Chapter 36: Antihistamines, Decongestants, Antitussives, and Expectorants

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Okay, if you are currently dealing with that scratchy throat, maybe the sniffles that just won't quit and you just generally feel sick, well, you're right there with everyone who's the common cold.

It's pretty miserable, isn't it?

Usually a viral URI, you know, upper respiratory infection,

often it's rhinovirus, sometimes influenza.

And that leads to all the fun stuff, too much mucus, inflammation, and that really annoying nasal congestion.

Exactly.

And it's a classic case where the symptoms really dictate the treatment.

What's interesting is because finding the exact virus is often tricky or just takes too long, our approach isn't really about curing it.

It's what we call empiric therapy.

We're treating what we see the symptoms, not hunting down that specific bug necessarily.

And that's really our mission for this deep dive.

We've gone through the source material to kind of give you a shortcut here, focusing on the four main tools, pharmacologically speaking, for relief, antihistamines, decongestants, antitissives, and expectorants.

Yeah, we're going to break down how each of them works, you know, their mechanisms, and maybe most importantly, the crucial safety things you absolutely have to keep in mind.

Definitely.

But before we even jump into the first drug class, there's a huge safety point we have to hit right from the sources.

Absolutely critical.

Back in 2008, the FDA put out a really strong recommendation.

Over the counter or OTC, cough and cold meds should not be given to kids under two.

Under two years old, that's key.

It is.

This came after a lot of reports, unfortunately, of serious side effects, things like over sedation, even seizures in really young children who got doses that were too high or given too frequently.

So the takeaway is always always check with a health care provider before giving these to very young children.

Please do.

It's just not worth the risk.

Okay, that's a super important baseline for everyone.

First, when they feel a sneeze coming on, antihistamines, H1 blockers.

Right.

But before we talk about the drugs,

what is histamine actually doing in the body that makes us feel so lousy?

Well, histamine is it's really powerful chemical.

It does a lot.

Normally, nerve signals, heart rate, things like that.

Right.

But when you get an allergic reaction or infection, it gets released in large amounts.

And that's the problem.

That's the problem.

It causes some major changes.

Smooth muscles constrict, which can tighten airways in the lungs.

It causes vasodilation.

So blood vessels widen.

And crucially, it increases capillary permeability.

Okay, capillary permeability.

That's the leaky vessel thing, right?

Fluids seeping out into the tissues.

Exactly.

That's where you get the edema, the swellings, runny nose, all those lovely symptoms.

So the goal of these H1 antagonists, the antihistamines, is basically to stop that.

Precisely.

Think of them like blockers on a football team.

They compete with histamine for those H1 receptor spots on cells like mast cells and basophils.

So timing matters.

Timing is key.

If you take the antihistamine early before the histamine binds,

it physically blocks histamine from getting to the receptor and causing all those downstream effects, the vasodilation, the leaky fluids, the secretions.

Gotcha.

Okay, this brings us to something everyone sees on the pharmacy shelf.

The two generations,

you've got your traditional ones like diffenhydramine that just knock you out.

Right, benadryl.

And then the newer ones like loratadine where you can actually stay awake.

Why is huge difference?

That difference is probably the most critical thing to understand about this class.

It all comes down to the chemistry, really.

Okay.

The first generation, we call them traditional or sedating antihistamines.

Diffenhydramine is a classic example.

They're lipid soluble.

Meaning they like fat.

Yeah, essentially.

And because of that, they easily cross the blood -brain barrier, that protective layer around the central nervous system.

Ah, so they get into the brain.

They get into the brain.

So they work peripherally, you know, on your runny nose, but also centrally in the brain.

And that central action is what causes the significant anticholinergic effects and, of course, the sedation.

And because they cross into the brain, they get used for other things too, not just allergies.

Exactly.

They're quite versatile.

People use them for motion sickness, sometimes as a sleep aid, for insomnia, even for Parkinson's symptoms.

Yeah, interesting.

But there's a trade -off.

Look at Diffenhydramine, where it works fast, maybe 15, 30 minutes onset.

But it only lasts about four hours.

So you're taking it multiple times a day.

Right.

Contrast that with the newer non -sedating drugs.

Luradadine, Fexofedadine, Claritin, Allegra.

Okay.

These were designed specifically to avoid that sedation.

They're less lipid soluble.

They work mostly peripherally.

So they don't cross the blood -brain barrier as easily.

Much less readily, yeah.

So you get far fewer of those central nervous system effects, especially sedation.

And the big plus is their duration.

Luradadine might take an hour or two to kick in, but it lasts for 24 hours.

Once a day dosing.

That's a huge compliance booster.

Absolutely.

Much easier for people to stick with.

Okay, that clears things up a lot.

Now, you mentioned anticholinergic effects with the traditional ones.

Let's talk about those side effects.

The dry mouth, the dizziness.

Yeah, the anticholinergic effects are pretty famous.

We often summarize it as drying everything up.

They inhibit the body's secretions, salivary, gastric, tear ducts, bronchial tubes.

So dry mouth, dry nose, dry throat.

Difficulty urinating sometimes, constipation.

Yeah.

All related to that drying action.

