gero chapter 9

7/28/2019 Gero Chapter 9

1/9

GERO CHAPT 9

Geropharmacology:

Persons 65 years and older are the largest users of prescription and OTC medications. Theyconsume about one third of all prescription drugs and one half of available OTC. The most

commonly prescribed and used drugs in the ambulatory older populations are cardiovasculardrugs, diuretics, nonopioid analgesics, anticoagulants, and antiepileptic. Gastrointestinalpreparations and analgesics are the most used OTC medications, followed by cough products,

eye washes, and vitamins.

Pharmacokinetics:

It is the study of the movement and action of a drug on the body. It determines the concentration

of drugs in the body, which in turn determines effect. The concentration of drug at different

times depends on:

Absorption; this is how the drug is taken into the body. A drug must first be absorbed into

the bloodstream for it to be effective. The amount of time between the administration of

the drug and its absorption depends on these factors

a. Route of administration: most common are intravenous, oral, enteral, parental,

transdermal and rectal.

Drug is delivered immediately to the bloodstream with intravenous,

quickly through parental, transdermal, and rectal routes. Orally and

rectally administered drugs are absorbed the most slowly and primarily in

the small intestine.

Liquid drug dosage forms for oral use come as solutions, suspensions,

tinctures, and elixirs.

Solid oral drug dosage forms are tablets, capsules, powders and pills.

Factors affecting the rate at which a medication is dissolved are the

amount of liquid in the stomach, the type of coating the tablet has, the

extent of tablet compression used in making the tablet, the presence of

expanders in the tablet, the solubility of the drug in the acid environmentof the stomach, and the rate of peristalsis.

Presence of food in the stomach may or may not delay absorption

b. Bioavailability: the degree to which a drug or other substance becomes available

to the target tissue after administration.


2/9

c. The amount of drug that passes through the absorbing surfaces in the body.

Effects of aging process on drug absorption:

1. Diminished salivary secretion and esophageal motility may interfere with

swallowing some medications.

2. Decreased gastric acid, common in the elderly will retard the action of acid-

dependent drugs.

3. Delayed stomach emptying may diminish or negate the effectiveness of short-

lived drugs that could become inactivated before reaching he small intestine.

4. Some enteric-coated medications which are specifically meant to bypass the

stomach may be delayed so long in the older adults that their actions begin in the

stomach and may produce undesirable effects such as gastric irritation or nausea.

5. Slowed intestinal motility, frequently seen with aging, can increase the contact

time and increase drug effect because of prolonged absorption, significantly

increasing the risk for adverse reactions or unpredictable effects

6. Drugs that are extensively metabolized as they pass through the liver are said to

have a large first-pass effect. Such drugs usually require much larger oral doses

than the same drug given by injection. Normally, the liver mass and blood flow

decreases significantly as one ages resulting to reductions in the metabolism rate

with potential but unknown implications.

7. Drying of the mouth is a common side effect of many of the medications taken byolder adults and it may reduce or delay buccal absorption on the older adults. In

such cases, rectal administration may be useful.

Transdermal Drug Delivery System (TDDS):

a. Used for topical application of drugs such as nitroglycerin

b. Has developed significantly and is now used for many fat-soluble drugs, usually a

medication-impregnated patch (e.g. estrogen, nicotine, fentanyl, and nitroglycerin).

c. Overcomes any first-pass problems

d. Is more convenient, acceptable and reliable than other routes especially in the outpatient

setting and for some persons with cognitive disorders

e. Provides more constant rate of drug administration and eliminates concern about

gastrointestinal absorption variation, gastrointestinal intolerance, and drug interaction.


3/9

f. The skin must be intact, the patch must remain in place for the designated amount of

time, and the previous patch must be removed before a new one is applied.

g. The characteristic thinning, dryness, and roughness of older skin may affect absorption of

the intended dose.

h. It is indicated when a slow, time-release delivery into the tissue and the bloodstream is

desired.

i. The risk for an allergic reaction to the patch is increased with the normal immune

changes with aging.

Distribution:

The systemic circulation transports a drug throughout the body to receptors on the

cells of the target organ, where a therapeutic effect is initiated

Organs of high blood flow (brain, kidneys, lungs, liver) rapidly receive the highest

concentrations.

Distribution to organs of lower blood flow (skin, muscles, fat) occurs more slowly

and results in lower concentrations of the drug in these tissues

Lipophilic (fat-soluble drugs pass through capillary membranes more easily than do

hydrophilic (water-soluble) drugs, resulting in more rapid tissue distribution and a

greater volume of distribution.

