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the study of drug movement throughout the body.
The four basic pharmacokinetic processes are
absorption, distribution, metabolism, and excretion.
Pharmacokinetic processes determine the ______ of a drug at its sites of action and determine the time course over which drug responses take place.
To move throughout the body, drugs must cross cell membranes. They do this by:
- (1) passing through channels or pores
- (2) passing through the membrane with the aid of a transport system
- (3) penetrating the membrane directly
Which means of crossing the cell membrane is most common?
direct penetration of the membrane
- found in the liver, kidneys, placenta, intestines, and brain capillaries
- can transport a variety of drugs out of cells.
For most drugs, movement throughout the body depends on the ability to penetrate membranes directly, because:
- (1) most drugs are too large to pass through channels or pores
- (2) most drugs lack transport systems to help them cross cell membranes.
- A drug must be lipid soluble (lipophilic) to penetrate cell membranes directly.
Polar molecules dissolve in polar solvents (e.g., water) but not in nonpolar solvents (e.g., oil); therefore, polar drugs are:
unable to dissolve in the lipid bilayer of the cell membrane.
Acidic drugs ionize in basic (alkaline) media, whereas basic drugs ionize in acidic media. When a pH gradient exists between two sides of a membrane:
- Acidic drugs accumulate on the alkaline side.
- Basic drugs accumulate on the acidic side.
What is ion trapping?
By manipulating the urinary pH, ion trapping (pH partitioning) can be used to draw toxic substances from the blood into the urine, thereby accelerating their removal.
Absorption is defined as:
the movement of a drug from its site of administration into the blood.
Absorption is influenced by:
- the rate of drug dissolution
- surface area available for absorption
- blood flow at the site of administration
- lipid solubility of the drug
- pH partitioning.
The term parenteral
- is used to mean by injection
- The principal parenteral routes are intravenous, subcutaneous, and intramuscular.
Intravenous administration has several advantages:
- rapid onset of action
- precise control over drug levels in the blood
- the ability to use large volumes of fluid
- the ability to administer irritant drugs
Intravenous administration has several disadvantages:
- high cost
- the danger posed by irreversibility
- the potential for fluid overload
Intramuscular administration has two advantages:
- suitability for poorly soluble drugs
- suitability for depot preparations
Intramuscular administration has two disadvantages:
- the potential for discomfort
- Subcutaneous administration has the same advantages and disadvantages as intramuscular administration.
Oral administration has the advantages of:
ease, convenience, economy of administration, and safety
Oral administration has the disadvantages of:
- high variability in absorption
- possible inactivation of the drug
- the requirement for a conscious, cooperative patient
- the potential to cause local irritation to the gastrointestinal (GI) tract
Drug preparations are considered chemically equivalent if they contain
the same amount of the identical chemical compound (drug).
Preparations are considered equal in _______ if the drug they contain is absorbed at the same rate and to the same extent.
Two formulations of the same drug can be chemically equivalent but differ in their:
Enteric-coated oral formulations are designed to
release their contents in the small intestine, not in the stomach.
Sustained-release oral formulations are designed to
release their contents slowly, permitting a longer interval between doses.
Distribution is defined as:
drug movement from the blood to the interstitial space of tissues and from there into cells. The rate at which drugs are delivered to a particular tissue is determined by the blood flow to that tissue.
In most tissues, drugs can leave the vasculature simply by:
passing through pores in the capillary wall.
The term blood-brain barrier (BBB) refers to
the presence of tight junctions between the cells that compose capillary walls in the central nervous system.
To leave the blood and reach sites of action within the brain, a drug must be able to pass through cells of the capillary walls. Only drugs that are _____________ can cross the BBB to a significant degree.
lipid soluble or have a transport system
Drug movement across the placenta
The membranes of the placenta do not constitute an absolute barrier to the passage of drugs. The same factors that determine drug movements across all other membranes determine the movement of drugs across the placenta.
Many drugs bind reversibly to
- plasma albumin
- Drug molecules that are bound to albumin cannot leave the vascular system.
Increased levels of free drug (caused by competition for binding sites or albumin deficiency) _______ the intensity of drug responses ______________.
- and toxicity can result.
Drug metabolism (biotransformation) is defined as:
the enzymatic alteration of a drug’s structure.
Most drug metabolism takes place in the liver and is performed by:
- the hepatic microsomal enzyme system
- (also known as the P450 system).
