Geriatric Pharmacology & Pharmacotherapy

Instructor: Artem Cheprasov

Artem has a doctor of veterinary medicine degree.

Have you ever wondered what changes occur in our body as we age, and how those changes translate to the use of medications? This lesson goes over a wide variety of such changes and their effects.

Geriatric Changes

What happens as you age after young adulthood? Well, let's face it, you slow down and things don't work nearly as well as they used to. For example, older people aren't as fast as young people, all else equal of course, and their heart may not work as efficiently. The same goes for most other organ systems of the body. Things change and not always for the better.

This is why it's important to understand the very core systemic (body-wide) changes that occur in the geriatric population, which includes older adults. This lesson will point out many of these key changes and how they tie in with pharmacology and pharmacotherapy.

Organ System Changes

First, let's start by looking at some organ systems, how they change with age, and what that means therapeutically with respect to drugs.

The gastrointestinal system is affected by age in more than one way. As a person ages, their gastric (stomach) pH increases. This means their gastric secretions become more alkaline. Their gastrointestinal motility, or how easily material moves through, decreases as well. All of this translates into an increased absorption time for a drug that is taken orally.

Once the drugs are absorbed by the gastrointestinal system, they are delivered to the liver. As people get older, the liver enzymes responsible for metabolizing (biochemically altering) the drugs are no longer as fast nor as efficient at their job. This means drugs take longer to be metabolized by the liver, and they are metabolized less completely at the same time.

Once the drugs are metabolized by the liver, they need to be delivered to target tissues via the circulatory system, which includes the heart and blood vessels. However, as a person ages, their cardiac output decreases. Their circulation becomes impaired not only as a result of decreased cardiac output, but because of age-accumulated damage to the blood vessels and other hormonal factors. What does this mean pharmacologically? Well, the circulatory system is the highway that delivers the drugs a person may take. If this system has slowed down, then the drugs will be delivered to the tissues with a delay compared to a young person.

Finally, the drugs that are in the body must eventually be excreted out of the body. The kidneys are the main exit point for many drugs. But the problem is that as a person enters their twilight years, the rate at which the kidneys filter out the drugs decreases and the number of functional filters also decreases. That double whammy means that drugs are excreted more slowly and less efficiently.

Other Changes of Note

Another factor that needs to be considered is the person's body composition. This may include their total body water and body fat. For example, older adults tend to have more body fat compared to younger adults. This means that greater amounts of a lipid-soluble (fat-soluble) drug will be absorbed by the fat. What may this mean clinically? Well, if more of it is absorbed by the fat, less of it is available to enact a desired effect.

Desired effects are produced by interaction of the drug with a drug receptor. But with age, the number of drug receptors could change, the affinity of the receptors to the drugs may be altered, and consequently, a senior adult may be more or less sensitive to a drug based on these changes. In practice, the dose of the drug is usually lowered for safety's sake.

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