DRUGS IN GERIATRICS

Dr AZZA ELSHERBINYAssistant professor of pharmacology

By the end of this lecture the student should be able to describe:

1-The changes in physiological functions in elderly

2-The changes in pharmacokinetics in elderly3-Pharmacodynamics changes in elderly4-Drug interactions in elderly5-Changes in drug effects in elderly6-Adverse drug reactions in the elderly7-Practical aspects of geriatric pharmacology

GENERAL CONSIDRATIONS1-An increasing number of adults ≥65 years are living with

multiple health problems2-There are more women than men among older

population.3-Among all persons ≥65 years of age, the five leading

causes of death are heart diseases, cancer, stroke, chronic obstructive pulmonary diseases,

influenza and diabetes4-There is high incidence of adverse effects in elderly due

to polypharmacy, reduced drug elimination, multiple disease states and ↑ drug sensitivity

5-Other problems in elderly are patient compliance, memory changes, hear loss and ↓ vision

PHARMACOKINETIC CHANGES IN THE ELDERLY

-Physiological changes associated with aging, diseases and pharmacological factors can affect pharmacokinetic parameters.

These changes can alter drug response

Absorption:

Can be affected due to physiological changes:-

1-Delayed gastric emptying rate2-↑ Gastric pH 3-↓ splanchnic blood flow4-↓ absorptive surface5-Impaired intestinal motility

Disease states:- e.g.

1-Achlorhydria2-Diarrhea3-Gastrectomy4-Malabsorptive syndromes5-Pancreatitis

Pharmacological factors:- e.g.

1-Drug interactions2-Antacids3-Anticholinergics4-Cholstyramine5-Food

DistributionPhysiological changesWhat is the effect of the changes in serum albumin and

in body fats on drug distribution?1-↓ cardiac output2-↓ total body water3-↓Lean body mass4-↓ Serum albumin5-↑ α1-acid glycoprotein6-↑ body fatQUIZE:-What is the effect of the changes in serum albumin on

drug distribution?

Disease states

1-CHf2-Dehydration3-Edema4-Ascites5-Hepatic failure6-Malnutrition7-Renal failure

Pharmacological Factors

1-Drug-drug interactions2-Protein binding(displacement) can you

provide examples?

Metabolism

1-↓ Hepatic mass2-↓ Enzyme activity 3-↓ Hepatic blood flowExplain the following, ↓ enzyme activity at

old age?

Disease states

1-CHF2-Hepatic failure3-Malignancy4-Malnutrition5-Thyroid disease6-Viral infection

Pharmacological Factors

1-Alcohol2-Smoking3-Induction of metabolism4-Inhibition of metabolismExplain the effects of both enzyme induction

and inhibition on drug response?

ExcretionPhysiological changes1-↓ Renal blood flow2-↓ GFR3-↓ Tubular secretion4-↓ Renal mass↓renal elimination↑adverse effects of drugs (drugs

eliminated by kidney)Drugs highly dependent on renal function for

elimination(Aminoglycosides, acetazolamide, allopurinol, amantadine,

amiloride, atenolo, cephalosporines,Clonidine, fluconazole, H2 antagonists,

enalapril……………………………etc…)

PHARMACODYNAMICS CHANGES IN THE ELDERLY

These changes due to inefficient homeostatic adjustments or

receptors sensitivity

HomeostasisOrthostatic or postural hypotension occurs as a result of

impaired baroreceptor functionAnd a failure of cerebral blood flow auto regulation. Can be

aggravated by1-Sympatholytics2-Volume-depleting drugs and vasodilating agentsThese can contribute to falls in blood pressure.Most common drugs which are used and produce interfere

with homeostasis1-TCAS:- hypotension,and has other side effects such as

tremors, cardiac arrhythmias, sedation2-Antihypertensive;- most of them causes postural

hypotension

Impaired in coordination in old age-Benzodiazepines and sedative hypnotics:-

sedation, weakness, ↓ coordination, confusion

-Narcotic analgesics:- sedation, ↓ coordination, confusion

-Antipsychotics:- sedation, extra pyramidal effects

Receptor sensitivity changes can lead to exaggerated response (e.g.

nitrazepam, heparin, warfarin)1-A decline in the dopamine system ↑

sensitivity to dopamine blocking agents(e.g. neuroleptics, metoclopramide)

2-Cholinergic deficits in the central nervous can ↑ susceptibility to confusion caused by ant-cholinergic

AgentsWhat are the drugs that can induce

confusion in older patients?

ADVERSE DRUG REACTIONS IN THE ELDERLY1-Studies have shown that the percentage of

patients with adverse reactions↑ from about 10%

When a single drug is being taken nearly 100% when ten drugs are taken

2-What are the other reasons for high incidence of errors in prescribed drugs?.

DRUG-DRUG INTERACTIONS

-Enzyme inhibitors:-e.g.Cimetidine(H2 blocker) inhibits the hepatic

metabolism of many drugs including phenytion

Mention other drugs are affected by liver enzyme activity?

-Enzyme inducersWhat are the enzyme inducers, explain

their effect on other drugs?

PRACTICAL ASPECTS OF GERIATRIC PHARMACOLOGY

Drug therapy has considerable potential for both helpful and harmful effects in elderly

This balance may be tipped in the right direction by adherence to a few principles

1-Take a careful drug history, why? (Drug-drug interaction, drug induce disease, drug

Treating disease)2-Prescribe only for a specific indication and real

need of the drugs

PRACTICAL ASPECTS OF GERIATRIC PHARMACOLOGY

3-Define the goal of drug therapy, start small dose and increase gradually

Wait at least 3 half-lives of the drug, until reach the expected response (why),

If no improvement↑ dose if no response shift to a different drug

4-Maintain a high index of suspicion regarding drug reactions and interactions in elderly

5-Simplify the regimen as much as possible (↓ number of drugs being taken,

Collect the drugs that can be taken at same time of the day)