Medications Work Differently in Older Adults

Medication dosages, as well as information about the effectiveness and side effects of medication, are generally determined by studies done in relatively young, healthy people. This information may not be appropriate for older adults, because changes can occur with age that can affect how our bodies deal with drugs. 

Changes in metabolism and body composition as we age can affect how well a medication works. Both the effectiveness and side effects of medications can be affected by diseases and conditions that develop later in life, and the medicines we take for them.

Changes in the Body

To work effectively, medications must be:

  • Absorbed into the body (usually through the stomach and intestines)
  • Distributed to where they are needed
  • Metabolized (chemically changed to become effective or to be eliminated from the body)
  • Eliminated from the body (usually through the urine)

Age-related changes in the body can affect the appropriate dosage, depending on the person. 

Changes that decrease a medication’s metabolism and elimination may mean that you’ll need a lower dose or that some medications that are useful for younger adults can have more harms than benefits for older adults. 

When taking medications, the following factors will make sure you have the best outcome:

  • When the correct medication is prescribed for the correct condition
  • When the medication is right for you and your condition
  • When you take the proper dose for the length of time your healthcare provider recommends

Unfortunately, these guidelines are not always black and white. Many factors influence medication treatment. For example, a person may be on medicines for other conditions, in addition to the new one just prescribed. 

Multiple Medical Conditions

Older adults often have multiple medical conditions. These may affect how medications are absorbed, metabolized, or eliminated. Medications used to treat one condition may also make another chronic problem worse. For example, older adults with memory problems may experience worse memory, behavior problems, or sleep disturbance caused by medicines used to treat their other medical problems.

Effects of Food and Beverages on Medications

Medications may be affected by food, beverages, and other medications that you take at the same time. For example, some antibiotics are not absorbed well when taken with foods, beverages, or other medications that contain a lot of calcium, magnesium, or iron (such as antacids, vitamins, or dairy products). Certain foods, such as grapefruit juice, can also change the metabolism of certain medications. This may cause the medicine to build up in the body.

Medication Interactions

An older person may be on medicines for other conditions, in addition to the new one just prescribed. This could result in the new medication not working the way it should, or there may be an interaction between the medications. Some medications can slow down the metabolism of other medications. Others can speed up the process. 

Other Factors

Other factors may affect how the body deals with medications. For example, a medication's effect can be affected by cigarette smoking, drinking caffeinated or alcoholic beverages, changes in diet, and viral infections.

Common side effects of medicines in older adults can be falls, weight loss or weight gain, and cognitive changes.  These, in turn, can contribute to a person having increased frailty, with weakness, less endurance, and less ability to function well in day-to-day life.


Many older adults cope with more than one medical condition at the same time. Often, managing these medical conditions can mean that the older adult may need many different medications.

When older adults take five or more medicines, it is called “polypharmacy.” With polypharmacy, the medicines can interact with each other and with your body in harmful ways.  For example, the medications can increase negative side effects or decrease desired effects.

Primary care providers know about the negative effects that taking multiple medications can cause. But unless you tell them about all the medicines you’re taking, they may not realize what’s causing your problem.

Tell all your healthcare providers about all of the medicines you are taking, no matter which provider prescribed them to you.

Discuss vitamins, supplements, and other over the counter medications, as well as any prescribed by other healthcare providers. Then you and your provider can figure out whether one or more drugs might be changed or stopped.

Also, if you have experienced an unwanted symptom (such as having had a fall or having memory problems), be sure to tell your healthcare provider - and ask if this could be caused by one of your medicines.

Prescribing Cascade

Sometimes, one of the medications you’re taking may cause new symptoms, or make symptoms you already have get worse. This could potentially lead to what is called a “prescribing cascade.” This is when a side effect of a medication is mistaken for a new medical condition, so your healthcare provider uses a new medicine to treat the side effect of the other medication. This can lead to being prescribed even more medications and having even more side effects. Therefore, ask your healthcare provider to review all of your medicines with you. And before you get a new medicine, ask if one of the medicines you are already taking might be causing the problem the new medicine is meant to treat.


Last Updated January 2019