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Chapter 11

Chapter 11. Drug Therapy in Geriatric Patients. Geriatric Patients. Disproportionately high prescription drug use exists in the elderly. 12% of Americans are age 65 years or older. This 12% consumes 31% of prescribed drugs.

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Chapter 11

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  1. Chapter 11 Drug Therapy in Geriatric Patients

  2. Geriatric Patients • Disproportionately high prescription drug use exists in the elderly. • 12% of Americans are age 65 years or older. • This 12% consumes 31% of prescribed drugs. • Geriatric patients experience more adverse drug reactions and drug-drug interactions than younger patients do.

  3. Geriatric Patients • Altered pharmacokinetics • More sensitive to drugs than younger adults and have wider variation • Multiple and severe illnesses • Severity of illness, multiple pathologies • Multiple-drug therapy • Excessive prescribing • Poor adherence

  4. Geriatric Patients • Individualization of treatment is essential. • Each patient must be monitored for desired and adverse responses. • Regimen must be adhered to. • Goal of treatment • Reduce symptoms and improve quality of life. • Cure is generally impossible.

  5. Outline of Drug Therapy in Geriatric Patients • Pharmacokinetic changes in the elderly • Pharmacodynamic changes in the elderly • Adverse drug reactions and drug interactions • Promoting adherence

  6. Pharmacokinetics: Absorption • Altered GI absorption is not a major factor in drug sensitivity. • Percentage of an oral dose that is absorbed does not change with age. • Rate of absorption may slow. • Delayed gastric emptying and reduced splanchnic blood flow occur.

  7. Pharmacokinetics: Distribution • Increased percentage of body fat • Storage depot for lipid-soluble drugs • Decreased percentage of lean body mass • Decreased total body water • Distributed in smaller volume; thus concentration is increased and effects are more intense • Reduced concentration of serum albumin • May be significantly reduced in the malnourished • Causes decreased protein binding of drugs and increase in levels of free drugs

  8. Pharmacokinetics: Metabolism • Hepatic metabolism declines with age. • Reduced hepatic blood flow, reduced liver mass, and decreased activity of some hepatic enzymes occur. • Half-life of some drugs may increase, and responses are prolonged. • Responses to oral drugs (those that undergo extensive first-pass effect) may be enhanced.

  9. Pharmacokinetics: Excretion • Renal function undergoes progressive decline beginning in early adulthood. • Reductions in renal blood flow, glomerular filtration rate (GFR), active tubular secretion, and number of nephrons • Drug accumulation secondary to reduced renal excretion is the most important cause of adverse drug reactions in the elderly.

  10. Pharmacokinetics: Excretion • Renal function should be assessed with drugs that are eliminated primarily by the kidneys. • In elderly patients • Use creatinine clearance, not serum creatinine, because lean muscle mass (source of creatinine) declines in parallel with kidney function. • Creatinine levels may be normal even though kidney function is greatly reduced.

  11. Pharmacodynamic Changes in the Elderly • Alterations in receptor properties may underlie altered sensitivity to some drugs. • Drugs with more intense effects in the elderly • Warfarin, certain CNS depressants • Beta blockers less effective in the elderly, even in the same concentrations • Reduction in number of beta receptors • Reduction in the affinity of beta receptors for beta receptor blocking agents

  12. Adverse Drug Reactions • Seven times more likely in the elderly • Account for 16% of hospital admissions • Account for 50% of all medication-related deaths • Majority are dose related, not idiosyncratic • Symptoms in elderly often nonspecific • Dizziness, cognitive impairment

  13. Predisposing ADR Factors • Drug accumulation secondary to reduced renal function • Polypharmacy • Greater severity of illness • Multiple pathologies • Greater use of drugs that have a low therapeutic index (eg, digoxin) • Increased individual variation secondary to altered pharmacokinetics • Inadequate supervision of long-term therapy • Poor patient adherence

  14. Measures to Reduce ADRs • Take thorough drug history, including OTCs. • Consider pharmacokinetic and pharmacodynamic changes due to age. • Monitor clinical response/plasma drug levels. • Use the simplest regimen possible. • Monitor for drug-drug interactions. • Periodically review the need for continued drug therapy. • Encourage patient to dispose of old meds. • Take steps to promote adherence and avoid drugs on the Beers list.

  15. Promoting Adherence with Unintentional Nonadherence • Simplified drug regimens • Clear, concise verbal and written instructions • Appropriate dosage form • Clearly labeled and easy-to-open containers • Daily reminders • Support system • Frequent monitoring

  16. Intentional Nonadherence • Most cases (75%) of nonadherence are intentional. • Reasons include • Expense, side effects, patient’s conviction that the drug is unnecessary or the dosage is too high

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