Week 2 Assignment Due on Day 7 – Utilize the following Case Study:
Patient AO has a history of obesity and has recently gained 9 pounds. The patient has been diagnosed with hypertension and hyperlipidemia. Drugs currently
prescribed include the following:
Atenolol 12.5 mg daily
Doxazosin 8 mg daily
Hydralazine 10 mg qid
Sertraline 25 mg daily
Simvastatin 80 mg daily
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. Pharmacology System Essay Paper
Pharmacology: Cardiovascular System
Patient AO has obesity and has been diagnosed with hypertension and hyperlipidemia. They are currently taking atenolol, hydralazine, doxazosin, sertraline, and simvastatin. The factor that has been chosen and that will influence pharmacokinetics (PK) and pharmacodynamics (PD) of the above medications is age. As one grows older, there is a reduction in the efficiency of physiological processes in the body. The effects of the wear and tear make the body be especially sensitive to the pharmacodynamic actions of drugs. The same is true for pharmacokinetics. The liver of an older person is less efficient than that of a younger person. For this reason, a normal dose of a drug for a young person may prove to be excessive in the case of an older person. This is because the enzymes that break down the drug in the liver are less efficient in old age. The purpose of this paper is to explain how the factor of age might influence PK and PD of the drugs in the case of patient AO.
How Age Influences Pharmacokinetic and Pharmacodynamic Processes
As one ages, the liver also ages. This also means that the first pass metabolic mechanism through which medications are chemically broken down in the liver by the cytochrome P450 enzyme family reduces in efficacy. The effect of this is that there is greater bioavailability of oral medications after oral administration because their breakdown is slowed. The active drug accumulates in the body while its inactive metabolite remains low in blood concentration (Katzung, 2018; Rosenthal & Burchum, 2018). Renal function is also known to decline with age as the estimated glomerular filtration rate (eGFR) progressively drops with age (Hammer & McPhee, 2018; Huether & McCance, 2017). For this reason the pharmacokinetic action of excretion through the kidneys is compromised in older persons. The drug to be excreted and its metabolites then accumulate to dangerous levels in the body. The two medications that patient AO is taking and that might suffer this fate are hydralazine and atenolol (Katzung, 2018; Rosenthal & Burchum, 2018).
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Yet another pharmacokinetic factor affected by age is absorption of oral medications. In older persons, absorption of substances from the gastrointestinal tract reduces. This is because of the normal deterioration in physiological processes alluded to in the introduction above. Oral medications are also affected in the same way. The result is lower concentration levels of the drug in the plasma since most of it has not been absorbed. There may therefore be a necessity to alter the dosage upwards in some cases to achieve therapeutic concentrations (Katzung, 2018; Rosenthal & Burchum, 2018). Pharmacology System Essay Paper The other factor is lean body mass which is less in an older person. The distribution of some of the medications is dependent on lean body mass. In the case of patient AO, this is exacerbated by the fact that they are also obese with excess adipose tissue. This further increases the deficiency of lean body mass.
The effect of age on the pharmacodynamics of these medications is more complicated. For instance, atenolol as a beta-blocker inhibits the actions of epinephrine on the heart and the blood vessels. With age, the physiological effect of epinephrine on the heart and blood vessels is not as effective. This means that just a small dose of atenolol is enough to produce a therapeutic effect on an older person. The same is the case with doxazosin that acts at the post-synaptic receptors. In the case of hydralazine, vascular smooth muscle in an older person is rigid and calcified to some extent and so its peripheral vasodilation effect is lowered. Pharmacology System Essay Paper
Effect on Recommended Drug Therapy
Obesity and hyperlipidemia are managed by both lifestyle changes and medications (Rubenfire, 2018). However, the changes in the pharmacokinetics and pharmacodynamics of the medications that patient AO has due to the factor of age may require dose alterations. For instance, the selective serotonin reuptake inhibitor (SSRI) sertraline (Zoloft) causes weight gain by encouraging the synthesis of cholesterol. With advancing age there is less and less of lean body mass and therefore this pharmacodynamic action of sertraline may worsen obesity and hyperlipidemia. The dose must therefore be reduced in an older person (Armstrong, 2014). The dosages of hydralazine and atenolol will also need reduction in an older person due to the effect of age on renal function (a low eGFR). The dosages of simvastatin and doxazosin may be left as they are because there is no scholarly evidence suggesting that their PK and PD are affected significantly by the factor of age. Actually, doxazosin through its PD actions is effective in controlling obesity in older persons (Katzung, 2018; Rosenthal & Burchum, 2018).
How to Improve the Patient’s Drug Therapy Plan
Improving patient AO’s drug therapy plan will require adjustments in the dosages of the medications that he is on. The justification for this – as has been seen above – is that age affects the body’s normal physiological processes. Pharmacodynamics relies on the body’s normal physiology. Failure to do this will result in severe adverse effects caused by accumulation of medications and their metabolites because either metabolism in the liver of excretion by the kidneys is compromised (Fowler & ANA, 2015). Lastly, the polypharmacy that patient AO is on currently is not advisable. Improving the drug therapy plan will also therefore necessitate cutting out some of the medications altogether, especially those that perform the same function such as atenolol and hydralazine. One should be chosen over the other.
References
Armstrong, C. (2014). JNC 8 guidelines for the management of hypertension in adults. American Family Physician, 90(7):503-504. https://www.aafp.org/afp/2014/1001/p503.html
Fowler, M.D.M., & American Nurses Association. (2015). Guide to the Code of Ethics for Nurses with interpretive statements: Development, interpretation, and application, 2nd ed. Silver Spring, MD: American Nurses Association.
Hammer, D.G., & McPhee, S.J. (Eds). (2018). Pathophysiology of disease: An introduction to clinical medicine, 8th ed. New York, NY: McGraw-Hill Education.
Huether, S.E. & McCance, K.L. (2017). Understanding pathophysiology, 6th ed. St. Louis, MO: Elsevier, Inc.
Katzung, B.G. (Ed) (2018). Basic and clinical pharmacology, 14th ed. New York, NY: McGraw-Hill Education.
Rosenthal, L.D., & Burchum, J.R. (2018). Lehne’s pharmacotherapeutics for advanced practice providers. St. Louis, MO: Elsevier.
Rubenfire, M. (2018). 2018 AHA/ACC Multi-society guideline on the management of blood cholesterol. American College of Cardiology. Retrieved 9 March 2020 from https://www.acc.org/latest-in-cardiology/ten-points-to-remember/2018/11/09/14/28/2018-guideline-on-management-of-blood-cholesterol Pharmacology System Essay Paper