NURS 6521 STUDY GUIDE
Week 1 Discussion
Pharmacokinetics and pharmacodynamics are important factors in the plan of care for any
patient population. When taking care of elderly patients and prescribing medications, it is important for
healthcare prescribers to know how medications will affect elderly patients. One example of the
importance of pharmacokinetics and pharmacodynamics playing a factor in patient care was during the
treatment of a 75-year-old white female. She was forgetful and lived alone will little outside help for
daily task and healthcare. This patient used acetaminophen (Tylenol) for pain on a regular basis to treat
her arthritis and generalized pain. During a detailed history, she reported that she was careful not to
exceed the recommended daily dose of acetaminophen. Additional medications taken by this patient
included digoxin for an apparent cardiac condition. The patient presented with nausea, vomiting and
abdominal pain that was sudden in onset. Acetaminophen, a safe and effective pain reliever, is one of
the most popular OTC pain relivers in the U.S. Elevated LFTs and renal function labs provided clues to
the healthcare provider that drug toxicity may be present.
Pharmacokinetics is defined as the study of the time course of drug absorption, distribution,
metabolism, and excretion (Spruill et al., 2014). Clinical pharmacokinetics is the application of
pharmacokinetic principles to the safe and effective therapeutic management of drugs in an individual
patient (Spruill et al., 2014). Pharmacodynamics refers to the relationship between drug concentration at
the site of action and the resulting effect, including the time course and intensity of therapeutic and
adverse effects (Pea, 2012). The effect of a drug present at the site of action is determined by that drug’s
binding with a receptor.
Normal aging of organs and systems leads to diminished function in many areas including
decreased neuromuscular strength and reaction time to losses in memory and cognition (Jankovic, Illic,
Bukumiric & Jankovic, n.d.). There is a decreasing trend in hepatic metabolizing capacity with advancing
years that can affect the ability to clear therapeutic drugs and environmental chemicals. This factor,
combined with decreased renal clearance, causes prolonged retention of numerous drugs in elderly
individuals. The elderly consume a disproportionate quantity of drugs, with those older than 65 taking,
on average, two to six prescribed and one to three nonprescription drugs at any one time (Cecilia et al.,
2018). About 70 to 80% of an oral dose of digoxin is absorbed, mainly in the proximal part of the small
intestine (Martin-Suarez et al., n.d.). The degree of binding to serum albumin is 20 to 30% (Martin-
Suarez et al., n.d.). Digoxin is extensively distributed in the tissues, as reflected by the large volume of
distribution. High concentrations are found in the heart and kidneys, but the skeletal muscles form the
largest digoxin storage.
Polypharmacy is the administration of numerous drugs, usually more than five medications, to a
single patient (Jankovic, Illic, Bukumiric & Jankovic, n.d.). This practice is very common in elderly
individuals and increases the risks for drug interaction and side effects. In addition, there are numerous
pharmacodynamic factors in the CNS of elderly subjects that may affect sensitivity to neuroactive
agents. Changes in central cholinergic pathways, including decreased number of brain acetylcholine
postsynaptic receptors, have been demonstrated in rodent models of aging and may contribute to the
progressive decline in memory and cognition in elderly individuals (Pea, 2012). Liver function is generally
considered to be maintained well into old age. A variety of drugs can induce hepatotoxicity with the
possibility that
