Chapter 10: Drug Therapy in Geriatric Patients

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Imagine you spend years, I mean literally years, mastering the operating manual for this highly complex machine.

You know what happens when you press every button, how much fuel it needs and exactly how it's going to respond.

Right.

You've got it completely dialed in.

Exactly.

But then, decades later, the internal wiring of that machine just slowly starts to change.

The fuel lines narrow, the filters slow down, and suddenly your old operating manual is completely unreliable.

It's a great analogy.

Because when it comes to pharmacology, that changing machine is the human body as it ages.

Right.

And here's the wild part.

Older adults make up just 12 .8 % of the U .S.

population, but they consume a massive 33 % of all prescribed drugs.

It's just a profound imbalance.

I mean, we are dealing with a population that is highly medicated, yet physiologically they are the most unpredictable in how they actually process those very medications.

Welcome to the Deep Dive.

Today, we are taking the complex pharmacology of the aging body from Chapter 10 of Lens

Pharmacotherapeutics, and we're translating it into a real -world clinical framework for you.

Yeah.

We're going to map out how aging bodies actually process drugs.

We'll look at how to anticipate adverse reactions, how to navigate the psychology of getting your patients to actually take their meds, and ultimately how to manage end -of -life care.

Think of us as two seasoned colleagues just sharing the insider clinical secrets that catch even veteran prescribers off guard.

For sure.

But before we get into the weeds,

what's the mindset we need to be in?

As we navigate this, I want you to keep one overarching clinical mindset at the forefront.

In geriatric pharmacotherapy, our primary objective frequently shifts.

Shifts how?

We move away from the aggressive pursuit of curing chronic incurable illnesses, and instead we focus heavily on reducing symptoms and improving the patient's quality of life.

So it's less about fixing and more about managing.

Exactly.

It's a subtle but really vital recalibration for any clinician.

Okay, so let's start at the very beginning of the pharmacokinetic journey.

Absorption and distribution.

A drug enters the body.

What physically changes as we age?

So looking at absorption first, the overall percentage of an oral dose that ultimately gets absorbed, that usually doesn't change much.

Oh really?

I would have thought it dropped.

You'd think so, but no, the percentage stays stable.

But the rate of that absorption definitely slows down.

Gastric emptying is delayed,

and splanchonic blood flow, the blood flow to the gut, is significantly reduced.

Okay, so the drug still gets into the systemic circulation, but it might take much longer to see the actual therapeutic response.

Right, but there is one major exception to that rule about the percentage staying the same.

Which is?

Gastric pH.

Older adults naturally produce less stomach acid, meaning their baseline gastric pH is higher.

Ah, okay.

So if you prescribe a medication formulation that strictly requires a highly acidic environment to dissolve,

like certain calcium supplements or antifungal medications.

Yeah, that drug is going to struggle to be absorbed at all.

That is a critical catch.

But I feel like where the clinical picture gets truly fascinating is in distribution.

Oh, absolutely.

When we look at body composition in aging, there are four major physical shifts we really have to account for.

Right, let's break those down.

We see an increase in body fat, a decrease in lean body mass, a decrease in total body water, and a decrease in serum albumin levels.

I love visualizing this because it makes the hidden pharmacology so obvious.

Like, think about that increased body fat.

It acts like a giant sponge.

It really does.

So if you prescribe a highly lipid -soluble drug like the beta blocker propranolol, that excess fat tissue just soaks it up and traps it.

It essentially creates an internal storage depot.

Right, and because the drug is trapped in the fat, there's less of it actually circulating in the blood.

Which means you get a visibly reduced clinical response.

Exactly, and the inverse happens with water -soluble drugs, which is equally dangerous, honestly.

Yes, because older adults have decreased total body water and decreased lean muscle mass.

So introducing a water -soluble drug ethanol is a classic pharmacological example here.

It's like putting a single drop of concentrated dye into a tiny shark glass of water instead of a giant pitcher.

That's a perfect way to put it.

The overall volume of distribution is much smaller.

So the concentration of the drug spikes and the physiological effects become intensely magnified.

Building on that, the fourth shift decreased serum albumin is a massive blind spot for prescribers.

Why is that?

Well, in healthy older adults, albumin might only be slightly reduced.

However, in older adults who are malnourished or acutely ill, albumin levels drop significantly.

Let's make sure we clarify this for everyone listening, because understanding this mechanism literally prevents overdoses.

