As individuals age, the body undergoes several physiological changes that can affect the way medications are handled. These changes can influence drug absorption, distribution, metabolism, and elimination. Understanding how our bodies handle medications as we age is essential for healthcare providers to ensure appropriate and safe medication use among older adults. Here are some ways in which the body’s handling of medications may change with age:

1. Absorption:

• Gastrointestinal Changes: Aging can lead to reduced gastric acid secretion and decreased blood flow to the gastrointestinal tract, potentially affecting the absorption of certain medications.
• Slower Gastric Emptying: The rate at which the stomach empties its contents may slow down, prolonging the time required for medications to be absorbed.

2. Distribution:

• Changes in Body Composition: With aging, there is a shift in body composition, characterized by an increase in body fat and a decrease in muscle mass. This change can affect the distribution of medications, as certain drugs tend to distribute more in lean body tissues.
• Altered Protein Binding: Aging may lead to changes in the levels and binding capacities of plasma proteins, such as albumin. Medications that are highly protein-bound may exhibit altered distribution in the body.

3. Metabolism:

• Hepatic Metabolism: The liver’s ability to metabolize medications may decline with age due to reduced liver mass, blood flow, and enzyme activity. This can lead to a decrease in drug metabolism and potential accumulation of medications in the body.
• Phase I and Phase II Enzyme Activity: Aging can affect the activity of specific drug-metabolizing enzymes, such as cytochrome P450 enzymes. This alteration can result in changes in the metabolism of certain medications.

4. Elimination:

• Renal Function: Age-related changes in kidney function, including decreased glomerular filtration rate (GFR) and renal blood flow, can impact the elimination of medications primarily excreted by the kidneys. This can result in the prolonged half-life and increased risk of drug accumulation and toxicity.
• Renal Tubular Secretion: The process of renal tubular secretion, responsible for the elimination of certain medications, may also be impaired in older adults, further affecting drug clearance.

5. Pharmacodynamics:

• Increased Sensitivity: Older adults may exhibit increased sensitivity to medications due to changes in receptor sensitivity, altered neurotransmitter activity, and decreased compensatory mechanisms. This increased sensitivity can lead to enhanced drug effects or an increased risk of adverse reactions.

It is important to note that these changes in medication handling can vary among individuals, and not all older adults will experience them to the same extent. Healthcare providers should consider these age-related changes and individual variations when prescribing and monitoring medications for older patients. Regular assessment of renal and hepatic function, along with close monitoring for adverse drug reactions, can help optimize medication regimens for older adults and ensure safe and effective treatment outcomes.

References

Bencivenga, L., De Souto Barreto, P., Rolland, Y., Hanon, O., Vidal, J. S., Cestac, P., Vellas, B., & Rouch, L. (2022). Blood pressure variability: A potential marker of aging. Ageing research reviews, 80, 101677. https://doi.org/10.1016/j.arr.2022.101677

Brivio, P., Paladini, M. S., Racagni, G., Riva, M. A., Calabrese, F., & Molteni, R. (2019). From Healthy Aging to Frailty: In Search of the Underlying Mechanisms. Current medicinal chemistry, 26(20), 3685–3701. https://doi.org/10.2174/0929867326666190717152739

Cohen, R. A., Marsiske, M. M., & Smith, G. E. (2019). Neuropsychology of aging. Handbook of clinical neurology, 167, 149–180. https://doi.org/10.1016/B978-0-12-804766-8.00010-8

Cho, S. J., & Stout-Delgado, H. W. (2020). Aging and Lung Disease. Annual review of physiology, 82, 433–459. https://doi.org/10.1146/annurev-physiol-021119-034610

Cruz-Jimenez M. (2017). Normal Changes in Gait and Mobility Problems in the Elderly. Physical medicine and rehabilitation clinics of North America, 28(4), 713–725. https://doi.org/10.1016/j.pmr.2017.06.005

Fang, Y., Gong, A. Y., Haller, S. T., Dworkin, L. D., Liu, Z., & Gong, R. (2020). The ageing kidney: Molecular mechanisms and clinical implications. Ageing research reviews, 63, 101151. https://doi.org/10.1016/j.arr.2020.101151

Frontera W. R. (2017). Physiologic Changes of the Musculoskeletal System with Aging: A Brief Review. Physical medicine and rehabilitation clinics of North America, 28(4), 705–711. https://doi.org/10.1016/j.pmr.2017.06.004

Jakovljevic D. G. (2018). Physical activity and cardiovascular aging: Physiological and molecular insights. Experimental gerontology, 109, 67–74. https://doi.org/10.1016/j.exger.2017.05.016

Khan, S. S., Singer, B. D., & Vaughan, D. E. (2017). Molecular and physiological manifestations and measurement of aging in humans. Aging cell, 16(4), 624–633. https://doi.org/10.1111/acel.12601

Lee, Y. I., Choi, S., Roh, W. S., Lee, J. H., & Kim, T. G. (2021). Cellular Senescence and Inflammaging in the Skin Microenvironment. International journal of molecular sciences, 22(8), 3849. https://doi.org/10.3390/ijms22083849

Lobo, F., Haase, J., & Brandhorst, S. (2022). The Effects of Dietary Interventions on Brain Aging and Neurological Diseases. Nutrients, 14(23), 5086. https://doi.org/10.3390/nu14235086

Lorenzo, E. C., Kuchel, G. A., Kuo, C. L., Moffitt, T. E., & Diniz, B. S. (2023). Major depression and the biological hallmarks of aging. Ageing research reviews, 83, 101805. https://doi.org/10.1016/j.arr.2022.101805

Müller, L., Di Benedetto, S., & Pawelec, G. (2019). The Immune System and Its Dysregulation with Aging. Sub-cellular biochemistry, 91, 21–43. https://doi.org/10.1007/978-981-13-3681-2_2

Neves, J., & Sousa-Victor, P. (2020). Regulation of inflammation as an anti-aging intervention. The FEBS journal, 287(1), 43–52. https://doi.org/10.1111/febs.15061

Zhang, X., Meng, X., Chen, Y., Leng, S. X., & Zhang, H. (2017). The Biology of Aging and Cancer: Frailty, Inflammation, and Immunity. Cancer journal (Sudbury, Mass.), 23(4), 201–205. https://doi.org/10.1097/PPO.0000000000000270