Chapter 6

Drug Therapy in the Elderly

Chapter Outline:

Introduction

Pharmacokinetic Changes

Absorption

Distribution

Metabolism

Excretion

Pharmacodynamic Changes

Polypharmacy

Adverse Drug Reactions

Noncompliance

Causes of noncompliance

Medication Management

Pharmacokinetic Changes

Pharmacokinetics is the study of how drugs travel through the body over time. It deals with all aspects of drug disposition in the body, including absorption from the administration site, distribution into various body compartments, hepatic metabolism to active & inactive metabolites, & excretion of parent drug & metabolites from the body.

Changes Affecting Drug Disposition in the

ElderlyPharmacokinetic Parameter Physiological Change

Absorption Gastric pHGastric Emptying Time

GI motilityGI blood flow

Distribution Lean muscle massTotal Body Fat

Total body waterSerum AlbuminCardiac Output

Metabolism Liver massHepatic blood flowEnzyme activity

Excretion Renal Blood FlowGlomerular filtration rateRenal tubular function

Pharmacodynamic Changes:

Pharmacodynamics refers to the action of drugs, or the biological effects resulting from the interaction between drugs & its receptor site.

Age-related pharmacodynamic changes in the elderly can greatly influence drug response, usually leading to increased sensitivity or an exaggerated pharmacological response to a given drug.

Pharmacokinetic Parameter

Absorption

Distribution

Metabolism

Excretion

Polypharmacy:Polypharmacy refers to the use of multiple medications in one individual.They may be needed but the term polypharmacy usually connotes the use of more drugs than are needed.

Polypharmacy:

As the number of medications taken increases, the likelihood of adverse drug reactions & drug-drug interactions also increases.

As the complexity of the drug regimen increases, the risk of noncompliance increases.

Reasons for Polypharmacy:

number of chronic illnesses or physical ailments; a lack of one primary health provider to coordinate medical care & drug use, subsequent use of multiple physicians (specialists), use of multiple pharmacies, & self-treatment, primarily with over-the-counter drugs.

Elderly take an average of 2.8 drugs per day

Nursing homes=3.4 /day;hospitalized=9/day

Adverse Drug Reactions:Any unexpected, unintended, undesired, or excessive response to a drug when it is used in the approved manner. They typically:Require a modification in drug therapy (drug discontinuation or dosage change)Cause or prolong admission to the hospitalRequire supportive treatmentNegatively affect prognosis & may result in disability or death.

Adverse Drug Reaction Risk Factors:

An increased number of chronic illnesses.

Severity of illnesses

Pharmacokinetic changes

Pharmacodynamic changes

Polypharmacy

Observed Drug Reactions:

Delirium

Confusion

Lethargy

Fatigue

Arrhythmias

Nausea, vomiting

Incontinence

Tremor

Tardive dyskinesia

Pseudoparkinsonism

Visual/hearing disturbances

Hypotension

Syncopal attacks,falls

Constipation,diarrhea

Electrolyte abnormalities

Urinary retention

Noncompliance:

Medication compliance has been defined as the extent to which a patient’s behavior coincides with a prescriber’s planned medical regimen.

Any deviation from this is, obviously, noncompliance.

1.8 billion prescriptions written each year are taken incorrectly. Up to 90% is due to patients taking too little medication.

Factors associated-poor compliance:

Female gender

Low socioeconomic status

Solitary living

Lack of a support person

Cognitive impairment

Drug costs

Multiple disease states

Physical disabilities

Complex drug regimens

Polypharmacy

Poor communication

Causes of Noncompliance:

Polypharmacy & Complex Drug Regimens

Physical Disabilities

Poor Communication

Cognitive Impairment

Drug Costs

Medication Management:With every new complaint or symptom the drug regimen should be reviewed to identify any adverse drug reactions or rule out drug toxicity. Adverse reactions are often completely reversible-when source removed.

Drug Therapy in the Elderly:

Offers tremendous benefits to elderly people when used appropriately.

Periodic review of medication regimens must be done, so that elderly patients receive maximal benefits from drug therapy while minimizing potential adverse outcomes.