How does malnutrition directly lead to a drug overdose effect?

Think of albumin molecules as transport shuttles in the bloodstream.

Many drugs are chemically designed to bind tightly to these shuttles.

Only the drug molecules that are left free or unbound in the plasma are actually active and able to trigger a response at the cellular receptor.

So if your patient is malnourished and have low albumin, there are simply fewer shuttles available.

Suddenly, drugs that are normally highly protein -bound have nowhere to park.

Wow.

So the levels of free active drug in the bloodstream just skyrocket even if you gave them a completely standard dose.

Exactly.

That rising level of free drug can quickly cross the threshold into toxicity.

The effects become dangerously intense, all because of a missing protein in the blood.

Okay, so we've absorbed the drug, we've distributed its sponges and shot glasses and missing shuttles.

Now the body has to break the drug down and clear it out.

Let's look at metabolism and excretion.

So metabolism primarily happens in the liver, right?

And hepatic rates steadily decline as we age.

Right.

That's because it reduced hepatic blood flow, a smaller overall liver mass,

and decreased activity of hepatic enzymes.

Meaning the liver is just working at a really sluggish pace, the half -life of certain drugs increases, and they stay in the system longer, which prolongs the responses.

But the real danger here has to be the drop in first -pass metabolism, right?

Without a doubt.

Normally, oral drugs are heavily filtered and inactivated by the liver before they ever reach the systemic circulation.

But because that filtration system is sluggish in older adults.

Yeah, an oral drug might slip past the liver entirely and enter the bloodstream at unexpectedly high potent levels.

Which brings us to the other end of the elimination process excretion.

And the text points out this is widely considered the single most important cause of adverse drug reactions in older adults.

It is.

The kidneys are taking a massive hit.

They really are.

You have reduced renal blood flow,

a lowered glomerular filtration rate,

decreased active tubular secretion,

and literally fewer functional nephrons.

So if a drug is eliminated primarily by the kidneys and those kidneys are failing, the drug just accumulates in the body until it reaches toxic levels.

As a clinician, checking kidney function before prescribing is totally non -negotiable.

But there is a massive clinical decision -making trap here that catches a lot of folks off guard.

The serum creatinine trap.

Yes.

You are taught to rely on serum creatinine levels as the everyday go -to lab for kidney health.

But in geriatric pharmacology, relying on a quote -unquote normal serum creatinine result can be catastrophic.

Let's break down why.

Let me think about this.

Creatinine is a byproduct of muscle breakdown.

It comes from lean muscle mass.

But we just established that older adults lose their lean muscle mass.

You've just hit on the exact mechanism of the trap.

Because older adults naturally lose lean muscle mass, their bodies are producing much less creatinine to begin with.

Oh, wow.

So their kidney function could be absolutely terrible, like their nephrons aren't filtering anything at all.

But because they don't have the muscle mass to produce the creatinine in the first place, the blood test looks totally normal.

Right.

The serum creatinine level effectively masks the renal decline.

You could look at that normal lab result, confidently prescribe a standard dose of a cleanly cleared drug, and essentially poison your patient because they have no physiological way to excrete it.

That is terrifying.

So what is the proper metric to keep our patients safe?

You have to look at creatinine clearance, or the estimated glomerular filtration rate, the EGFR.

How do you get that?

You calculate this using tools provided by organizations like the National Kidney Foundation.

Those calculators factor in age, weight, and sex, giving you a true, accurate picture of renal clearance.

That is a clinical secret you want to sear into your brain.

Okay, so we've mapped how the drug gets to the target.

Let's talk about pharmacodynamics.

What happens when the drug actually reaches the cellular receptor?

While our scientific knowledge here is still somewhat limited to specific drug families, we know definitively that receptor properties themselves change with age.

Beta blockers are a great example of this, right?

Yeah, they target beta -edrenergic receptors in the heart, but they actually become less effective in older adults, even if the concentration of the drug in the blood is exactly the same as in a younger person.

And the underlying pathophysiology there is likely a reduction in the sheer number of beta receptors, or a reduction in how tightly those receptors bind to the drug their affinity.

Exactly, but then it flips the other way, too.

Right.

Drugs like warfarin and certain central nervous system depressants become far more intense in older adults, implying their target receptors might increase in number or affinity.

It's tricky.

I have to push back here on behalf of the listener, though.

I mean, if the very rules of pharmacodynamics are changing invisibly at the cellular level, and we can't even predict which way the pendulum will swing, how can a clinician possibly anticipate a patient's response?