Decrease body water in normal aging leads to higher serum level of water-solubledrugs.

Drugs that are highly lipid soluble are stored in the fatty tissue, thus extending and

possibly increasing the drug effect, depending on the level of adiposity.

Distribution also depends on the availability of plasma protein in the form of

lipoproteins, globulins, and especially albumin.

Some drugs are bound to protein for distribution.

Normally, a predictable percentage of the absorbed drug is inactivated as it is bound

to the protein.

The remaining free drug is available in the bloodstream for therapeutic effect when an

effective concentration is reached in the plasma.

Metabolism:


4/9

Some drugs exert their therapeutic effect in their absorbed form while others must be

metabolized first.

Metabolism is the process wherein the chemical structure of the drug is converted to a

metabolite that is more easily used and excreted (a process called biotransformation).

As long as a drug remains in its original state or as an active metabolite (s), it will

continue to exert a therapeutic effect.

Excretion:

Drugs and their metabolites are excreted either unchanged or as metabolites.

A few drugs are eliminated through the lungs, as unreabsorbed metabolites in bile and

feces, or in breast milk.

Very small amounts of drugs and metabolites can also be found in hair, sweat, tears,and semen.

Glomerular filtration depends on both the rate and the extent of protein binding of the

drug.

The process involves passive filtration and only unbound drugs are filtered.

Because kidney function declines in many older persons, so does the ability to excrete

or eliminate drugs in a timely manner. The glomerular filtration rate, renal plasma

flow, tubular function, and reabsorptive capacity decline.

Pharmacodynamics:

o Refers to the physiological interactions between a drug and the body, specifically, the

chemical compounds introduced into the body and the receptors on the cell membrane.

o Receptors are generally specifically configured cellular proteins that, because of their

shape and ionic charge, bind to specific chemicals in the medications.

o The receptor protein has a specific shape that fits the chemical molecule, like a glove to a

hand with complementary ionic charges.

o When the chemical binds to the receptor, the therapeutic effect is initiated.

o Drugs are usually similar in configuration to chemicals naturally occurring in the body

such that they bind to the same receptor sites.


5/9

o Although the drugs are designed to bind to specific receptor sites for specific purposes,

usually they will attach to various other types or receptors as well.

o The result might be unwanted effects.

o The older a person gets, the more likely he or she will have altered and unreliablepharmacodynamics.

o It is not always possible to explain or predict the alteration, several are unknown.

o Those of special note in the elderly are related to drugs with anticholinergic side effects

which significantly increase the risk for accidental injury and associated with geriatric

syndromes.

o Baroreceptor reflex responses decrease with age.

o This causes increased susceptibility to positional changes (orthostatic hypotension) andvolume changes (dehydration).

Polypharmacy:

Defined as the use of medications, or as the use of multiple medications for the same

problem.

It is extremely common among older adults and a source of potential morbidity and

mortality.

May be necessary if the patient has multiple chronic conditions

May occur unintentionally

Is exacerbated by the combination of a high use of specialists and a reluctance of

prescribers to discontinue potentially unnecessary drugs that have been prescribed by

someone else; therefore treatments are continued longer than necessary.

Two major concerns of polypharmacy are the increased risk for drug interactions and the

increased risk for adverse events.

Drug Interactions:

The more medications that one takes the greater the possibility that one or more of them

will interact with each other, a dietary supplement, or other herbal preparation.

The more chronic conditions one has, the more likely that a medication for one condition

will affect the body in such a way as to influence the other.


6/9

When two or more medications are given at the same time or closely together, the drugs

may potentiate one another, that is when given together the drugs have stronger effects

than when give alone, or

When two or more medications are given at the same time or closely together, the drugs

may antagonize each other, that is when give together one or the more of the drugsbecome ineffective.

Drug-supplement/Drug-herb Interactions:

Are the potential interactions of the herbal preparations or nutritional supplements.

Because of inadequate labeling requirements, drug interactions may not be listed on the

product labels of these supplements.

Drug-food Interactions:

Foods may interact with drugs, producing increased, decreased, or variable effects.

Foods can bind to drugs affecting their absorption.

Certain drugs antagonize the therapeutic action of a drug.

Drug-drug Interactions:

Made common due to the polypharmacy that may be a necessary part of health care in

later life.

