Aging and Drugs
Drugs, the most common medical intervention, are an important part of medical care for older people. Without drugs, many older people would function less well or die at an earlier age.
Older people tend to take more drugs than younger people because they are more likely to have more than one chronic medical disorder, such as high blood pressure, diabetes, or arthritis. Most drugs used by older people for chronic disorders are taken for years. Other drugs may be taken for only a short time to treat such problems as infections, some kinds of pain, and constipation. Among people who are age 65 years or older, 90% take at least 1 drug per week, more than 40% take at least 5 different drugs per week, and 12% take 10 or more drugs per week. Women typically take more drugs than men. Older people who are frail, hospitalized, or in a nursing home take the most drugs. Nursing home residents are prescribed an average of 7 to 8 different drugs to take on a regular basis. Older people also take many nonprescription (over-the-counter, or OTC) drugs. Many OTC drugs are potentially hazardous for older people.
Many of the improvements in the health and function of older people during the past several decades can be attributed to the benefits of drugs.
Vaccines help prevent many infectious diseases (such as influenza and pneumonia) that once killed many older people.
Antibiotics are often effective in treating pneumonia and many other serious infections.
Drugs to control high blood pressure (antihypertensives) help prevent strokes and heart attacks.
Drugs to control blood sugar levels (insulin and other antihyperglycemic drugs) enable millions of people with diabetes to lead normal lives. These drugs also reduce the risk of eye and kidney problems that diabetes can cause.
Drugs to control pain and other symptoms enable millions of people with arthritis to continue to function.
However, drugs can have effects that are not intended or desired (side effects). Starting in late middle age, the risk of side effects related to the use of drugs increases. Older people are more than twice as susceptible to the side effects of drugs as younger people. Side effects are also likely to be more severe, affecting quality of life and resulting in visits to the doctor and in hospitalization.
Older people are more susceptible to the side effects of drugs for several reasons:
As people age, the amount of water in the body decreases, and the amount of fat tissue increases. Thus, in older people, drugs that dissolve in water reach higher concentrations because there is less water to dilute them, and drugs that dissolve in fat accumulate more because there is relatively more fat tissue to store them (see Drug Distribution).
Older people usually take more drugs and have more disorders.
People who take more drugs have a higher risk of drug interactions.
Fewer studies have been done in older people to help identify appropriate doses of drugs.
Older people are more likely to have chronic medical disorders that may be worsened by drugs or that may affect how the drugs work.
Because of these age-related changes, many drugs tend to stay in an older person’s body much longer, prolonging the drug’s effect and increasing the risk of side effects. Therefore, older people often need to take smaller doses of certain drugs or perhaps fewer daily doses. For example, digoxin, a drug sometimes used to treat certain heart disorders, dissolves in water and is eliminated by the kidneys. Because the amount of water in the body decreases and the kidneys function less well as people age, digoxin concentrations in the body may be increased, resulting in a greater risk of side effects (such as nausea or abnormal heart rhythms). To prevent this problem, doctors may use a smaller dose. Or sometimes other drugs can be substituted.
Older people are more sensitive to the effects of many drugs. For example, older people tend to become sleepier and are more likely to become confused when using antianxiety drugs or sleep aids to treat insomnia. Some drugs that lower blood pressure tend to lower blood pressure much more dramatically in older people than in younger people. Larger decreases in blood pressure can lead to side effects such as dizziness, light-headedness, and falls. Older people who have such side effects should discuss them with their doctor.
Some Drugs Particularly Likely to Cause Problems in Older People
Many commonly used drugs have anticholinergic effects. These drugs include some antidepressants (amitriptyline and imipramine), many antihistamines (such as diphenhydramine, contained in OTC sleep aids, cold remedies, and allergy drugs), and many antipsychotics (such as chlorpromazine and clozapine). Older people, particularly those with memory impairment, are particularly susceptible to anticholinergic effects, which include confusion, blurred vision, constipation, dry mouth, and difficulty starting to urinate. Some anticholinergic effects, such as reduction of tremor (as in the treatment of Parkinson disease) and reduction of nausea, are desirable, but most are not.
A drug may have a side effect because it interacts with
A disorder, symptom, or condition other than the one for which the drug is being taken (drug–disease interaction)
Another drug (drug–drug interaction)
Food (drug–food interaction)
A medicinal herb (drug–medicinal herb interaction—see Table: Some Possible Medicinal Herb–Drug Interactions)
Because older people tend to have more diseases and take more drugs than younger people, they are more likely to have drug–disease and drug–drug interactions. In many drug-disease interactions, taking a dug can worsen a disorder, symptom, or condition (see Table: Some Disorders and Symptoms That Can Be Worsened by Drugs in Older People).
Some Disorders and Symptoms That Can Be Worsened by Drugs in Older People
Patients, doctors, and pharmacists can take steps to reduce the risk of drug–disease and drug–drug interactions. Because OTC drugs and medicinal herbs can interact with other drugs, people should ask their doctor or pharmacist about combining the use of these drugs with prescription drugs.
Not following a doctor’s directions for taking a drug (called noncompliance or nonadherence) can be risky (see Adherence to Drug Treatment). Older age alone does not make people less likely to take drugs as directed. However, up to half of older people do not take drugs as directed. Not taking a drug, taking too little, or taking too much can cause problems. Taking less of a drug because it has side effects may seem reasonable, but people should talk to a doctor before they make any changes in the way they take a drug.
To benefit from taking drugs, people must remember not only to take their drugs but also to take them at the right time and in the right way. When several drugs are taken, the schedule for taking them can be complex. For example, drugs may have to be taken at different times throughout the day to avoid interactions. Some drugs may have to be taken with food. Other drugs have to be taken when no food is in the stomach. The more complex the schedule, the more likely people are to make mistakes following it. For example, bisphosphonates (such as alendronate and risedronate), which are used to increase bone density, need to be taken on an empty stomach and with only water (at least a full glass). If these drugs are taken with other liquids or food, they are not absorbed well and do not work effectively.
If older people have memory problems, following a complex schedule is even harder. Such people usually need help, often from family members. The doctor can be asked about simplifying the schedule. Often, doses can be rescheduled to make taking the drugs more convenient or reduce the total number of daily doses. Also, over time, some drugs may not be needed any longer and can be stopped.
The following things can help people remember to take their drugs as prescribed:
A pharmacist can provide containers that help people take drugs as instructed. Daily doses for 1 week or 2 weeks may be packaged in a plastic pack marked with the days or with the times of the day, so that people can keep track of doses taken by noting the empty spaces. Some pharmacies can package drugs in blister packs, so that the daily dose can be easily removed and kept track of. However, such packaging may cost a little more.
More elaborate containers with a computerized reminder system are available. These containers beep, flash, or talk at dosing time.