Video summary
The primary reason older adults respond differently to medications lies not in their chronological age but in their cellular age, which is influenced by factors such as chronic stress, substance misuse, and overall health conditions. As individuals age, their bodies undergo significant physiological changes, including a loss of muscle mass and an increase in body fat, which directly alter how drugs are distributed and cleared. These biological shifts mean that a person's body might function physiologically like someone much older than their actual birth year, leading to unexpected reactions to standard dosages. Consequently, understanding these underlying mechanisms is crucial for preventing adverse effects and ensuring safe medication management across all age groups.
A critical factor in drug metabolism is the change in body composition, where increased fat mass causes fat-soluble medications to remain in the body longer and accumulate to higher concentrations. Common examples of such drugs include benzodiazepines used for anxiety, opioids for pain relief, statins for cholesterol management, beta-blockers for hypertension, and various antipsychotics. For instance, the half-life of diazepam increases by approximately one hour for every year of age, meaning a seventy-year-old may take up to 70 hours to clear half of the drug from their system compared to just 20 hours for a twenty-year-old. This prolonged retention allows these substances to build up rapidly, significantly increasing the risk of toxicity if the same dosage is prescribed without adjustment.
Conversely, water-soluble drugs like antibiotics, ACE inhibitors, diuretics, and certain pain relievers such as Tylenol face different challenges due to the natural decrease in total body water as people age. With less water available to distribute these substances, they become more concentrated within the body's fluids, similar to how adding a fixed amount of sugar to a smaller volume of water creates a stronger solution. This concentration effect can lead to higher drug levels and potential side effects even when standard doses are administered. Therefore, healthcare providers must be acutely aware that both fat-soluble and water-soluble medications require careful consideration regarding dosage and frequency as the body's composition shifts over time.
Ultimately, the efficiency of the kidneys and liver in clearing these drugs diminishes with age, further complicating medication management. In healthy adults who abstain from harmful substances, kidney clearance decreases by about 1% per year after age forty, while liver clearance drops by approximately 8% annually. However, this natural decline can be accelerated significantly by unhealthy lifestyle choices, substance abuse, or existing conditions like fatty liver disease. Recognizing that chronic stress and other health issues can make an individual's body behave as if they are much older is essential for tailoring treatment plans. By accounting for these physiological realities, medical professionals can better predict drug responses, adjust dosages appropriately, and mitigate the risks associated with polypharmacy in aging populations.
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So, let's start out by talking about why
older adults respond differently to
medications.
And we're going to talk about a lot of
things today, but I want to start out by
pointing out that what we're talking
about is the a-cellular age of the body,
not necessarily the chronological age.
Body composition changes, nutrient
deficiencies, drug interactions, white
matter integrity in the brain,
concurrent health conditions, and kidney
and liver issues are relevant to all age
groups. If you've got stuff going on in
any of those areas, it may impact your
response to various drugs.
Chronic stress and substance misuse, and
I don't know anybody who doesn't have
one or both of those, chronic stress and
substance misuse accelerate biological
aging, making the body physiologically
physiologically older than the
chronological age. So, you may have a
client who is 45-50 years old, but they
have been under a heap ton of stress for
20 years, and their body is responding
more akin to that of a 60-year-old.
As the body ages, drugs stay longer and
increase in concentration.
As the body ages, we tend to lose muscle
and gain fat whether we want to or not.
One of the reasons that people are
encouraged as they age to engage in
strength training activities, etc., is
to help keep that muscle mass. However,
as we gain more fat,
the fat-soluble drugs tend to be much
more available in our body. For example,
benzodiazepines, these are fat-soluble
drugs. For diazepam specifically, and
your benzos are anti-anxiety
medications. For diazepam specifically,
the half-life increases about 1 hour so
for every year of age. So, a 70-year-old
adult might have a half-life of 70
hours. So, it takes the drug 70 hours to
get halfway out of the body,
essentially. Whereas a 20-year-old,
it only takes 20 hours. You can see how
if you prescribe the same amount for a
20-year-old as a 70-year-old, it's going
to build up in a 70-year-old's body
really fast because they're not clearing
it out. It's just sitting there.
And that can rapidly develop into
toxicity. Likewise, for people who
self-medicate,
we need to make sure that they're aware
of the
effects of aging on their bodies'
response to medication. Not that we want
to encourage them to self-medicate, but
we know it happens.
Water-soluble drugs, and those are your
ACE inhibitors or not your ACE
inhibitors, I'm sorry, your NSAIDs and
other drugs like that.
With aging, total body water decreases
while body fat increases.
Water-soluble drugs distribute into a
into less body water, making a stronger
solution. So, it sits in the body. Think
about if you've ever made
sugar water, maybe for hummingbirds or
something. If you put a half a cup of
sugar to a cup of water, you're going to
get a good strong solution. But if you
put a cup of water to a cup of sugar,
you're actually going to have a solution
that's too strong and it can't hold all
of the all of the sugar. And that's
what's happening when people take
water-soluble drugs.
Common fat-soluble drugs. These are
drugs that build up in the body because
we have more fat and they clear less
quickly. They clear more slowly. Benzos,
your anti-anxiety medications, opioids,
your pain medications, statins, your
anti-cholesterol medications,
beta blockers, those are used for
hypertension,
corticosteroids like prednisone,
antipsychotics, calcium channel
blockers, stimulants including caffeine,
and nicotine.
Being aware that older adults may have a
much slower clearance of all of these.
And people with an older cellularly
older body may have a harder time
clearing these drugs.
Water-soluble drugs include antibiotics,
ACE inhibitors, antihypertensives,
diuretics,
Tylenol, and lithium.
Uh
the one that, you know, we work with in
mental health on this list is more
lithium than anything else. But a lot of
people who have high levels of cellular
aging are probably on antihypertensives
or and/or diuretics and/or Tylenol or
some sort of other analgesic.
As we age,
kidney clearance decreases by
approximately 1%
and liver clearance decreases by
approximately 8% per year after age 40
in healthy, abstinent adults.
Healthy and abstinent. If they're
drinking, if they are unhealthy in some
way, if they've got fatty liver disease,
whatever the the is, there are a lot of
things that can speed up this
deterioration of the kidney and the
liver.