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Discussion: Pharmacokinetics and Pharmacodynamics

NURS 6521 Discussion: Pharmacokinetics and Pharmacodynamics

Discussion: Pharmacokinetics and Pharmacodynamics

In March 2020 Arkansas began to see the first surge of patients with coronavirus (COVID-19). In the beginning, treatment for the virus was based on oxygen saturation, and symptom management. By August 2021 monoclonal antibodies, Regen-Cov, casirivimab and imdevimab given together became the treatment of choice for the Delta strain of the virus under Emergency Use Authorization by the Food and Drug Administration (FDA.gov).

A 50 y/o male patient with moderate obesity and high blood pressure presented with cough, tachypnea and fever. He reported onset of symptoms eight days prior to seeking treatment and tested positive for COVID-19 using a rapid antigen test. His temperature was 102 degrees, heart rate 124, BP (Blood Pressure) 147/92 and oxygen saturation was 87%. The patient had no known drug allergies. He did not meet inclusion criteria due to his oxygen saturation but after doing some deep breathing, coughing, and sitting upright rather than lying down his oxygen saturation increased to 94% and remained there. The decision was made to give him Regen-COV. The patient was not vaccinated against COVID-19.

Individualized Plan of Care

Regen-COV 1200mg (casirivimab 600mg and imdevimab 600mg) was given subcutaneously using four injection sites and

administering 2.5 ml per site. The patient was asked to remain in a supine position for 10 minutes post injection to decrease the amount of irritation to the injection sites. He was monitored for one hour post injection with no change in vital signs or evidence of any adverse reaction to treatment. The patient was sent home with his wife, an oxygen saturation monitor and educational materials. He was instructed to do his deep breathing exercises every hour while awake.

The following afternoon I called the patient to reassess. He reported that his fever was resolving and had been no higher than 100 degrees since that morning. He reported feeling weak but not short of breath. His oxygen saturation was 94%. He felt like he was improving.

The patient was also called 48 hours after receiving monoclonal antibody treatment and reported, ¨I am sure you saved my life with that medicine. ¨ He was afebrile, and his oxygen saturation was 97%. He reported fatigue but his malaise was resolved. He reported no irritation at the injection sites and was instructed to follow up with his physician if his symptoms returned or worsened. I spoke to him one week post injection and he reported a full recovery and returned to work.

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Pharmacokinetics

Pharmacokinetics explain what the body does to the drug in terms of absorption, distribution, metabolism and excretion. (Rosenthal and Burchum, 2018). Regen-Cov is lab-created human antibodies given in combination (Food and Drug Administration, 2021).

Regen-COV has a half-life of 26-30 days and is degraded into small peptides and amino acids in the body. It is not metabolized by the liver or kidneys. Because of this, patient weight, hepatic or renal impairment do not affect exposure of the drug or require dose modification. It is also very unlikely that Regen-COV will interact with other medications (Deeks, 2021).

Pharmacodynamics

Pharmacodynamics is the study of the effects of the drug on the body and how the effects are produced (Rosenthal and Burchum, 2018. pp 22-23). Regen-COV antibodies have a high affinity for the spike protein of the COVID-19 virus. The antibody binds to the spike protein and prevents the virus from binding to human cells. This reduces the viral replication in the lungs and other body tissues (Deeks, 2021).

References 

Deeks, E.D. (2021, October 30). Casirivimab/Imdevimab: First Approval. Nature Public Health Emergency Collection, 81(17), 2047-2055. doi:10.1007/s40265-021-01620-z.

Food and Drug Administration. (2021). U.S. Food & Drug Administration. Retrieved from FDA.gov:

FDA.gov/drugs/drug-safety-and-availability/fda-authorizes-regen-cov-monoclonal-antibody-

Therapy.

Rosenthal, L.D., & Burchum, J.R. (2021). Lehneś Pharmacotherapeutics for Advanced Practice Nurses

And Physician Assistants. St. Louis: Elsevier.