Drug metabolism has six possible consequences of therapeutic significance:
- Accelerated renal excretion of drugs
- Drug inactivation
- Increased therapeutic action
- Activation of “prodrugs”
- Increased toxicity
- Decreased toxicity
The most important consequence of drug metabolism is:
the promotion of renal drug excretion.
Drug metabolism can:
- convert pharmacologically active compounds into inactive forms
- increase the effectiveness of drugs
- convert prodrugs into their active form in the body
- reduce toxicity by converting drugs into inactive forms
- increase the potential for harm by converting relatively safe compounds into toxic forms
Induction of drug-metabolizing enzymes by a drug can have two therapeutic consequences.
- (1) it can stimulate the liver to produce more drug-metabolizing enzymes, increasing the drug’s own rate of metabolism and necessitating an increased dosage to maintain therapeutic effects
- (2) it can accelerate the metabolism of other drugs used concurrently, necessitating an increase in their dosages
The term first-pass effect refers to:
the rapid inactivation of some oral drugs as they pass through the liver after absorption.
the movement of drugs and their metabolites out of the body.
Most drugs are excreted by _________, but drugs also may be excreted by ____________.
- the kidneys
- urine, bile, sweat, saliva, breast milk, and expired air.
Renal drug excretion has three steps:
- glomerular filtration
- passive tubular reabsorption
- active tubular secretion
In the kidneys, drugs that are lipid soluble undergo ______ from the tubule back into the blood
In the kidneys, drugs that are not lipid soluble (ions and polar compounds):
remain in the urine to be excreted.
Drugs taken by breast-feeding women:
can be excreted in the breast milk, thereby exposing the nursing infant to the drugs.
Drugs entering the intestine in bile:
- may undergo reabsorption back into the portal blood.
- This reabsorption, referred to as enterohepatic recirculation, can substantially prolong the presence of a drug in the body.
For most drugs, a direct correlation exists between:
therapeutic and toxic responses and the amount of drug present in plasma.
The minimum effective concentration
- is defined as the plasma drug level below which therapeutic effects do not occur.
The plasma level at which toxic effects begin is called:
the toxic concentration.
The therapeutic range of a drug lies:
between the MEC and the toxic concentration.
Drugs with a wide therapeutic range are ________, whereas drugs with a narrow therapeutic range are _____________.
- relatively easy to use safely
- difficult to use safely
The half-life of a drug is:
the time required for the amount of drug in the body to decrease by 50%.
Drugs with a short half-life must be administered:
more frequently than drugs with a long half-life.
When drugs are administered repeatedly:
their levels gradually rise and then reach a plateau (steady state).
When the amount of drug eliminated between doses equals the dose administered:
the average drug levels remain constant and a plateau will have been reached.
When a drug is administered repeatedly in the same dose, a plateau is reached
in approximately four half-lives.
As long as the dosage remains constant
the time required to reach a plateau is independent of the dosage size.
The highest level is referred to as
the peak concentration
The lowest level is referred to as
the trough concentration.
The acceptable height of the peaks and troughs depends on the drug’s
- therapeutic range
- the peaks must be kept below the toxic concentration, and the troughs must be kept above the MEC.
When a plateau must be achieved quickly, a large initial dose is administered. This is called:
a loading dose.
A plateau is maintained by administering
smaller doses, or maintenance doses.
Three techniques can be used to reduce fluctuations in drug levels:
- (1) administer drugs by continuous infusion
- (2) administer a depot preparation, which releases the drug slowly and steadily
- (3) reduce both the size of each dose and the dosing interval (keeping the total daily dose constant).
When drug administration is discontinued, most (94%) of the drug in the body is eliminated
over four half-lives.
the study of the biochemical and physiologic effects of drugs and the molecular mechanisms by which those effects are produced.
The dose-response relationship is:
- the response becomes progressively larger with increasing dosage.
Maximal efficacy is
the most intense effect a drug can produce.
A drug with a ___________ is not always more desirable than a drug with a ___________;
- very high maximal efficacy
- lower efficacy
- the intensity of the drug response must be matched to the patient’s needs.
Potency is defined as
- the amount of a drug that must be given to elicit an effect.
- Potency is rarely an important drug characteristic.
It is important to note that the potency of a drug implies nothing about its
- maximal efficacy.
- Potency and efficacy are completely independent qualities.
A receptor can be defined as
any functional macromolecule in a cell to which a drug binds to produce its effects.
Binding of a drug to its receptor usually is
The receptors through which drugs act are
normal points of control for physiologic processes.
Under physiologic conditions, receptor function is regulated by
molecules supplied by the body.
