Pharmacokinetics, Pharmacodynamics and the Aging Process
As the body ages the decline in function of body systems affects the way that drugs are absorbed, metabolized, and excreted. This creates a challenge for healthcare providers to appropriately provide treatment to the older adult as they need to be cognizant of these changes and their effect. This might also have a negative effect on the older adult as they may experience severe side effects or not gain full therapeutic effect of the drug. This can lead to nonadherence of medication regimen in the older population.
The way drugs are absorbed, metabolized, and excreted by the body changes with aging due to a slowing down of bodily functions pertaining to the systems that perform these functions. According to Meiner & Yeager (2018) In order for a drug to be absorbed it must travel from the site of administration into the systemic circulation. Absorption of drugs in the older adult is affected by decreased gastric acid secretion, slowing down of peristalsis within the gastrointestinal tract, slowed gastric emptying, and decreased subcutaneous fat related to aging. These changes alter the way and how long it takes a drug to be absorbed into the body.
As per Meiner & Yeager (2018) Metabolism is the transformation of drugs into smaller molecules that are easier for the body to excrete. Metabolism in the elderly is only affected by alterations due to the aging process if it involves the hepatic system. First pass metabolism is when drugs are absorbed from the intestine and enter the hepatic circulation where a portion is metabolized before entering the systemic circulation. In the older adult the hepatic blood flow decreases this can lead to a decrease in drugs metabolized in the hepatic system. This can create drug toxicity in the older adult due to a greater number of drugs entering the systemic circulation at a slower pace therefore extending the half life and increasing the risk of drug buildup.
Excretion is the removal of drugs from the body that happens mainly through the kidneys. With aging renal function decreases which means it takes a longer period to get rid of the body’s byproducts. This can have a negative effect on the excretion of drugs as the slowing down of the renal system will slow down the excretion of drugs also. This can increase the half life of the drug and create greater accumulation in the body which can lead to toxicity.
The use of salt substitutes in the older adult should be done with caution as this can lead to life threatening events due to an increase in potassium level. Older adults who consume salt substitutes are usually those who have hypertension or heart failure they do this to decrease blood pressure. Use of salt substitutes containing potassium chloride is a potential strategy to reduce sodium intake, increase potassium intake, and thereby lower blood pressure and prevent the adverse consequences of high blood pressure, (Greer et al.,2019). The use of salt substitutes with certain medications such as: potassium sparing diuretics, angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and nonsteroidal anti-inflammatory drugs has the potential to cause hyperkalemia in the older adult.
Medication nonadherence in the elderly is a challenge for the healthcare professional to overcome as there are many factors that can contribute to this. In order for the nurse to promote compliance with medication regime he or she must assess the patient for risk factors such as : socioeconomic status, alterations in cognition, functional status, health literacy, cultural ideals regarding medications, and side effects experienced that might deter the older adult from adhering to the regimen. The nurse should provide teaching in a language that is understood by the patient, create a schedule that is not complicated and that does not interfere with the patient’s daily activities. Promote the use of drugs that are acceptable to the persons culture, encourage use of drugs that have the risk of less severe side effects, and encourage the patients to use the same pharmacy to fill prescriptions. For those with financial issues the nurse can educate them on programs that provide coupons, pharmacies that offer low price generic drugs, or patient assistance programs.
Greer, R. C., Marklund, M., Anderson, C. A., Cobb, L. K., Dalcin, A. T., Henry, M., & Appel, L. J. (2019). Potassium-Enriched Salt Substitutes as a Means to Lower Blood Pressure. Hypertension,75(2). doi:10.1161/hypertensionaha.119.13241
Meiner, S., & Yeager, J. J. (2019). Gerontologic nursing (6th ed.). Elsevier.