It's incredibly frustrating, and the honest clinical answer is you can't always predict it perfectly.

So what do you do?

That is exactly why strict, vigilant monitoring for adverse drug reactions is the only safety net you have.

You essentially have to assume the physiological response will be atypical until proven otherwise.

Okay, let's talk about those adverse drug reactions, or ADRs, and establish a safety baseline.

The scoop of this problem is staggering.

It really is.

ADRs are seven times more common in older adults.

Seven times.

Yeah.

And they account for 16 % of hospital admissions in this demographic, and an astounding 50 % of all medication -related deaths.

But identifying an ADR in this population is uniquely difficult because the symptoms are notoriously nonspecific.

Like what?

Well, you aren't always looking for a textbook rash or an acute anaphylactic crisis.

You are looking at a sudden dizzy spell, a loss of appetite, or a gradual cognitive impairment.

Which you're so easily brushed off and misdiagnosed as just normal aging or the onset of dementia.

Exactly.

And there's a cultural layer we have to navigate, too.

Generational taboos might prevent older adults from disclosing alcohol or recreational drug use.

Which completely obscures your ability to figure out why a new dangerous symptom is happening.

No, it requires deep clinical curiosity.

It's crucial to understand that these ADRs are rarely just a symptom of aging itself.

The root causes are systemic.

It's the drug accumulation from the renal decline we just covered.

It's polypharmacy patients trying to juggle 10 different medications at once.

And it's the presence of multiple severe comorbidities interacting.

It's also the use of drugs with a narrow therapeutic index, like digoxin for heart failure, where the line between a helpful dose and a toxic dose is razor thin.

Plus, importantly, most of these ADRs are dose -related.

They aren't random idiosyncratic allergies.

They are happening because the dose is simply too high for the patient's altered physiology.

Okay, so this gives us our safety priorities.

Take exhaustive drug histories, including over -the -counter medications and herbal supplements because those interact constantly.

Simplify the daily regimen as much as humanly possible.

Actively encourage patients to dispose of their old medications so they don't accidentally take a drug you discontinued a year ago.

And the ultimate prescribing mantra for geriatrics, start low and go slow.

A cliche because it saves lives.

Truly.

So we know the risks.

Now, how do clinicians systematically avoid writing dangerous prescriptions?

We use industry standard frameworks like the Beer's Criteria and the StopPee Start Criteria.

Right.

The Beer's List identifies drugs with a high likelihood of causing adverse effects in adults over 65.

The rule of thumb is to avoid these drugs unless the clinical benefits heavily, demonstrably outweigh the risks.

And the StopPee Start Criteria is a brilliant companion tool.

StopPeePee stands for a screening tool of older people's potentially inappropriate prescriptions.

It flags what to stop, but the start part actually flags appropriate treatments you should be initiating, ensuring we aren't withholding beneficial treatments just because someone is older.

I love that.

Let's do some dynamic clinical reasoning here using the tables from the text.

Let's say my older patient has moderate chronic pain.

My instinct might be to reach for a strong NSI, like endomethacin or Ketrolac.

Right.

But knowing what we just discussed about how compromised their kidneys are, that feels like a massive trap.

Your instinct is spot on.

Both are heavily flagged on the Beer's List.

Chronic use of those NSI's carries a huge risk for gastrointestinal bleeding and acute renal failure.

Ouch.

Plus, endomethacin specifically has a higher risk of central nervous system effects like confusion.

What if I pivot to Mepyridine for more severe pain?

You still want to avoid it.

It's not highly effective at usual doses in older adults, and it carries a massive risk for neurotoxicity, severe confusion, and delirium.

So what's the alternative?

Instead, for mild pain, look to acetaminophen or short -term, very low -dose NSAIDs.

For severe pain, the pivot is usually to morphine.

Makes sense.

Let's look at depression.

Say I'm looking at tricyclic antidepressants, like amitriptyline.

Okay.

Knowing that older adults often struggle with drying out, constipation, and urinary retention, I'm guessing the heavy anticholinergic effects of TCA's make this a terrible idea.

A major red flag.

TCA's, like amitriptyline, will cause severe constipation, urinary retention, and blurred vision.

Oh, wow.

Worse, they cause orthostatic hypotension and syncope fainting.

A fainting spell leads to a fall, and a fall on a geriatric patient can be fatal.