All that drugs can do at receptors is
mimic or block the action of the body’s own regulatory molecules.
Because drug action is limited to mimicking or blocking the body’s own regulatory molecules, drugs cannot
- give cells new functions.
- Rather, they can only alter the rate of preexisting processes.
Drugs produce their therapeutic effects by
helping the body use its preexisting capabilities to the patient’s best advantage.
In theory, it should be possible to synthesize drugs that can
alter the rate of any biologic process for which receptors exist.
The four primary families of receptors are:
- cell membrane–embedded enzymes
- ligand-gated ion channels
- G protein–coupled receptor systems
- transcription factors
Selective drug action is possible largely because
drugs act through specific receptors.
If a drug interacts with _____ receptor and if that receptor type regulates _______, the drug will have limited effects. Conversely, if a drug interacts with _______ receptor types, it is likely to elicit _____________.
- only one type of
- just a few processes
- several different
- a wide variety of responses
Selectivity does not
The simple occupancy theory of drug-receptor interaction states that
- (1) the intensity of the response to a drug is proportional to the number of receptors occupied by that drug
- (2) a maximal response will occur when all available receptors have been occupied.
The modified occupancy theory ascribes two qualities to drugs
affinity and intrinsic activity.
The term affinity refers to
the strength of the attraction between a drug and its receptor.
Drugs with high affinity are
The term intrinsic activity refers to
the ability of a drug to activate a receptor upon binding.
Drugs with high intrinsic activity have
high maximal efficacy.
Affinity and intrinsic activity are
Agonists are molecules that
In terms of the modified occupancy theory, agonists have both
- affinity and high intrinsic activity.
- Affinity allows them to bind to receptors, whereas intrinsic activity allows them to activate the receptor upon binding.
Antagonists produce their effects by
preventing receptor activation by endogenous regulatory molecules and drugs.
In terms of the modified occupancy theory, antagonists have
- affinity for receptors but no intrinsic activity.
- Affinity allows the antagonist to bind to receptors, but lack of intrinsic activity prevents the bound antagonist from causing receptor activation.
Because antagonists act by preventing receptor activation, if no agonist is present, administration of an antagonist has
no observable effect; the drug binds to its receptors, but nothing happens.
Antagonists can be subdivided into two major classes:
- noncompetitive antagonists
- competitive antagonists
- Most antagonists are competitive.
Noncompetitive antagonists bind
irreversibly to receptors
Competitive antagonists bind
reversibly to receptors
Partial agonists have _________ intrinsic activity
- only moderate
- therefore, their maximal efficacy is lower than that of full agonists.
When the receptors of a cell are continually exposed to an agonist, the cell
- usually becomes less responsive.
- When this occurs, the cell is said to be desensitized, or refractory, or to have undergone down-regulation.
Continuous exposure to antagonists
- causes the cell to become hypersensitive
- (also referred to as supersensitive).
Although the effects of most drugs result from drug-receptor interactions, some drugs do not act through receptors.
- Rather, they act through simple physical or chemical interactions with other small molecules.
- The dose required to produce a therapeutic response can vary substantially from patient to patient, because people differ from one another.
The nurse who appreciates the reality of interpatient variability is better prepared to
anticipate, evaluate, and respond appropriately to each patient’s therapeutic needs.
The average effective dose is
- the dose required to produce a defined therapeutic response in 50% of the population. It can be considered a “standard” dose.
After a patient’s response to this “standard” dose has been evaluated, subsequent doses can be
adjusted up or down to meet the patient’s needs.
At the ED50, some patients will be
undertreated, whereas others will have received more drug than they need.
Because drug responses are not completely predictable, the nurse must evaluate the patient to determine whether
too much or too little medication has been administered.
Because of variability in responses, nurses, patients, and other concerned individuals must evaluate actual responses and be prepared to inform the prescriber about these responses so that
proper adjustments in dosage can be made.
The therapeutic index, defined as the
- LD50:ED50 ratio
- is a measure of a drug’s safety. Drugs with a high therapeutic index are relatively safe. Drugs with a low therapeutic index are relatively unsafe.
Drug-drug interactions can occur whenever a patient
takes two or more drugs.
Some drug-drug interactions are
both intended and desirable; others are both unintended and undesirable.
When two drugs interact, three outcomes are possible:
- (1) one drug may intensify the effects of the other
- (2) one drug may reduce the effects of the other
- (3) the combination may produce a new response not seen with either drug alone.
When one drug intensifies the effects of another, the interaction often is called
- Potentiative interactions may be beneficial or detrimental.
