Transcript Chapter_011
Chapter 11 Drug Therapy in Geriatric Patients Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 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. Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 2 Geriatric Patients Altered pharmacokinetics Multiple and severe illnesses Severity of illness, multiple pathologies Multiple-drug therapy More sensitive to drugs than younger adults and have wider variation Excessive prescribing Poor adherence Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 3 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. Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 4 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 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 5 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. Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 6 Pharmacokinetics: Distribution Increased percentage of body fat Decreased percentage of lean body mass Decreased total body water Storage depot for lipid-soluble drugs 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 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 7 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. Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 8 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. Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 9 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. Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 10 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 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 11 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 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 12 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 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 13 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. Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 14 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 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 15 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 Copyright © 2013, 2010 by Saunders, an imprint of Elsevier Inc. 16