S. (2019). Logistic regression analysis of drug compliance and influencing factors in elderly osteoporosis patients. Pakistan Journal of Pharmaceutical Sciences, 32(5(Special)), 2399–2403.

Discussion 2 SD

NURS 6521 Week 1 Initial Discussion Post

As a hospice nurse, the patients I care for are dealing with advanced stages of disease, some from multiple disease processes.  Most of my patients have issues with metabolism. However, some, such as COPD patients, would have decreased distribution due to their inability to take a deep enough breath to administer an inhaled medication appropriately.

Pharmacokinetics refers to the effects the body has on a drug through the processes of absorption, distribution, metabolism, and excretion.  Pharmacodynamics is the effects of the drug on the body (Rosenthal & Burchum, 2021).  The most interesting patients, as they relate to pharmacokinetics and pharmacodynamics, are liver failure patients.  These patients come to hospice at a late stage of the disease process and are frequently in a lot of pain.  Opioid pain medications are commonly prescribed.  Liver failure patients are at a higher risk of toxicity from opioids due to reduced hepatic function and the effects on metabolic pathways.  Decreased albumin levels in liver failure lead to increased serum drug levels and bioavailability.  Reduction in serum albumin level also changes the quality of opioid distribution.  When opioids accumulate in the plasma, the half-life increases, increasing the severity of adverse reactions such as encephalopathy or respiratory depression (Soleimanpour et al., 2016).  In hospice, the main goal of patient care is symptom relief and comfort.  As a hospice nurse, I have honestly not considered the pharmacokinetics and pharmacodynamics of the medications provided, just the benefit of pain relief for the patient.  In patients who are not in a transitioning or actively dying state, the dosage of opioid medication and dosing intervals should be adjusted according to the severity of the disease process.  Some medications should be avoided entirely, such as meperidine and codeine (Oliverio, Malone, & Rosielle, 2015).

Behavioral factors that may affect a liver failure patient’s pharmacokinetic and pharmacodynamic processes are often a history of alcohol or drug abuse that may be ongoing.  The nutritional status of these patients is often not optimal either due to decreased appetite, pain, and ascites.  Most commonly, liver failure patients are males over age 50, who have abused alcohol, and or have diabetes Type II.  Liver failure patients are at higher risk of developing liver cancer (niddk.nih.gov, 2018).  In a study done by Hernaez et al. (2019), African American males were at higher risk of developing end-stage liver disease.

Pharmacogenetics, or pharmacogenomics, studies how genetics affects a person’s response to drugs.  The goal is to treat each patient individually based on their specific genetic makeup.  For example, some people have many copies of a particular liver enzyme active in metabolizing codeine into morphine.  These people metabolize the drug so wholly and fast that a standard dose for a “normal” patient could be an overdose for them (nigms.nih.gov, n.d.).  Taking pharmacogenetics into consideration, that could further alter the way opioid medications affect a patient with liver failure.

A plan of care for pain management specific to a liver failure patient would consider where the patient is in the disease process.  By the time a patient is referred to hospice, they are generally in advanced stages of the disease.  Active alcohol or illicit drug use is also considered, as pharmacodynamic interactions between alcohol and prescription drugs are common (Fraser, 2012).  Dosage should be decreased, and time intervals increased to lower the risk of adverse reaction while still providing pain relief.  Drug selection is also considered, as meperidine and codeine are contraindicated in liver failure (Oliverio, Malone, & Rosielle, 2015).

References

.

Definition & facts for cirrhosis. (2018, March). NIH National Institute of Diabetes and Digestive and Kidney Diseases. Retrieved June 2, 2021, from https://www.niddk.nih.gov/health-information/liver-disease/cirrhosis/definition-facts

Hernaez, R., Kramer, J. R., Liu, Y., Tansel, A., Natarajan, Y., Hussain, K. B., Ginès, P., Solà, E., Moreau, R., Gerbes, A., El-Serag, H. B., & Kanwal, F. (2019). Prevalence and short-term mortality of acute-on-chronic liver failure: A national cohort study from the USA. Journal of Hepatology70(4), 639–647. https://doi.org/10.1016/j.jhep.2018.12.018

Oliverio, C., Malone, N., & Rosielle, D. (2015, September). Opioid use in liver failure. Palliative Care Network of Wisconsin. Retrieved June 2, 2021, from https://www.mypcnow.org/fast-fact/opioid-use-in-liver-failure/

Pharmacogenomics. (n.d.). NIH National Institute of General Medical Sciences. Retrieved June 2, 2021, from https://www.nigms.nih.gov/education/fact-sheets/Pages/pharmacogenomics.aspx

Rosenthal, L. & Burchum, J. (2021). Lehne’s pharmacotherapeutics for advanced practice nurses and physician assistants (2nd ed.). Saunders.

Soleimanpour, H., Safari, S., Shahsavari Nia, K., Sanaie, S., & Alavian, S. (2016). Opioid drugs in patients with liver disease: A systematic review. Hepatitis Monthly16(4). https://doi.org/10.5812/hepatmon.32636

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