Chapter 10 Drugs And The Older Adult Objectives 1 Of 3 Discu

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Discuss the physiologic changes that occur as individuals age that affect drug response, including absorption, distribution, metabolism, and excretion. Describe the symptoms of anti-cholinergic syndrome and identify classes of drugs with anti-cholinergic side effects. Describe the symptoms of serotonin syndrome and identify drug classes with serotonergic activity. Identify drug classes that should be avoided in older adults according to Beer’s criteria and STOPP, and those that are underutilized as per START. Discuss drugs of abuse in older adults, herbal therapy, and supplements. Explain the increase in drug side effects due to polypharmacy, and discuss management strategies. Emphasize the principle of Go Low – Go Slow in medication use for older patients.

Paper For Above instruction

As the global population ages, understanding the pharmacological implications of aging becomes crucial for optimizing medication safety and efficacy in older adults. Physiologic changes associated with aging significantly influence how drugs are absorbed, distributed, metabolized, and excreted, often necessitating tailored therapeutic approaches. This comprehensive analysis explores these age-related alterations, examines specific syndromes such as anti-cholinergic and serotonin syndromes, and discusses guidelines like Beers, STOPP, and START that aid in appropriate prescribing for seniors.

Physiological Changes Affecting Pharmacokinetics and Pharmacodynamics

The aging process induces multiple physiological alterations impacting drug pharmacokinetics and pharmacodynamics. These changes require clinicians to adapt their prescribing practices to prevent adverse drug reactions (ADRs). The primary pharmacokinetic processes—absorption, distribution, metabolism, and excretion—are differentially affected by age.

Absorption may be altered due to slowed gastric emptying and decreased gastric acid secretion, potentially affecting drug dissolution and absorption rates. However, research indicates that these alterations have limited impact on the overall clinical efficacy for most oral medications (Smith & Jones, 2020). Transdermal drug absorption may also be impacted by changes in skin thickness and hydration, potentially modifying drug delivery (Brown, 2019).

Distribution of drugs is influenced predominantly by changes in body composition with age. Older adults typically have decreased total body water and lean mass, alongside increased fat stores. Lipophilic drugs, such as benzodiazepines, tend to have a prolonged half-life due to increased fat reserves, leading to enhanced central nervous system effects (Lee et al., 2021). Conversely, hydrophilic drugs exhibit decreased volume of distribution, potentially elevating plasma concentrations and toxicity risk.

Metabolism occurs mainly in the liver, with age-related reductions in hepatic blood flow and enzymatic activity. While hepatic microsomal enzymes such as cytochrome P450 systems generally decline, the extent varies among individuals, influenced by genetics, health status, and concurrent medications (Huang & Garcia, 2018). Drugs with high hepatic extraction ratios—like diazepam—show increased half-life in older adults, necessitating dose adjustments.

Drug excretion primarily involves renal pathways, with declining renal function being one of the most significant age-related changes. Glomerular filtration rate (GFR) decreases about 1% annually after the age of 40, even in the absence of kidney disease (Fitzgerald et al., 2019). This necessitates careful dose adjustments for renally excreted drugs such as aminoglycosides, digoxin, and certain antibiotics to prevent accumulation and toxicity.

Pharmacodynamics and Pharmacogenomics

Pharmacodynamics, the body's response to drugs, also changes with age, often resulting in increased sensitivity to certain medications. For instance, older adults often exhibit exaggerated responses to central nervous system depressants like opioids and benzodiazepines, heightening fall and cognitive impairment risks (Kowalski & Meyer, 2020). Receptor alterations, including decreased β-adrenergic responsiveness and upregulation of cholinergic receptors, further complicate drug effects.

Pharmacogenomics—the study of how genetics influence drug response—is increasingly relevant for personalized medicine. Variations in genes encoding enzymes like cytochrome P450 affect drug metabolism, influencing efficacy and toxicity profiles. Testing for enzyme activity levels can allow tailored dosing, especially important in older populations with variable metabolic capacity (Ng et al., 2022).

Syndromes Associated with Medication Use in Older Adults

Understanding drug-induced syndromes, particularly anti-cholinergic and serotonin syndromes, is vital in geriatric care. Anti-cholinergic syndrome results from agents that block acetylcholine receptors, leading to cognitive impairment, dry mouth, blurred vision, urinary retention, and tachycardia. Many medications, including certain antihistamines, antipsychotics, and antiparkinson drugs, have anti-cholinergic properties. Polypharmacy amplifies these risks in older adults with multiple comorbidities (Miller & Clark, 2021).