When several medications are crushed, mixed together, and then dissolved in water for

administration, a new product is created and drug-drug interactions may have already

begun.

Several drugs may compete to simultaneously bind and occupy the receptor sites needed

by the other drug, creating varied bioavailability of one or both of the drugs.

Interference with enzyme activity may alter metabolism and cause drug deficiencies or

toxicities.

Altered distribution may be caused by displacement of one drug from its receptor site by

another drug.

Altered metabolism can occur when one drug increases (inducts) or decreases (inhibits)

the metabolism of another drug.

Adverse Drug Reactions (ADR):


7/9

Occur when there is a noxious response to a drug.

Ranges from a minor annoyance to death and are common causes of hospitalization,

especially for persons more than 80 years of age.

Such medication categories include cardiovascular agents, diuretics, nonopioipanalgesics, hypoglycemic, and anticoagulants (especially anticoagulants).

Sometimes they can be predicted from the pharmacological effects of the drug such as in

bleeding form coagulants, other times they are unpredictable such as in an allergic

reaction to antibiotics.

Allergic reactions become more common in the older adults as the immune system

changes, many drug reactions are deemed serious, may even be fatal, and most of them

are preventable.

To minimize the likelihood of ADR, the dose can be slowly increased until it safely

reaches a therapeutic level.

Implications for Gerontological Nursing:

i. The nurse is the key person in ensuring that the medication used is appropriate, effective,

and as safe as possible.

ii. The nurse is knowledgeable about drug interactions and signs ans symptoms of ADR.

iii. The nurse promotes the actions necessary to prevent drugs from becoming toxic and to

treat toxicity promptly.

iv. The nurse initiates assessment of medication use, evaluate outcomes, and provide the

necessary teaching.

Assessment:

o The initial step in ensuring that drug use is safe and effective is to conduct a

comprehensive drug assessment.

o Brown bag approach is the gold standard of assessment in a medicine history.

o The nurses analysis of the assessment data is centered on identifying unnecessary or

inappropriate medications, establishing safe usage, determining the patients self-

medication management ability, monitoring the effect of current medications and other

products and evaluating effectiveness of any education provided.

Education:


8/9

Most common intervention used to promote medication adherence.

The nurse should;

Find out who manages the persons medications, help the person, or assist with

decision-making; and with the elders permission, make sure that the helper ispresent when any teaching is done.

Minimize distraction, and avoid competing with television or others demanding

the patients time; make sure the person is comfortable and is not hungry, thirsty,

tired, too warm or too cold, in pain, or in need of the toilet.

Provide the teaching during the best time of the day for the person.

Ensure that you will be understood.

Encourage the person to use techniques which have worked in the past or developnew strategies to ensure correct and timely medication use when needed.

Psychotherapeutics in Later Life:

Antidepressants: Selective serotonin reuptake inhibitors (SSRIS) have been found to be

highly effective antidepressants. They are the drugs of choice for first-line use in older

adults. Most adults are sensitive to it while some are not.

Anxiolytic agents: drugs developed to treat anxiety. Examples are benzodiazepines and

buspirone (BuSpar).

Antipsychotics (Neuroleptics): are tranquilizing medications used primarily to treat

psychoses and off-label as mood stabilizers fro bipolar disorder.

o Movement disorders

Acute dystonia: an acute dystonia reaction is an abnormal involuntary

movement consisting of a slow and continuous muscular contraction or

spasm

Akathisia: is a compulsion to be I motion, a sense of restlessness, beingunable to be still, having an unrelenting desire to move, and feeling like

crawling out of my skin. The patient is seen pacing, fidgeting, and

markedly restless.

Parkinsonian symptoms: the use of antipsychotics may cause a collection

of symptoms that mimic Parkinsons disease. A bilateral tremor (as

opposed to unilateral tremor in true Parkinsons), bradykinesia, and


9/9

rigidity may be seen, which may progress to the inability to move. The

patient may have inflexible facial expression and appear bored and

apathetic and be mistakenly diagnosed as depressed.

Tardive dyskinesia: Irreversible movement disorder that occurs when

antipsychotics have been used continuously for at least 3 6 months.Symptoms appear as wormlike movements of the tongue; other facial

movements include grimacing, blinking, and frowning. Slow, maintained,

involuntary, twisting movements of the trunk, limbs, neck, face, and eyes.

No treatment reverses its effect.

gero chapter 9

Documents