Medication in the Elderly

INTRODUCTION TO PHARMACOLOGY

Course Information

  • Course Code: 722.544

  • Topic: Medication Therapy for Older Adults

PHARMACOKINETICS & PHARMACODYNAMICS IN AGING

  • Discussion Points:

    • Alterations in pharmacokinetics (the movement of drugs within the body) and pharmacodynamics (the effects of drugs on the body) due to aging.

    • Physiological and anatomical effects of aging impacting medication therapy outlook.

    • Nursing challenges associated with assessment and medication administration for older adults, including:

    • Polypharmacy (the concurrent use of multiple medications).

    • Adverse drug reactions (ADRs).

    • Medication errors.

    • Medication adherence.

    • Key strategies to promote safe and effective medication administration for older individuals.

    • Individual responsibilities of nurses/caregivers regarding medication administration.

    • Relevant legislation governing medication use in aged care settings.

AGING DEMOGRAPHICS

Age Classifications:

  • Young-old: 65 - 74 years

  • Middle-old: 75 - 84 years

  • Old-old: >85 years

  • Frail elderly: >65 years with debilitating conditions

  • Important Note: There is significant variability in the rate of aging; age-related changes should not be conflated with disease-related changes.

Predicted Age Distribution

  • Population Statistics:

    • 1951-2061 projected age distribution shows a noticeable increase in the proportion of older adults.

    • Source: Statistics New Zealand

DRUG USAGE IN THE ELDERLY

  • Notable Statistics:

    • Individuals over 65 account for:

    • 12% of the population.

    • 31% of prescribed drugs usage.

    • Reasons for increased usage include:

    • Heightened chronic illness severity.

    • Multiple concurrent pathologies/chronic conditions.

    • Excessive prescribing trends.

    • 40% of over-the-counter (OTC) drug usage.

    • Greater frequency of adverse drug reactions (2 to 7 times more than younger adults).

    • Vulnerable to medication errors.

PHYSIOLOGICAL CHANGES WITH AGE

General Decline in Organ Function:

  • Body Composition Changes:

    • Decreased body water.

    • Reduced thirst sensation.

    • Increased body fat and decreased lean body mass.

    • Diminished plasma proteins (e.g., albumin).

Specific Organ Systems:

  • Gastrointestinal Tract:

    • Reduced motility and blood flow.

    • Decreased gastric acid secretion.

  • Liver:

    • Reduction in hepatic mass and blood flow.

    • Fewer microsomal enzymes leading to reduced first-pass metabolism.

  • Cardiovascular System:

    • Lower cardiac output, postural hypotension, and slower compensatory reflexes.

  • Renal System:

    • Decrease in kidney size, functional nephrons, blood flow, tubular secretion, and glomerular filtration rate (GFR decreases by 50% by age 75).

DRUG ACTIONS AND INTERACTIONS

Drug-Receptor Interactions:

  • Increased sensitivity of brain receptors makes psychoactive drugs more potent.

  • Less stable vascular nerve control; examples include excess drop in blood pressure from antihypertensives and heart rate slowing from medications like Digoxin.

Absorption:

  • Slower gastric emptying and gastrointestinal motility result in changes to drug absorption capacity.

  • Increased gastric pH and decreased active transport mechanisms also affect absorption.

Distribution:

  • Changes in body composition:

    • Increased fat reduces clearance of fat-soluble drugs.

    • Decreased lean body mass and body water concentration raises water-soluble drug concentration (e.g., digoxin).

    • Reduced plasma protein levels lower drug-binding sites and raise free drug levels in circulation.

Metabolism:

  • Metabolic rate decreases by 1/2 to 2/3 compared to young adults.

  • Altered hepatic function results in prolonged drug half-life due to reduced blood flow and enzyme activity.

Elimination:

  • Decreased GFR and renal blood flow result in reduced clearance for renally excreted drugs leading to a greater risk of accumulation and toxicity.

PHARMACOTHERAPY CONSIDERATIONS

Common Adverse Reactions in the Elderly:

  • Drug Classes and Possible Effects:

    • Beta Blockers: Risks include cardiac insufficiency, bradycardia, and falls.

    • Anticholinergics, Tricyclic Antidepressants, Phenothiazines: Risk of urinary retention, constipation, delirium, and postural hypotension.

    • Diuretics: Potential for dehydration and electrolyte disturbances.

    • Opioids: Risks involve respiratory depression, confusion, and constipation.

  • CNS Drugs: Dosage may need to be reduced to 50% of normal adult doses due to increased sensitivity.

Individualized Approach to Drug Therapy:

  • Importance of starting low doses and adjusting as needed to achieve optimal responses while monitoring for adverse effects.

  • “START LOW AND GO SLOW” guideline emphasized for all medications.

POLYPHARMACY & ITS IMPLICATIONS

  • Statistics:

    • Average 70-year-old takes approximately seven different medications; those over 85 average twelve.

    • 12% of older adult hospital admissions due to drug reactions.

  • Risks:

    • Drug accumulation due to renal function reduction.

    • Polyprescribing and inadequate supervision of medications.

    • Potentially avoidable medication admissions related to ADRs.

CHALLENGES IN MEDICATION MANAGEMENT

Common Behavioral Patterns:

  • Self-prescribing and misuse of medications.

  • Non-adherence resulting from:

    • Lack of understanding or cognitive declines.

    • Financial disadvantages or social isolation.

Recommendations for Managing Medications:

  • Conduct thorough drug history assessments.

  • Employ non-pharmacological approaches where feasible.

  • Simplify drug regimens to enhance adherence.

  • Regularly assess for potential drug interactions and reactions.

REGULATIONS IN AGED CARE

  • Key legislative frameworks in medication management and patient rights include:

    • Health Practitioners Competence Assurance Act 2003

    • Code of Health and Disability Services Consumers’ Rights

    • Health and Disability Commissioners Act 1994

    • Old Peoples Home Regulations 1987

CASE STUDY EXAMPLE

  • Scenario: John (88) concerned about medication safety after his wife appears dizzy from potential drug ingestion.

  • Discussion Point: Guidance for appropriate medication storage and administration education tailored for older adults.

REFERENCES

  • Brown, D. & Edwards, H. (Eds.). (2012). Lewis’s medical-surgical nursing - Assessment and management of clinical problems. (3rd ed.). Marrickville, NSW, Australia: Mosby Elsevier.

  • Bryant, B., Knights, K., Darroch, S. & Rowland, A. (2019). Pharmacology for health professionals. (5th ed.). Chatswood, NSW, Australia: Elsevier.

  • Crisp, J., Douglas, C., Rebeiro, G. & Waters, D. (Eds.). (2017). Potter & Perry’s fundamentals of nursing. (5e.). Chatswood, NSW, Australia: Elsevier.

  • Ministry of Health, New Zealand website: www.moh.govt.nz/olderpeople