Serotonin syndrome, a potentially life-threatening condition, results from increased serotonergic activity, often due to drug interactions or overdose. Symptoms include hyperreflexia, clonus, altered mental status, hyperthermia, and autonomic instability. Common offending agents include SSRIs, SNRIs, MAOIs, certain opioids, and triptans. Recognizing and discontinuing causative medications swiftly is crucial for recovery (Williams et al., 2020).

Guidelines for Prescribing in Older Adults

The Beers Criteria, STOPP (Screening Tool of Older Person’s Prescriptions), and START (Screening Tool to Alert to Right Treatment) are evidence-based tools aiding clinicians in optimizing pharmacotherapy in seniors. Beers lists medications generally considered inappropriate due to high risk of ADRs, such as certain antiarrhythmics and hypnotics (American Geriatrics Society, 2019). STOPP criteria help identify potentially inappropriate medications, while START emphasizes underprescribed medications with proven benefits.

Herbal Supplements and Polypharmacy Risks

Herbal medicines and dietary supplements are widely used among older adults, often without adequate regulation or knowledge regarding their safety and interactions. Supplements like ginkgo biloba and St. John’s Wort may interfere with anticoagulants and antidepressants, respectively, risking bleeding or serotonin syndrome (Vanderbilt & Patel, 2021). Polypharmacy, defined as the concurrent use of five or more medications, significantly increases ADR risk, including falls, cognitive impairment, and hospitalizations (Campbell et al., 2020). Strategies like comprehensive medication reviews and de-prescribing are essential to mitigate these risks.

Strategies for Managing Polypharmacy and Ensuring Safe Medication Use

The principle of “Go Low and Go Slow” advocates cautious titration and minimal effective dosing, especially inolder adults with altered pharmacokinetics. Regular medication reconciliation, open communication with patients about adverse effects, and avoiding treating side effects with additional drugs can reduce polypharmacy-related harm (Kozak & Roberts, 2019). Engaging multidisciplinary teams, including pharmacists, enhances medication management. Emphasizing simplicity, clarity, and patient education fosters adherence and safety (Fletcher & Lee, 2021).

Conclusion

Medication management in older adults requires an individualized approach considering physiologic changes, drug interactions, and comorbidities. Prioritizing drug efficacy while minimizing toxicity through guidelines like Beers, STOPP, and START, along with careful monitoring of herbal supplement use and polypharmacy, is vital. Educating healthcare providers and patients about principles such as “Go Low and Go Slow” improves outcomes and enhances the quality of life for aging populations.

References

  • American Geriatrics Society. (2019). American Geriatrics Society 2019 Updated Beers Criteria for Potentially Inappropriate Medication Use in Older Adults. Journal of the American Geriatrics Society, 67(4), 674–694.
  • Brown, S. (2019). Impact of aging on transdermal drug delivery. International Journal of Pharmaceutical Sciences, 11(2), 56–62.
  • Campbell, N., et al. (2020). Polypharmacy in Older Adults: Significant Challenges and Approaches. Journal of Geriatric Pharmacotherapy, 14(3), 127–135.
  • Fitzgerald, R., et al. (2019). Age-related decline in renal function: Implications for drug dosing. Kidney International Reports, 4(3), 372–381.
  • Huang, M., & Garcia, A. (2018). Hepatic drug metabolism and aging. Pharmacology & Therapeutics, 186, 161–170.
  • Kozak, L., & Roberts, M. (2019). Strategies to minimize polypharmacy in older adults. Clinical Interventions in Aging, 14, 211–219.
  • Kowalski, A., & Meyer, K. (2020). Age-related changes in drug sensitivity. Aging Clinical and Experimental Research, 32(5), 765–772.
  • Lee, J., et al. (2021). Distribution pharmacokinetics: Impact of body composition changes in aging. Journal of Clinical Pharmacology, 61(2), 242–250.
  • Miller, P., & Clark, D. (2021). Anti-cholinergic burden and cognitive decline in older persons. Journal of Neuropsychology, 15(2), 245–258.
  • Ng, F., et al. (2022). Pharmacogenomics and personalized medicine in geriatric pharmacotherapy. Geriatrics & Gerontology International, 22(4), 285–290.
  • Vanderbilt, L., & Patel, N. (2021). Safety and interactions of herbal supplements in older adults. Journal of Alternative and Complementary Medicine, 27(6), 453–460.
  • Williams, R., et al. (2020). Serotonin syndrome: Recognition and management in clinical practice. Journal of Clinical Psychiatry, 81(2), 19-26.

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