Right, so you wanna switch to an SSRI with a shorter half -life.

Exactly.

What about a patient who just needs help with seasonal allergies or sleep?

Can I just tell them to take some over -the -counter benadryl, which is diphenhydramine, a first -generation antihistamine?

Absolutely not.

First -generation antihistamines are also highly anticholinergic.

They cause profound sedation and urinary retention, always opt for a second -generation antihistamine like cetirizine.

Good to know.

Let's talk hypertension, an alpha -1 blocker.

Again, high risk for orthostatic hypotension.

When they stand up, their blood pressure plummets, they get dizzy, and they fracture a hip.

Use a thiazide diuretic or an ACE inhibitor instead.

How about sedative hypnotics for severe insomnia or anxiety?

Barbiturates or long -acting benzodiazepines like diazepam?

Major fall and delirium risks they cause profound cognitive impairment, physical dependence, and paradoxical reactions.

So what do we do instead?

Pivot to a low -dose rammel tie -in, or better yet, avoid the pharmacy altogether and prescribe cognitive behavioral therapy.

Two more quick ones to flag.

Muscle relaxants are generally out because they are highly anticholinergic and cause intense sedation.

Right.

And long -term use of proton pump inhibitors, or PPIs, are flagged because they increase the risk of C.

diff bacterial infections and bone fractures.

Yeah, that's a big one.

And warfarin, the classic blood thinner.

Warfarin was recently flagged because the bleeding risks now widely exceed the benefits compared to newer options.

Yeah, for anticoagulation today, the standard of care is shifting to direct oral anticoagulants, like apixabam, which are much safer and require less monitoring.

Okay, I have to ask a real -world clinical reality question here.

If I inherit a 66 -year -old patient

who has been taking one of these bad beers list drugs, say,

amitriptyline safely and effectively for 10 years, do I just rip them off of it today because a list told me to?

This is where the art of clinical nuance comes into play.

No.

If the drug is actively meeting the patient's therapeutic needs, and it is demonstrably not causing adverse side effects, it is illogical to abruptly start it based on their chronological age alone.

Okay, that's a relief.

You weigh the benefits and risks for the specific unique individual sitting in your exam room.

We aren't treating a textbook, we're treating a person.

Which leads us perfectly into the great adherence puzzle.

Oh, yeah.

You can master the beers list and write the absolute perfect, safest prescription in the world, but it is totally useless if the patient doesn't actually take it.

The reality of nonadherence is staggering.

Between 26 % and 59 % of older adults fail to take medicines as prescribed.

Which leads to an estimated $100 billion a year in hospital admissions and avoidable complications.

And the vast majority of this, 90 % of it is underdosing, not overdosing.

They just aren't taking the pills.

The unintentional reasons are heartbreaking, but totally understandable.

They have multiple chronic disorders, so the daily regimen is confusing labyrinth.

They have cognitive or visual decline.

Right.

Or the packaging is too hard to open for hands crippled by arthritis.

Or, quite simply, they cannot afford the copay.

Those are massive systemic barriers.

But what's truly fascinating, and what often blindsides new clinicians, is that 75 % of nonadherence in this population is completely intentional.

75%.

They are purposely, actively choosing not to take the medication.

Why?

Why would they do that?

It usually comes down to a deeply held personal conviction that they simply don't need the drug, or they believe the prescribed dose is too high.

They might hate the unpleasant side effects, or they are trying to stretch out the pills by taking them every other day because of the sheer expense.

So we're putting all this clinical effort into easy open bottles and large print labels.

And meanwhile, the patient is just sitting there thinking, I can read it fine, I'm just not taking it because it costs as much as my car payment.

Exactly.

How do we fix this?

For the unintentional nonadherence, we can do a lot.

We simplify the regimen to once a day dosing.

We prescribe liquid forms if they have dysphagia and can't swallow pills.

We ask the pharmacy for non -childproof containers.

We also need to actively ask if they can afford the medication rather than waiting for them to volunteer that deeply uncomfortable and embarrassing information.

For sure.

But you're absolutely right.

For that 75 % who are intentionally nonadherent, a large print label won't change a thing.

If they don't believe they need it, they won't swallow it.

For those patients, the only effective intervention is intensive, respectful education.

You have to sit down, take off the white coat metaphorically, and explain the why behind the prescription.

You have to validate their genuine concerns about side effects and try to find a collaborative compromise that keeps them safe.

