Medication Usage

Miss Shurouq Qadose

4/4/2011

Pharmacokinetic; is the study of the movement of drug molecules in the body in relation to drug’s absorption, distribution, metabolism and excretion.

Pharmacodynamics; is the process by which a drug changes the body (e.g., alters cell physiology).

Medication usage among older adults is complicated by several issues. Normal changes of aging often influence the manner in which medications are utilized by older adults. These changes affect how medications are absorbed through the gastrointestinal tract, skin, or musculature; distributed via the circulatory system; metabolized by the liver; and

cleared from the body through the kidneys.

Pharmacokinetic

These four pharmacokinetic mechanisms are also influenced by acute and chronic illnesses common in older adulthood, which may further slow or impair the ability of organ systems to absorb, distribute, metabolize, and excrete medications.

Pharmacokinetic Changes With Aging

For example, knowing that older adults

experience slower absorption of medications may result in the need for a greater time period to achieve desired drug effect. It is important for nurses caring for older adults to understand the impact of normal and pathological age-related changes of aging in order to provide the plan of care that will achieve optimal medication effectiveness.

Pharmacodynamics

Pharmacodynamic changes among older adults are challenging for researchers, partly because specific organ responsiveness to medications changes as people age.

For example, the California Drug Registry (2005) reports that increased receptor responses have been documented for benzodiazepines (commonly used for sleep enhancement), opiates (used for pain relief), and

warfarin (used for several conditions in which blot clots would commonly form).

Changes in pharmacodynamics are of concern to nurses caring for older adults because they may result in both the increased effects of medication among older adults and a higher incidence of adverse drug reactions.

Medication Absorption

Several changes occur in the gastrointestinal system throughout life. These include an increase in gastric pH and a change in the amount of fluid within the stomach, as well as a decrease in the time required to empty stomach contents and move active products and nutrients across membranes.

As part of the normal changes to the elderly circulatory system, there is a decrease in the intestinal blood flow and altered intestinal motility.

The slowing of many gastrointestinal symptoms leads health care professionals to believe that an increased amount of time is necessary for medications to become effective in older adults. It is important to note that increased time for absorption may also increase the amount of medication absorbed. For example, vitamins A and C may be more readily absorbed among older adults because they remain in the small intestine longer.

It is important to consider the number of changes in nutritional levels and eating habits as well as various disease states that may affect drug absorption. There is a substantial prevalence of nutritional deficiencies among older adults, partly due to normal changes of aging.

For example, decrease in smell, vision, and taste and the high frequency of dental problems makes it difficult for the older adult to maintain adequate daily nutrition.

Nutrition and hydration assessment are necessary

to help older adults minimize the effects of aging on drug absorption. Teachings regarding appropriate food choices, such as avoiding spicy foods, which may be irritating to the stomach lining, are essential

to changing nutritional patterns and reducing the effects of nutrition on drug absorption.

Several diseases occur more commonly in the older population and impact drug absorption. Achlorhydria

(Achlorhydria and hypochlorhydria refer to states where the production of gastric acid in the stomach is absent or low).

a disease that greatly reduces the acidity of the stomach, may make it difficult to dissolve medications for absorption.

Other gastrointestinal disorders, such as gastroesophageal reflux disease, or surgery to the stomach or small intestine, may also alter drug absorption. Moreover, polypharmacy among the elderly plays an impact on drug absorption, as multiple medications compete for the same sites. For example, antacids, taken with some antibiotics or cardiac medications may decrease the absorption of the later.

75-year-old man in good health and residing in the

community. He walks 2 miles each day, continues to work, and takes a daily multivitamin. He visits the primary care clinic for a routine physical examination and complains of fatigue, headaches, flushing, and difficulty sleeping. His history, health assessment, and physical exam do not reveal any acute or chronic medical problems.