Therapeutic drug monitoring is usually used to assist doctors with monitoring and maintaining drugs within the therapeutic range. The therapeutic window refers to the concentration degree whereby a medication applies its clinical impact with insignificant unfavorable impacts. Therapeutic drug monitoring is typically helpful in observing medications that get utilized for long-term conditions or medications with a limited therapeutic range (Prso et al., 2020). Some medications have peak and trough levels which are used to screen the accomplishment of the therapeutic concentration (peak) and medication clearing to keep away from toxicity (trough). Therapeutic drug monitoring is also essential in distinguishing and monitoring drug interactivity and to recognize poor adherence as a cause of poor treatment reaction. It is imperative to note that every medication’s pharmacokinetics may differ from the victims’ age, weight, clinical status, and sex.As an individual’s age increases, drug absorption gets affected by aging gastrointestinal mucosa and decreased gastric acid production from 25 to 20 percent. Due to the weakening of the gastrointestinal movements in aged people and low gastric emptying rate, drugs may stay for a longer period in the gastrointestinal tract, which is favorable for slow drug absorption. In drug metabolism, aging reduces the liver’s parenchymal cells and decreased blood flow in the liver which impacts the liver’s capability to efficiently carry out drug metabolism. As one becomes older, liver enzymes decrease and the half-life of taken drugs gets prolonged. The kidney, which is the primary organ utilized in drug excretion, reduces its functionality as an individual becomes older (Gujjarlamudi, 2016). Therefore, the younger generation generally has a greater drug excretion rate than the elderly, whereby toxic drug reactions are more prone in older adults.Potassium-sparing diuretics such as spironolactone, triamterene, and amiloride can cause hyperkalemia. However, the risk increases when these potassium-sparing diuretics get used together with salt substitutes and potassium supplements. The danger of hyperkalemia in conjunction with spironolactone elevates by threefold if taken together with potassium supplements. The usage of concurrent loop diuretics hardly guarantees the occurrence of hyperkalemia. Potassium supplements need to be avoided in the individuals being treated with potassium-sparing diuretics. Also, the utilization of immunosuppressants such as tacrolimus and ciclosporin in conjunction with potassium-sparing diuretics or the aldosterone antagonists increases hyperkalemia risks (Maideen, 2020). Various groups of people are at high risk of getting hyperkalemia. These include patients suffering moderate to serious renal insufficiency, hypoaldosteronism, and other illnesses related to adverse reactions to aldosterone’s potassium secretory impacts. Hypoaldosteronism is frequently found in older patients with persistent renal impairments or diabetic nephropathy, or even those suffering from an adrenal disease.Education levels, dosing frequency, explanation of the medications, health-related issues, and satisfaction with the patient’s counseling are factors associated with medication adherence and compliance. While preventing medication non-adherence in older adults, patients should take their medications as directed by physicians (Zhao et al., 2019). However, a patient’s literacy may contribute to the wrong administration of drugs. The use of reminder packaging or pillboxes can help to prevent forgetting drug administration by patients. Pharmacists and physicians have to consider older adults’ characteristics like educational background and unique patient’s health-related issues to explain treatment and assure that patients understand their counseling.
ReferencesGujjarlamudi, H. B. (2016). Polytherapy and drug interactions in elderly. Journal of Mid-Life Health, 7(3), 105. https://doi.org/10.4103/0976-7800.191021. (Links to an external site.)Maideen, N. M. P. (2020). Pharmacologically Relevant Drug Interactions of Potassium-Sparing Diuretics. J Pathol Toxicol Res, 1(1), 1-4.Prso, K., Zidekova, N., Dohal, M., Porvaznik, I., Prso, M., Kertys, M., & Mokry, J. (2020). Benefits of Therapeutic Drug Monitoring of First Line Antituberculosis Drugs. Acta Medica Martiniana, 20(2), 45–55. https://doi.org/10.2478/acm-2020-0006. (Links to an external site.)Zhao, Y.-Y., Dang, F.-P., Zhai, T.-T., Li, H.-J., Wang, R.-J., & Ren, J.-J. (2019). The effect of text message reminders on medication adherence among patients with coronary heart disease. Medicine, 98(52), e18353. https://doi.org/10.1097/md.0000000000018353 (Links to an external site.).
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