Question

Case Study, Chapter 11, Health Care of the Older Adult

2. The nurse is completing the admission assessment for a patient scheduled for cataract surgery in the outpatient center. Because the patient is over the age of 70 and has several chronic conditions, including hypertension and congestive heart failure, the nurse focuses on completing a thorough medication history. (Learning Objective 4)

What questions should the nurse include in the medication history?

The patient states that she stopped taking one of her medications due to cost, since her health insurance would not reimburse for the medication. What are other reasons that older adults may be noncompliant with ordered medications?

How does aging affect drug absorption, metabolism, distribution, and excretion?

Answer 1

What are other reasons that older adults may be noncompliant with ordered medications?

Behavioral factors: (social isolation, social and health beliefs, and economic condition) Many elderly people live alone. Studies have shown that people who live alone more often fail to comply with medication regimens. For those elderly on fixed, minimal incomes, the ability to purchase expensive medications may also be a factor in noncompliance.

Physiological factors: Loss of vision or hearing can impede an elderly person's ability to read important information about his prescription or to hear instructions about his regimen. Mobility limits, type of disease, the presence of symptoms, memory loss, depression, and cognitive impairment are other physiological variables that can negatively affect compliance.

Health Care Provide and Patient Interaction factors: (communication between the physician, the pharmacist, and the patient) The quality and content of a physician's instructions, the content of a pharmacist's label, and the ability of a patient to ask questions can all affect compliance.

Treatment factors: (duration and complexity of the medication regimen) Compliance rates decrease when the treatment is long term and when the regimen includes many different medications that must be taken concurrently. Other treatment factors include the type of medication prescribed, and the patient's perception of the medication.

Health Education is the key to improving compliance.
Strategies to improve compliance include physicians and pharmacists better educating patients about their medication regimens. Effective counseling by the physician and pharmacist may be the single best intervention for patients with compliance problems. Public education groups are also currently involved in informing and educating elderly citizens about medication issues. Compliance aids such as medication reminder charts may be useful tools for patients with memory impairments, or patients on complex medication regimens.

How does aging affect drug absorption, metabolism, distribution, and excretion?

As age increases, the functions of organs and tissues in the body decline gradually. In general drug absorption, distribution in the body, activity, metabolism and excretion can all change as a result of ageing. Due to this decline in organ function, drug absorption, distribution, metabolism and excretion in elderly people are worse than those of young people. In addition it is common for multiple medical conditions to be present in older patients which can lead to a greater potential for medication problems due to polypharmacy. Furthermore, drug sensitivity is different in the elderly, who are prone to have adverse reactions to drugs. Thus, it is very important to design drugs according to the characteristics of the elderly.

Drug absorption

Drug dissolution is effected by the aging of the gastrointestinal mucosa in the elderly and the decrease of gastric acid secretion (25% - 20% reduction). Tablets or capsules are designed to allow the full release of the drug over a specific time schedule. If the stomach is full or empty, this may affect the speed at which absorption occurs. However, due to the weakening of gastrointestinal movement in the elderly and slow gastric emptying rate, drugs stay longer in the gastrointestinal tract, which is conducive to greater drug absorption. Drug absorption is theoretically reduced in the older patient due to loss of mucosal intestinal surface, decrease in gastrointestinal blood flow and reduced gastric acidity. The combination of these negative and positive factors usually results in normal drug absorption rate.

Drug distribution

Once a drug is absorbed it is carried around the body in the blood stream. Distribution is the term used to describe the movement of the drug into body tissues. The extent and pattern of distribution will be dependent mainly on the plasma and tissue protein binding characteristics of the drug and its lipid solubility (solubility in fatty tissues). Due to a decrease in the amount of plasma proteins, an increase of fat percentage and decrease of lean tissues (skeletal muscle, liver, brain, kidney, etc.), when the same dose of drug is used in elderly and young people, it has a high level of free state and greater functionality in the elderly. Drug distribution is affected by the changes in body composition associated with age. The elderly are therefore more prone to toxic reactions. Active uptake into tissues may also be influenced by ageing. There is also evidence that the blood-brain barrier is less intact in older patients thus allowing certain drugs to distribute into the brain in increased concentration.

Drug metabolism

The reduction in total liver size would be expected to result in a decrease in the levels of drug metabolising enzymes. A further decrease in efficiency would be expected to result from the reduction in liver blood flow as this would result in a decrease of exposure of the drug to metabolising enzymes. There are no abnormal changes in liver function indexes in the elderly, but the activity of drug metabolism enzyme in the liver is decreased so that the half-life of the drug is prolonged. Also, the age associated reduction of parenchymal cells in the liver and a reduction of liver blood flow affects the ability of the liver to metabolise drugs. These factors further compound the drug scavenging capacity of the elderly, causing drug effect enhancement and more adverse reactions. Certain drugs cause induction of liver enzymes resulting in faster metabolism of some other drugs whilst other drugs called enzyme inhibitors reduce the action of the liver enzymes resulting in slow metabolism of other drugs. This effect is of particular importance when one of these enzyme affecting drugs is started, stopped or the dose changed, and is especially important in older patients who many be on several medications at any one time.

Drug excretion

The kidneys remove substances from the blood and eliminate them in the urine. The total size of the kidneys decrease with age, as does the number of functioning nephrons. There is also decreased renal blood flow with increasing age. The kidney is the main organ involved in drug excretion; therefore the pharmacokinetics of aging induced change mainly results from reduced kidney functionality. It is the most important factor in producing toxic drug reactions in the elderly. This will result in a progressive decrease in renal function as demonstrated by measures of the glomerular filtration rate (GFR). By the age of 70, both renal blood flow and the GFR will have decreased on average by about 35% from the age of 20.

In older people, renal clearance is frequently aggravated by the effects of enlarged prostate or chronic urinary tract infection. Acute illness may lead to rapid reduction in renal clearance, especially if accompanied by dehydration. Hence a patient stabilised on a drug with a narrow therapeutic index (the difference between effective and toxic dose being small) may rapidly develop adverse effects in the event of an acute illness.