Medication Distribution There are several factors that affect drug distribution

among older adults. These include changes in fl uid pH, plasma protein, and serum albumin concentrations; reduced lean body mass; a relative decrease in total body water; and an increase in the percentage of body fat, blood flow, and tissue–

protein concentration. These normal aging changes have the potential to alter the distribution of the medication compared to the blood concentration.

Total body intracellular and extracellular water decreases by as much as 15% among older adults. This reduces the distribution of water- soluble

medications and increases the distribution of fat-soluble medications. For example, medications such as digoxin, lithium, aminoglycosides, which are water soluble, have the tendency to become elevated

among older adults.

Lean body mass is reduced in older adults. The proportion of fat tissue increases with age from 18% to 36% in men and from 36% to 48% in women between the ages of 20 and 80 years. Consequently, fat-soluble medications, such as barbiturates, phenothiazines, benzodiazepines, and phenytoin, have the tendency to accumulate in the increased fat distribution of older adults resulting in a prolonged half-life of these medications.

Alterations in plasma protein binding, which may occur as part of the normal aging process, are of particular concern to nurses caring for older adults (Hogstel, 2001). This change could potentially alter the distribution of a medication significantly, as well as change the half-life of a medication and disrupt the steady flow of medication needed for disease management.

When serum albumin is decreased, the number of available binding sites for medications is also decreased. This results in an increased amount of active medication in the circulation and the potential

for drug toxicity as free medication is potentially absorbed.

The cardiac output, which decreases by about 1% each year after the age of 30, has further potential to alter medication distribution. Moreover, blood flow to the liver, which decreases from 0.3% to 1.5% per year,

and blood flow to the kidneys must also be considered as metabolism and elimination of such medications is dependent on their distribution to these organs

Hepatic Metabolism

Normal changes of aging that affect the biotransformation of medications vary greatly among older adults. Unlike medication absorption and distribution, determining the function of the liver is difficult.

Normal aging liver changes that affect medication metabolism include reduced blood flow to the liver and a decrease in functional liver cells, which have the potential to impact how effectively medications are transformed. There are two phases of metabolism within the liver that affect medication processes: phase I metabolism, which involves the use of enzymes to break down medications, is reduced among older adults; phase II metabolism, known as conjugation, is generally not affected by the aging process

Use of multiple medications, alcohol, caffeine, smoking, poor nutrition, and multiple disease processes have the potential to greatly affect liver function and reduce the metabolism of medications.

Renal Elimination

Older adults experience a normal reduction in the number and size of the nephrons, reduced glomerular filtration rate, and decreased renal tubular secretion. Thus, it is generally understood that older adults

will eliminate medications more slowly than younger individuals, resulting in an increased medication half-life.

Medication Interactions

Changes of aging and pharmacodynamics, as well as the presence of disease and the numerous prescription and OTC drugs taken by older adults (polypharmacy), makes this population at high risk for developing

adverse reactions to drugs.

In fact, older adults are estimated to be at 2–3 times higher risk for adverse reactions to medications than their younger counterparts. These adverse reactions result from drug-to-drug interactions, drug and disease interactions, and drug–nutrient interactions.

As the number of medications taken by older adults increases, there is a logical increase in the incidence of interactions between medications. Medication interactions occur when two or more medications are combined together, altering the strength and effectiveness of the medications. Many medication interactions may be predicted when administered to

older adults based on previous knowledge of the drug.

For example, the administration of vitamin K with warfarin is a well-known drug–drug interaction. In this case, the vitamin K increases the effect of warfarin, causing a potentially fatal reduction in clotting ability.

Falman,Lynn, Finch, Doberman, and Gabel (2007) recently reported that the prescribing of inappropriate medications among older adults was common practice. In their study of 4,602 Medicare beneficiary patients over the age of 65, 44% were prescribed a medication that was known to be inappropriate among the elderly.

Medication–Disease Interactions

It is very common that the medications used to treat one disease potentially could affect management of another disease. This is especially true for patients

with hypertension, congestive heart failure, diabetes, and renal failure. In patients with these diseases, the medication take for one can potentially impact the medication taken for another.