Discussion: Pharmacokinetics and Pharmacodynamics week 1

Pharmacokinetics and Pharmacodynamics

Pharmacokinetics and pharmacodynamics are an essential part of understanding drug efficacy. Meanwhile, pharmacokinetics deals with the study of the effect of a drug on the body through absorption, distribution, metabolism and excretion. pharmacodynamics addresses how the drug affects the body. The objective of pharmacokinetics is to improve medication efficacy and decrease drug toxicity while benefiting from the therapeutic results. Due to the correlation of the concentration of the drug in the body and the effect of the medication on the body, prescribers are called upon to monitor the usefulness of the medication. This has therefore, make pharmacokinetics and pharmacodynamics very important in medicine (Arcangelo, Peterson, Wilbur, & Reinhold, 2017). In order to understand the effect of drug pharmacokinetics and pharmacodynamics in patients this discussion focuses on explaining how this disease influences the effect of drugs on the body.

Patient is 16year old morbidly obese Native American female with a history of uncontrolled diabetes type  II and depression. She came with her mom to the pediatric clinic because she was presented with lower abdominal pain for one week. In the evaluation process, the urine laboratory showed high levels of protein in the urine. Patient was admitted to the pediatric unit for treatment.

Plan of care

If the patient’s condition is observed, diabetes is a major contributing factor to her problem. In addition, the fact that she is in renal failure, which makes the treatment problematic, needs the doctor to consider the doses of medication. Following the pharmacokinetic and pharmacodynamic function, diabetes must be closely monitored. The pharmacokinetics of drugs are affected by the body’s ability to absorb, distribute, metabolize and eliminate the drug from the system. Diabetes is also a condition that damages the body’s ability to carry out its normal functions. The prescription of medications for this patient has a lot to do with her diabetic disease process that may be the cause of kidney disease. Prescribers will have to carefully consider the effect of the disease on the drugs reaching their therapeutic level, as well as the elimination process. The half-life of drugs will be an essential tool for prescribing.

Factors impacting pharmacokinetics

Effect of absorption : increase in extracellular glucose affects membrane permeability and drug bioavailability.

Effect of distribution : The binding and affinity of albumin is impaired, due to the presence of high levels of glucose that glycate along with hemoglobin. The presence of free fatty acids also decreases the binding capacity of albumin.

Effect of metabolism : Most drugs are metabolized in the liver, but in the diabetic Mellitus condition, there is a decrease in CYP 3A4.

Effect on excretion : an increased rate of glomerular infiltration is observed in patients with diabetes mellitus. Microvascular and macrovascular changes are observed in patients with uncontrolled diabetes.

Pharmacodynamics

These medications, such as metformin, decrease hepatic glucose production, decrease intestinal glucose production, and increase peripheral glucose production and utilization.

Regular examinations for cardiovascular disease, liver function tests, evaluation of the kidneys should be carried out by the patient.

To conclude, the fact that diabetes patients turn to take more medication than nondiabetic patient, understanding the pharmacokinetics and pharmacodynamics of their medication will help providers prescribe safe medication to their patient (Dostalek, Akhlaghi, & Puzanovova, 2012).

Reference 

Amir Houshang, M. V. (2015). Effect of diabetes mellitus on the metabolism of drugs and toxins. Journal of Clinical Toxicology, 05(02). doi:10.4172/2161-0495.1000233

Arcangelo, V. P., Peterson, A. M., Wilbur, V., & Reinhold, J. A. (2017). Pharmacotherapeutics for advanced practice: A practical approach (4th ed.). Ambler, PA: Lippincott Williams & Wilkins.

