Pharmacologic Aspects of Aging

PHARMACOLOGIC ASPECTS OF AGING

Older people use more medications than does any other age group: although they comprise only 12.6% of the total popula-tion, they use 30% of all prescribed medications and 40% of all over-the-counter medications. Medications have improved the health and well-being of older people by alleviating symptoms of discomfort, treating chronic illnesses, and curing infectious pro-cesses. Problems commonly occur, however, because of medication interactions, multiple medication effects, multiple medication use (polypharmacy), and noncompliance. Combinations of pre-scription medications and some over-the-counter medications further complicate the problem.

Any medication is capable of altering nutritional status, which, in the elderly, may already be compromised by a marginal diet or by chronic disease and its treatment. Medications can depress the appetite, cause nausea and vomiting, irritate the stomach, cause constipation or diarrhea, and decrease absorption of nutrients. In addition, they can alter electrolyte balance and carbohydrate and fat metabolism. A few examples of medications capable of alter-ing the nutritional status are antacids, which produce thiamine deficiency; cathartics, which diminish absorption; antibiotics and phenytoin, which reduce utilization of folic acid; and phenothi-azines, estrogens, and corticosteroids, which increase food intake and cause weight gain.

Altered Pharmacokinetics

Pharmacokinetics is the study of the actions of medications in the body, including the processes of absorption, distribution, metab-olism, and excretion. Variability in these processes in older peo-ple (Table 12-3) is caused, in part, by a reduced capacity of the liver and kidneys to metabolize and excrete the medications and by lowered efficiency of the circulatory and nervous systems in coping with the effect of certain medications. Many medications and their metabolites are excreted by the kidney. With advanced age, body weight, total body water, lean body mass, and plasma albumin (protein) all decrease, while body fat increases. Conse-quently, agents that are highly protein-bound have fewer binding sites and higher pharmacologic activity, whereas fat-soluble agents have more binding sites, and therefore enhanced storage and de-layed elimination.

Nursing Implications

The nurse administering medications to older people must be aware of the following:

•          Medications removed from the body primarily by renal ex-cretion remain in the body for a longer time in people withdecreased renal function. Often dosages must be reduced, because overdosage and medication toxicity at usual thera-peutic dosages are common.

•          Medications with a narrow safety margin (eg, digitalis gly-cosides) must be administered cautiously.

•          A decline in cardiac output may decrease the delivery rate to the target organ or storage tissue.

•          The circulatory and central nervous systems of older people are less able to cope with the effects of certain medications, even when blood levels are normal.

•          Idiosyncratic or unusual responses to medications may manifest as toxic reactions and complications.

•          As a result of a slowing metabolism, medication levels may increase in the tissues and plasma, leading to prolonged medication action.

•          Many elderly people have multiple medical problems that require treatment with one or more medications. The pos-sibility of interactions between medications is further magnified if the older person is also taking one or more over-the-counter medications.

•          A high-fiber diet and the use of psyllium (Metamucil) or other laxatives may accelerate gastrointestinal transport and reduce absorption of medications taken concurrently.

•          If, for any reason, a patient is not dependable about taking medication, the nurse must be sure that the pill or capsule is actually swallowed and not retained between the cheeks and the gums or teeth.

Teaching self-administration of medication requires asking the patient questions and requesting return demonstrations to en-sure that learning has occurred. Sensory and memory losses, as well as decreased manual dexterity, can affect the patient’s ability to carry out instructions properly, and the teaching plan will need to be adjusted to meet each patient’s needs. The following steps taken by the nurse can help the patient to manage his or her med-ications and improve compliance:

·       Explain the action, side effects, and dosage of each medication.

·       Write out the medication schedule.

·      Encourage the use of standard containers without safety lids (if there are no children in the household).

·      Suggest the use of a multiple-day, multiple-dose medication dispenser to help patients adhere to the medication sched-ule (Fig. 12-5).

·      Destroy old, unused medications.

·       Review the medication schedule periodically.

·      Discourage the use of over-the-counter medications and herbal agents without consulting a health professional.

·      Encourage the patient to take all medications, including over-the-counter medications, with him or her regularly when visiting the primary health care provider.