For example, the use of several beta-blocker medications among older adults have reportedly contributed to increased episodes of already-existing impotence among older men. Another example may be the use of antihistamines, commonly prescribed

or available over the counter for cold and allergy symptoms. In patients with benign prostatic hypertrophy (BPH), the medications may result in

urinary retention.

Medication–Nutrient Interactions

Medications often interact with nutrients among older adults and have the potential to impact the nutritional status of the population in two specific ways. First, many medications have the tendency to impact appetite. For example, paroxetine, which is commonly prescribed for depression among older adults, may result in a decreased appetite and lead to weight loss and malnutrition.

Conversely, several antipsychotic medications prescribed for bipolar disease or schizophrenia in the elderly may increase appetite resulting in the consumption of food poor in nutrients and obesity

The second major interaction between medications and nutrients surrounds the impact of nutrients on the absorption, distribution, metabolism, and elimination of nutrients. Older adults are at higher risk for medication–nutrient interactions because of normal and pathological aging changes, as well as higher rates of alcoholism and the use of restricted diets to treat disease. For example, the absorption medication may be affected by the intake of the medication with orange juice or milk.

The use of nutritional supplements among the elderly, which contain many nutrients, may also potentially impact medication effectiveness. Administering medications via tube feedings results in a similar risk of nutrient–medication interactions (Hogstel, 2001).

Moreover, certain nutrients may be excreted more quickly if they interact with medications, for example, diuretics, such as thiazide.

To reduce the risk of medication–nutrient interactions, it is important to pay close attention to the known interactions of medications. Medications should be administered with water, as opposed to orange juice, milk, or with nutritional supplements.

Inappropriate Medications

There are a number of medications that have been determined to be inappropriate for older adults and should be used with extreme caution.

These are listed in Table 7.2. Page 186

Consideration of normal aging changes in the amount of subcutaneous, fat, and muscle tissue should be considered when administering parenteral medications to older adults. With the decreasing muscle mass, it is possible that medications designed to reach the muscle may be injected deeper. This may result in damage to underlying tissues, as well as an alteration in expected response time to the medication.

Assessment of a client’s body composition and choice of needle size will help minimize harmful effects of parenteral medication administration to older adults. In addition, changes in vasculature may result in

difficulty accessing peripheral intravenous sites for medication therapy.

It is generally reported that about one-half of all patients take the medications exactly as prescribed upon leaving the physician’s office. The other half take the medications incorrectly, or not at all. Of those who take the medications incorrectly, one-third don’t take it at all, one-third take some, and one-third do not even fill the prescription.

Medication Adherenceباخذالدواء التمسك

Among the reasons for nonadherence to medication regimes is that health care providers fail to give clear instructions on use of the medication and when to take each dose. Multiple prescriptions and complicated administration schedules, for example, medications that change dosages, contribute to lack of adherence (Hogstel, 2001). For example, many patients who wear daily nitroglycerin

patches are not aware that one patch should be removed and the area cleaned, before applying the next patch.

Noncompliance rises along with the chronic illnesses commonly seen among older adults. As the older adult is asked to commit more time and resources to maintaining health, they are less likely to adhere closely to the recommended regimen. It is also important to note that older adults from various cultural backgrounds may not adhere to medication and treatment regimes because such plans conflict with their cultural healing beliefs.

For example, a patient may be prescribed an oral medication to reduce blood pressure, but she may not take the medication, because her cultural background leads her to believe that oral medications are

destroyed in the stomach and, thus, not effective.

In order to promote maximum adherence, it is essential that nurses provide teaching regarding the recommended treatment regimen and assess patients’ understanding, willingness, and capability to comply.