Empathy as a targeted clinical tool, I love that.

Okay, we're in the homestretch now.

End of life care.

What happens when the ultimate clinical goal shifts away from managing disease and flips entirely to providing palliative comfort?

The fundamental rules of pharmacology, we just spent this whole deep dive learning, they completely flip.

Wait, really?

Yes.

Priority treatment changes entirely.

Drugs that were once considered absolutely vital for long -term health -like statins for cholesterol management are discontinued.

Wow.

And drugs that we just explicitly said were highly inappropriate due to age and risk -like heavy central nervous system sedatives become the central compassionate feature of care.

Okay, let's break down how we manage specific symptoms when comfort is the only goal based on the text guidelines.

First, a pain.

At the end of life, concerns about physical dependence or addiction are entirely irrelevant.

You do not prescribe pain medication, PRN, or as needed.

So you schedule it.

Yes, you schedule it around the clock to prevent the pain from ever peaking in the first place.

But what about that severe renal and hepatic decline we talked about earlier?

How do we give heavy opioids if their organs are failing and they can't metabolize or excrete them?

We adapt the drug choice.

If both the liver and kidneys are failing, fentanyl is the safest choice for severe pain because of its specific metabolic pathways.

And if it's just the kidneys.

If only the renal function is impaired, methadone is a preferred safer option.

Got it.

Let's talk about constipation.

This is a golden, unbreakable rule of palliative care.

Always, always pair an opioid prescription with a laxative order.

Usually an osmotic laxative like laxulose or polyethylene glycol.

Because opioid -induced constipation is severe, deeply uncomfortable, and essentially guaranteed, right?

Exactly.

What about managing delirium?

Well, earlier we established that benzodiazepines cause delirium and falls.

At the end of life, if you try to use benzos to treat delirium, it can actually cause a paradoxical agitation making the patient far more restless and distressed.

So what's the move?

You wanna look for underlying, easily fixable causes like a UTI or urinary retention

or use an anti -psychotic like heliparidol.

Next is dyspnea or severe shortness of breath.

This feels highly counterintuitive for many prescribers.

Opioids are actually a first -line treatment for dyspnea at the end of life.

Opioids for breathing.

Yeah, they reduce the terrifying sensation of breathlessness and ease the physical work of breathing.

Conversely, using standard bronchodilators might just ramp up their heart rate, increase their anxiety, and make the sensation worse.

That is fascinating.

What about nausea and vomiting?

You tailor the pharmacology to the root cause.

If the nausea is from chemotherapy, use a 5 -HT3 antagonist like ondansetron.

And if it's not?

If it's stemming from a bowel obstruction, heliparidol is actually the first -line choice.

Okay, and finally, respiratory secretions.

In clinical settings, this is often referred to as the death rattle, which is an incredibly distressing term to hear.

It is deeply upsetting.

As the patient naturally loses their cough reflex, secretions pool in the airway, creating that sound.

Does it hurt them?

What's crucial to understand here is that expert clinical consensus suggests this rattling does not actually cause physical distress to the dying patient.

But it is intensely traumatizing to the family sitting at the bedside.

So we treat the symptom primarily to comfort the family.

We do.

We use anticholinergics, the very drugs we vehemently avoided on the beers list because they dry things up.

Oh, that makes sense.

Glycopyrrelate is the drug of choice here because it dries those airway secretions effectively but doesn't cross the blood -brain barrier easily, meaning it has fewer central nervous system side effects.

It all comes back to treating the reality of the patient and their loved ones in that specific profound moment.

Always.

We've covered a massive amount of ground today.

We've gone from the cellular level of altered pharmacokinetics, mapped out the systemic traps of excretion, and navigated the profound compassionate decisions required at the end of life.

If there's one final provocative thought I want you to mull over as you step back into the clinic, it's this.

Age is just a number, but physiology is an undeniable scientific reality.

As medical technology continues to rapidly extend our lifespans, pushing the boundaries of human age, we have to ask ourselves a difficult question.

Will the massive pharmacokinetic shifts we've discussed today eventually force the medical community to completely redefine what we consider a normal adult dosage of any new drug brought to market?

That is a fascinating question to grapple with.

The operating manual isn't just outdated.

We might have to write an entirely new one for the future of medicine.

Thank you so much for sitting down and setting with us today.

On behalf of the last minute lecture team, keep questioning the baseline, trust your clinical curiosity, and we'll see you on the next deep dive.