Dostalek, M., Akhlaghi, F., & Puzanovova, M. (2012). Effect of diabetes mellitus on pharmacokinetic and pharmacodynamic properties of drugs. Clinical Pharmacokinetics, 51(8), 481-499. doi:10.2165/11631900-000000000-00000

Elbarbry, F., & Tran, M. (2016). Influence of diabetes mellitus on pharmacokinetics of drugs. MOJ Bioequivalence & Bioavailability, 2(1). doi:10.15406/mojbb.2016.02.00016

            Pharmacokinetics and pharmacodynamics are important when managing the health of patients. Pharmacokinetics is defined as the study of drug movement throughout the body (Rosenthal and Burchum, 2021). It consists of four processes including absorption, distribution, metabolism, and excretion. These processes can have an effect on the therapeutic management of drug therapy in patients. Pharmacodynamics is the study of biochemical and physiologic effects on the body and the molecular mechanisms by which these effects are produced (Rosenthal and Burchum, 2021). The results of these effects are based on the time and intensity of the therapeutic effects, as well as the occurrence of adverse drug reactions.  There are several factors that can influence the pharmacokinetics and pharmacodynamic processes, including age, gender, ethnicity, behavior, genetics, and disease processes.  It is important for the health care provider to have an understanding of pharmacokinetics and pharmacodynamics and its influence on drug therapy in order to develop an effective the plan of care for patients.

One previously worked as a home care nurse and took care of K.S. in her home. K.S. is a 70-year-old, African American female who was recently discharged from the hospital after undergoing a tricuspid valve repair. K.S. medical history includes right-sided heart failure, hypertension, hepatitis C, and ascites of the liver. K.S. was diagnosed post-surgery with chronic kidney disease, hypotension, and atrial fibrillation. K.S. discharge instructions were to include continuing taking previous medications prescribed along with midodrine and warfarin. K.S. was unsure of why she was taking certain medications, if and when her blood pressure should be checked, blood pressure parameters when taking midodrine and other prescribed hypertensive medications, the daily of dosage of warfarin and when laboratory testing needed to be completed to check PT/INR. K.S. observed to be frail in statue and was ordered Ensure three times per day.

Age along with pathophysiologic changes related to disease are huge factors that can affect pharmacokinetics and pharmacodynamic processes. According to Rodrigues, Herdeiro, Figueiras, Coutinho, and Roque (2020), ageing is a process that inevitable resulting in a decline in functioning and increased susceptibility to certain diseases, requiring the use of an increased amount of medication. Ageing can affect the distribution, metabolism, and excretion in the process of pharmacokinetics. Changes in body mass and protein synthesis can affect distribution of a drug and nutritional status can affect the rate of metabolism of a drug in an ageing patient (Rodrigues et. al, 2020). Most drugs are eliminated through kidneys. In the ageing patient, there is a decline in renal function related to a decrease in the glomerular filtration rate and renal blood flow, which makes it difficult for drugs to be excreted through the kidneys. This, in turn, puts the patient at risk for adverse drug reactions. According to Ponticelli, Sala, and Glassock (2015), older patients who have kidney disease are most at risk for adverse drug reactions. The process of pharmacodynamics affected by ageing can cause drug sensitivity and impaired homeostasis.

The patient K.S. has several medical conditions, resulting in a numerous amount of prescribed medications. She is frail in statue and has a lean body mass, which can affect the distribution of the medications prescribed. She, also, has poor nutritional status, which can affect the metabolism of the medications prescribed. She has been recently diagnosed with chronic kidney disease, which can affect elimination of the medications prescribed. She is prescribed warfarin, in which the response can be increased due to drug sensitivity leading to an adverse event. Also, due to impaired homeostasis, blood pressure regulation could be affected.

In developing a personalized plan of care for patient K.S., one has to take into consideration the patient’s age and medical history. One would review the drug therapy with the patient and discontinue any medications that are not necessary, have drug interactions, or put the patient at risk for an adverse drug reaction. One would ensure that current laboratory testing has been completed and review the laboratory results with the patient. Based on these results, one would consider medications that are safer for the patient and has the lowest effective dose possible. One would provide education to the patient on disease processes, purpose of medications prescribed, checking blood pressure and parameters to follow. One would stress the adherence to medication regimen and the importance of laboratory testing.