To aid in this teaching, many pharmacies provide information sheets with all new prescriptions that include:

• Name(s) of the medicine

• Ordered dose

• Directions for use

• Possible side effects

• Other drugs that should not be taken concurrently

• What to do if adverse effects occur

Healthy People 2010 defines health literacy as more than just an ability to read; it is action-oriented, leading to an improved capacity to be a full participant in one’s health care. Health literacy requires that older adults not only be able to read information, but understand what they are reading, hear instructions, calculate medications, and communicate questions.

Low health literacy often impacts the ability of older adults to fully understand medication instructions and health interventions. It disrupts clients’ ability

to effective prepare for diagnostic tests, make follow-up appointments, and maintain health. Moreover, low health literacy is a significant factor in noncompliance with health care treatments and medications.

Easily opened containers are preferred by older adults and may be another intervention to increase adherence among older adults. Bold labeling of medications is helpful for visually impaired clients, and a review of medications should be conducted during each visit to a health care provider to encourage medication compliance. Clients should be

encouraged to bring the actual medication container, as opposed to a listing. In this way, generic medications can be assessed, and the amount

of medication remaining in the bottle can be measured against the prescription filled date.

Nurses should always know which medications their clients are taking, what these medications are prescribed for, and what the expected side effects and outcomes are. Changes in medication dosage

and prescribing should be made when medications are found to result in adverse reactions, side effects, or are ineffective in meeting outcomes.

Over-the-counter And Illegally ObtainedNarcotics And Herbal Medications

Older adults use OTC medications and illegal drugs to

treat pain, depression, gastric disturbances, anxiety, memory loss, and other disorders when they are unable to obtain or pay for effective treatment

by health care providers. Typical OTC medications used by older adults include analgesics ( aspirin,

Tylenol, Motrin), sleep aides (Tylenol PM, Benadryl), H2 agonists ( Pepcid), laxatives, and antihistamines. Each of these medications has the potential to cause adverse reactions in the older adult population.

A variety of medications is often used by older adults to reduce pain, enhance mood, or provide sedation. Illegal and narcotic drug use among older adults results in great risk of harm to physical, psychological, and social functioning, and the effects may become long-term.

Nurses may fail to detect narcotic drug use because the symptoms of drug use, including alteration in mental status and function, mimic the symptoms of delirium, depression, and dementia, which occur frequently among older adults. Commonly used medications in these categories include morphine, codeine, Demerol, and marijuana, as well as other commonly used street drugs.

Possible adverse reactions to OTC medications and illegally obtained narcotics include oversedation and respiratory arrest, falls, delirium, metabolic disturbances, and death.

California study also found that complementary and alternative medicine (CAM) was used by 38–50% of ethnic minority elders (Astin, Pelletier, Marie, & Haskell, 2000). Herbal medications may be preferred

over traditional medications among many cultural groups including Chinese and other Asian cultures.

Herbal supplements commonly used by older adults include vitamins C, D, and E, which have shown some evidence of reducing symptoms of osteoarthritis. Ginger and glucosamine have also been used extensively by older adults to reduce arthritis-related pain. Ginkgo biloba is widely used by older adults to enhance memory, and Saw Palmetto ( ( المنشارى is used by many older men البلميطto reduce symptoms of enlarged prostate glands and to prevent prostate cancer. Ginseng في ويسمى الجينسنغ

إنسام نبات ,is used by older adults to reduce stress كورياand St. John’s wort يحيى سيدي بالد نبتة في وتعرف

باسم العرن الشام المراجع عشبة بعض تسميها كما أوالقلب عشبة باسم is often used as an alternative or الحديثة

adjunct treatment for depression.

Ginkgo biloba

المنشارى البلميط

Saw PalmettoGinseng

St. John’s wort

These medications may mask the diagnosis and progression of disease among older adults. For example, Saw Palmetto artificially reduces prostate specific antigen (PSA), the tumor marker for prostate cancer—leading to false negative results for diagnosis

or progression of prostate cancer. Moreover, herbal medications have a high tendency to interact with other medications and conditions. For example, ginger interacts with warfarin, a commonly used blood thinner used by many older adults.

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