Interactions that result in reduced drug effects are often called
- inhibitory interactions can be beneficial or detrimental.
Drugs can interact through four basic mechanisms:
- (1) direct chemical or physical interaction
- (2) pharmacokinetic interaction
- (3) pharmacodynamic interaction
- (4) combined toxicity
Some drugs, because of their physical or chemical properties, can interact directly with
- other drugs.
- Direct physical and chemical interactions usually render both drugs inactive.
Because drugs can interact in solution, two or more drugs should never be combined in the same container unless
it has been established that a direct interaction will not occur.
Drug interactions can affect all four of the basic pharmacokinetic processes; that is, when two drugs are taken together, one may alter the
absorption, distribution, metabolism, or excretion of the other.
Drug absorption may be
enhanced or reduced by drug interactions.
One drug can alter the distribution of another by two principal mechanisms:
- (1) competition for protein binding
- (2) alteration of the extracellular pH
Altered metabolism is
one of the most important—and most complex—mechanisms by which drugs interact.
Drugs that increase the metabolism of other drugs do so by
inducing synthesis of hepatic drug-metabolizing enzymes.
Drugs that decrease the metabolism of other drugs do so by
inhibiting synthesis of hepatic drug-metabolizing enzymes.
Drugs that stimulate the synthesis of cytochrome P450 isoenzymes are referred to as
Although inhibition of drug metabolism can be beneficial, as a rule inhibition has
- undesirable results.
- In most cases, when an inhibitor increases the level of another drug, the outcome is toxicity.
Drugs can alter all three phases of renal excretion:
filtration, reabsorption, and active secretion
Most of the drugs that induce or inhibit P450 have the same impact on
Drugs that induce PGP can have the following impacts on other drugs:
- Reduced absorption—by increasing drug export from cells of the intestinal epithelium into the intestinal lumen
- Reduced fetal drug exposure—by increasing drug export from placental cells into the maternal blood
- Reduced brain drug exposure—by increasing drug export from cells of brain capillaries into the blood
- Increased drug elimination—by increasing drug export from the liver into the bile and from renal tubular cells into the urine
The two basic types of pharmacodynamic interactions are
- (1) interactions in which the interacting drugs act at the same site
- (2) interactions in which the interacting drugs act at separate sites
Pharmacodynamic interactions may be
potentiative or inhibitory.
Interactions that occur at the same receptor are almost always
Inhibition occurs when
- an antagonist drug blocks access of an agonist drug to its receptor.
- Even though two drugs have different mechanisms of action and act at separate sites, if both drugs influence the same physiologic process, one drug can alter responses produced by the other. Interactions resulting from effects produced at different sites may be potentiative or inhibitory.
Drug-drug interactions may increase or decrease the intensity of responses.
Interactions are especially important with drugs that have a
narrow therapeutic range.
The nurse can help reduce the risk of adverse interactions by
minimizing the number of drugs a patient is given and by taking a thorough drug history.
Drug-food interactions are both
important and poorly understood.
Food frequently __________ the rate of drug absorption and occasionally the __________. For some drugs, food may _______.
- extent of absorption
- increase the extent of absorption
_______ can inhibit the metabolism of certain drugs, thereby raising their blood levels.
- Grapefruit juice
- Grapefruit juice exerts this effect by inhibiting CYP3A4, an isoenzyme of cytochrome P450 found in the liver and the intestinal wall.
Drug-food interactions sometimes increase
- drug toxicity.
- The combination of a monoamine oxidase inhibitor with tyramine-rich food is the classic example.
To administer a drug with food means to administer it
with or shortly after a meal.
To administer a drug on an empty stomach means to administer it
either 1 hour before a meal or 2 hours afterward.
When combined with conventional drugs, dietary supplements may cause
- significant drug-supplement interactions.
- The greatest concerns are interactions that reduce beneficial responses to conventional drugs and interactions that increase toxicity.
An adverse drug reaction is any:
- noxious, unintended, and undesired effect that occurs at normal drug doses.
Patients at increased risk of adverse drug events include
the very young, older adults, the very ill, and those taking multiple drugs.
A side effect is formally defined as
a nearly unavoidable secondary drug effect produced at therapeutic doses.
Toxicity is defined as
an ADR caused by excessive dosing.
An allergic reaction is
- an immune response;
- the intensity of allergic reactions is largely independent of dosage.
An idiosyncratic effect is
an uncommon drug response resulting from a genetic predisposition.
An iatrogenic disease is
a drug- or physician-induced disease.