References

Ponticelli, C., Sala, G., and Glassock, R. (2015). Drug management in the elderly adult with

chronic kidney disease: a review for the primary care physician. Mayo Clinic Proc., 90

(5). Doi.org/10.1016/j.mayocp.2015.01.016.

Rodrigues, D., Herdeiro, M., Coutinho, P., and Roque, F. (2020). Elderly and polypharmacy:

physiological and cognitive changes. Frailty in the Elderly.

Doi:10.5772/intecopen.92122.

Rosenthal, L.D. and Burchum, J.R. (2021). Lehne’s pharmacotherapeutics for advanced practice 

nurses and physician assistants (2nd ed.). St. Louis, MO: Elsevier.

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.

Resources

Be sure to review the Learning Resources before completing this activity.
Click the weekly resources link to access the resources.

WEEKLY RESOURCES

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 Reply button to complete your initial post. Remember, once you click on Post Reply, you cannot delete or edit your own posts and you cannot post anonymously. Please check your post carefully before clicking on Post 

Case Scenario

J.M is a 72-year-old male with a diagnosis of alcohol induced dementia. Medical history, epilepsy, degenerative spine, and arthritis. The patient lives alone since the death of his wife two years ago. Since that time patient has been drinking two pints of alcohol daily according to his sister. Patient was admitted to the geriatric behavioral health unit after being found in his home by sister laying in feces and urine.  Sister reports an increase in agitation, fatigue, and confusion. Current medications include Keppra 500 mg twice daily PO, Lorazepam 2 mg at bedtime PO, and Haldol 2 mg twice daily PO.  All medications were verified with patients’ pharmacy.

Patient was admitted on the geriatric behavioral health unit where he became verbally and physically aggressive with staff, in fear of patient hurting himself or someone else the provider ordered a onetime IM injection of Haldol 0.5 mg, and lorazepam 1 mg IM.  An order for a 1:1 sitter was also ordered for the patients’ safety. Musculoskeletal disorders such as degenerative spine and arthritic conditions are the most common cause of chronic pain in the elderly. (Chau, 2008) Nothing was given for pain at this time due to the risk of more confusion, and falls due to sedation that could be caused by the IM Haldol and Lorazepam that was given for agitation.

Pharmacokinetics is the study of drug movement throughout the body which includes absorption, distribution, metabolism, and excretion. (Rosenthal, 2021) Pharmacodynamics is the study of the biochemical and physiologic effects of drugs on the body and the molecular mechanisms by which those effects are produced. (Rosenthal, 2021) In older adults with dementia, H2-receptor antagonists remain on the list of medications to avoid due to increased risk of cerebrovascular accident and greater rate of cognitive decline. (American Geriatrics Society 2019 updated AGS Beers Criteria Update Expert Panel., 2019) Benzodiazepines increase the risk of falls, and fractures in older adults that could lead to death.

The plan of care for the patient includes q4 vital signs, continuous monitoring by 1:1 staff. Assessing for sedation and adverse reactions to antipsychotic medication.  Assessing for pain and ordering CIWA’s q 4 hours to assess for alcohol withdrawals. Therapist consultation to address the patient’s grief and living arrangements after discharge.  Consult with a Geriatrician for pain management. Liver panel test would be performed to assess liver function.

References

American Geriatrics Society 2019 updated AGS Beers Criteria Update Expert Panel. (2019). Journal of the American Geriatrics Society, 67(4), 674-694.

Chau, D. L. (2008). Opiates and elderly: use and side effects. Clinical intervention in aging, 3(2), 273-278.

Rosenthal, L. D. (2021). Lehne’s pharmacotherapeutics for advanced practice nurses and physician assistants. St. Louis, MO: Elsevier.