Physical dependence is
a state in which the body has adapted to drug exposure in such a way that an abstinence syndrome results if drug use is discontinued.
Because a variety of drugs can cause physical dependence of one type or another and because withdrawal reactions have the potential for harm, patients should be warned against
abrupt discontinuation of any medication without first consulting a healthcare professional.
The term carcinogenic effect refers to
the ability of certain medications and environmental chemicals to cause cancers.
A teratogenic effect is
a drug-induced birth defect.
Many drugs are toxic to specific organs. Two types of organ-specific toxicity deserve special comment:
- (1) injury to the liver
- (2) altered cardiac function, as evidenced by a prolonged QT interval on the electrocardiogram (ECG).
______ are the leading cause of acute liver failure, a rare condition that can rapidly prove fatal. Combining a hepatotoxic drug with certain other drugs (e.g., alcohol) may increase the risk of liver damage.
The term QT interval drugs, or simply QT drugs, refers to
drugs that can prolong the QT interval on the ECG, thereby creating a risk of serious dysrhythmias.
Because newly released drugs may have as-yet unreported adverse effects, the nurse should be alert for
unusual responses when giving new drugs. If a drug is suspected of causing a previously unknown adverse effect, the nurse should report the effect to MEDWATCH, the U.S. Food and Drug Administration’s (FDA’s) Medical Products Reporting Program.
The responsibility for reducing ADRs lies with
everyone associated with drug production and use.
The pharmaceutical industry must strive to produce ________; the prescriber must select the ________ for a particular patient; the nurse must evaluate patients for _____________; and patients and their families must watch for signs that ________.
- the safest medicines possible
- least harmful medicine
- ADRs and educate patients in ways to avoid or minimize harm
- an ADR may be developing and seek medical attention if one appears
For drugs with especially serious adverse effects, the FDA now requires one or more of the following:
- a Medication Guide for patients,
- a Boxed Warning to alert prescribers, and/or
- a Risk Evaluation and Mitigation Strategy (REMS), which can involve patients, prescribers, and pharmacists.
To help determine if a particular drug is responsible for an adverse effect, the following questions should be considered:
- Did symptoms appear shortly after the drug was first used?
- Did symptoms abate when the drug was discontinued?
- Did symptoms reappear when the drug was reinstituted?
- Is the illness itself sufficient to explain the event?
- Are other drugs in the regimen sufficient to explain the event?
Medication errors are a major cause of
- morbidity and mortality.
- A medication error is any preventable event that may cause or lead to inappropriate medication use or patient harm while the medication is in the control of the healthcare professional, patient, or consumer. Such events may be related to professional practice, healthcare products, procedures, and systems, including prescribing; order communication; product labeling, packaging and nomenclature; compounding; dispensing; distribution; administration; education; monitoring; and use.
Medication errors can be made by
many people, beginning with workers in the pharmaceutical industry, followed by people in the healthcare delivery system, and ending with patients and their family members.
In the hospital setting, a medication order must be
- processed by several people before it reaches the patient.
- All of these people can make a mistake. Fortunately, most are also in a position to catch mistakes made by others.
- The nurse is the patient’s last line of defense against medication errors made by others—and the last person with the opportunity to make an error.
Because the nurse is the last person who can catch mistakes made by others and because no one is there to catch mistakes the nurse might make, the nurse bears a unique responsibility
for ensuring patients’ safety.
The three most common types of fatal medication errors are
- giving an overdose
- giving the wrong drug
- using the wrong route
The three most common causes of fatal medication errors are
- human factors (performance or knowledge deficits and miscalculation of dosage)
- communication mistakes
- confusion caused by similarities in drug names
A central theme in the effort to reduce medication errors is changing the institutional culture from one that focuses on “naming, blaming, and shaming” those who make mistakes to one focused on designing institution-wide processes and systems that can prevent errors from happening. Effective measures for reducing medication errors include
- (1) replacing handwritten medication orders with a computerized order entry system
- (2) having a clinical pharmacist accompany intensive care unit physicians on rounds
- (3) using a computerized bar-code system
- (4) using medication reconciliation when patients undergo a transition in care
The _________ has compiled a list of error-prone abbreviations, symbols, and dose designations, and has recommended against their use. This list includes eight entries that have been banned by ________.
- Institute for Safe Medication Practices
- The Joint Commission
The National Coordinating Council for Medication Error Reporting and Prevention was established to
facilitate the reporting, understanding, and prevention of medication errors.
Nurses can report a medication error via the
- Medication Errors Reporting (MER) Program
- a nationwide system run by the Institute for Safe Medication Practices. All reporting is confidential, and it can be done by phone, by fax, or online.
Drug use among older adults is
Although older adults constitute only 12% of the U.S. population, they consume
31% of the nation’s prescribed drugs
Older patients are _________ to drugs than are younger adults, and they show _________ variation.
- more sensitive
- wider individual
Older patients experience ____ adverse drug reactions and drug-drug interactions.
The principal factors underlying complications of adverse drug reactions and drug-drug interactions are
- (1) altered pharmacokinetics (secondary to organ system degeneration)
- (2) multiple and severe illnesses
- (3) multiple-drug therapy
- (4) poor adherence
Individualization of therapy for older adults is essential:
Each patient must be monitored for desired and adverse responses, and the regimen must be adjusted accordingly.
Age-related decline in organ function alters the
absorption, distribution, metabolism, and excretion of drugs.
The rate of drug absorption may be _____ in older adults, although the percentage of absorption usually is unchanged.
Four major factors can alter drug distribution in older adults:
- (1) an increased percentage of body fat
- (2) a decreased percentage of lean body mass
- (3) a decrease in total body water
- (4) a reduced concentration of serum albumin
Rates of hepatic drug metabolism tend to decline with age; therefore, the half-lives of certain drugs may be
- increased, prolonging responses.
- Renal function, and therefore renal drug excretion, undergoes a progressive decline beginning in early adulthood.
Beta-adrenergic blocking agents (drugs used primarily for cardiac disorders) are ________ in older adults than in younger adults, even when present in the same concentrations.
Possible explanations for this beta-blockers being less effective in older adults include
- (1) a reduction in the number of beta receptors
- (2) a reduction in the affinity of beta receptors for beta-receptor blocking agents
Drug accumulation secondary to reduced renal excretion is the most important cause of
- adverse drug reactions in older adults.
- In these patients, the proper index of renal function is creatinine clearance, not the serum creatinine level.
- Alterations in receptor properties may underlie altered sensitivity to some drugs. However, information on such pharmacodynamic changes is limited.
Adverse drug reactions (ADRs) are _______ common in older adults than in younger adults, accounting for about 16% of hospital admissions among older individuals and 50% of all medication-related deaths.
7 times more
Multiple factors predispose older patients to ADRs. The most important are:
- Drug accumulation secondary to reduced renal function
- Greater severity of illness
- The presence of multiple pathologic conditions
- Greater use of drugs with a low therapeutic index
- Increased individual variation secondary to altered pharmacokinetics
- Inadequate supervision of long-term therapy
- Poor patient adherence
Measures that help reduce ADRs in older adults include:
- Taking a thorough drug history, including over-the-counter medications
- Accounting for the pharmacokinetic and pharmacodynamic changes that occur with aging
- Initiating therapy with low doses
- Monitoring clinical responses and plasma drug levels to provide a rational basis for dosage adjustment
- Using the simplest regimen possible
- Monitoring for drug-drug interactions and iatrogenic illness
- Periodically reviewing the need for continued drug therapy and discontinuing medications as appropriate
- Encouraging the patient to dispose of old medications
- Taking steps to promote adherence
- Avoiding drugs on the Beers list, which identifies drugs with a high likelihood of causing adverse effects in older adults
Between 26% and 59% of older patients fail to take their medicines as prescribed. Multiple factors underlie nonadherence to the prescribed regimen. Among these are:
- -failure to comprehend instructions
- -inability to pay for medications
- -use of complex regimens
- All of these factors can contribute to unintentional nonadherence. Most cases (75%) of nonadherence among older adults are intentional. The principal reason given for intentional nonadherence is the patient’s conviction that the drug was simply not needed in the dosage prescribed. Unpleasant side effects and expense also contribute to intentional nonadherence.
Measures to promote adherence include:
- Simplifying the regimen so that the number of drugs and doses per day are as small as possible
- Explaining the treatment plan using clear, concise verbal and written instructions
- Choosing an appropriate dosage form (e.g., a liquid formulation if the patient has difficulty swallowing)
- Labeling drug containers clearly and avoiding containers that are difficult to open by patients with impaired dexterity
- Suggesting the use of a calendar, diary, or pill counter to record drug administration
- Asking the patient whether he or she has access to a pharmacy and can afford the medication
- Enlisting the aid of a friend, relative, or visiting healthcare professional
- Monitoring for therapeutic responses, adverse reactions, and plasma drug levels