And the main complaint, of course, is the sedation and dizziness.

And that drying effect plus the sedation and dizziness is exactly why there's a big warning for older adults with these traditional antihistamines.

Absolutely.

We strongly advise against using them in the elderly.

The risk of confusion, that hangover feeling the next day, the dizziness, it all adds up.

Leading to falls.

Exactly.

An older person gets confused, dizzy.

They're much more likely to fall.

And the potential harm from a fall usually far outweighs the benefit of relieving a minor cold symptom.

Makes total sense.

Okay, so antihistamines block try to dry things up.

But what about that feeling of being completely stuffed up?

Like you can't breathe through your nose at all.

Right.

That's the swelling inside.

And that's where our next category decongestants comes in.

Their job is the stuffiness.

Directly targeting the stuffiness.

The biggest group here are the adrenergics.

They're also called sympathomimetics because they mimic the sympathetic nervous system, your fight or flight response.

Okay.

There are also anticholinergics and intranasal corticosteroids like fluticazone.

But the adrenergics are really the go -to for that immediate stuffy nose relief.

Think oxometazoline like Afrin.

So walk us through how oxometazoline actually works.

What's the mechanism?

It's all about vasoconstriction.

These adrenergic drugs stimulate specific receptors, the alpha adrenergic receptors on the small arterioles, the tiny blood vessels in the lining of your nasal sinuses.

Okay.

When those receptors are stimulated, the blood vessels constrict, they shrink.

This reduces blood flow to the swollen area.

The tissue shrinks down and allows mucus to drain.

Voila, you can breathe again.

Ah, relief.

But here's where it gets tricky, right?

The difference between taking a pill versus using a nasal spray.

Hugely tricky.

Yeah.

This is probably the most important counseling point for decongestants.

It's all about the rote and the risk of rebound congestion.

Rebound congestion sounds bad.

It is.

So oral decongestants, the pills,

work systemically.

They take longer to kick in.

They're generally less potent, but there's virtually no risk of rebound congestion.

Okay.

Topical nasal sprays, on the other hand, give you that rapid localized relief.

Sometimes it feels like it works in minutes.

But, and this is the big but.

Here it comes.

If you overuse them, when the drug effect wears off,

that vasoconstriction reverses and the blood vessels can actually swell up more dramatically than they were before.

Oh, wow.

So it makes the stuffiness worse.

Way worse.

And that traps you in this cycle.

You feel stuffed up again, so you use the spray again for relief, and it just perpetuates the problem.

Dependence.

That's the vicious cycle.

So the absolute critical safety rule for these topical adrenergic sprays.

Use them for no more than three consecutive days.

Full stop.

Three days max.

Got it.

Beyond that, the risk of getting caught in that rebound cycle just skyrockets.

And we also have to remember, even though it's a spray,

some of that drug gets absorbed systemically.

Right.

It doesn't just stay in the nose.

Exactly.

Which is why even nasal sprays can cause systemic side effects.

Right.

Think cardiovascular stimulation, hypertension, palpitations, maybe a headache,

nervousness, tremor.

And those potential systemic effects mean they're definitely not for everyone.

There are contraindications.

For sure.

Patients with narrow angle glaucoma, uncontrolled heart disease, or hypertension, diabetes.

These folks really need to avoid adrenergic decongestants because of those stimulating effects.

Okay.

Good to know.

Let's shift gears to category three.

Antitussives.

For the cough.

Now, coughing is a reflex.

It's supposed to help us clear stuff out.

When should we actually try to stop it?

That's the key question.

We generally only use antitussives or cough suppressants.

When the cough is nonproductive, meaning you're just hacking away, but nothing's coming up.

Like dry, irritating cough.

Exactly.

Or if the cough itself is harmful.

Like imagine someone just had hernia surgery.

You don't want them coughing forcefully and potentially damaging the repair.

Makes sense.

So there are two main types here.

Opioid and non -opioid.

Let's start with the opioids like codeine.

Right.

Opioid antitussives like codeine work centrally.

They directly suppress the cough reflex right where it originates in the brain stem specifically, the cough center in the They also give you a bit of pain relief, algesia, and they have that drying effect, which can be helpful sometimes.

But the big flashing warning signs with opioids.

Dependency, of course.

And the potential for respiratory depression, slowing down breathing.

That's especially dangerous if they're mixed with alcohol or other drugs that depress the central nervous system.

Major caution there.

Definitely.

Okay.

What about the non -opioid choice like dextromethorphin?

It's related to opioids, but it's in tons of OTC products.

Dextromethorphin is really interesting chemically.

It is derived from an opioid and it also acts on the medulla, similar to codeine, to suppress the cough reflex.

But.

But at the recommended doses, it doesn't really cause pain relief or significant CNS depression like codeine does.

So you get the cough suppression without the same level of risk for dependency or respiratory issues.

Though we should mention it has become a of that potential misuse.

And then there's one more non -opioid, benzinatate, that works totally differently, doesn't it?

Completely different mechanism.

Benzinatate, you might know it as teslan pearls.

It doesn't act on the brain at all.

So how does it stop the cough?

It works peripherally.

It basically anesthetizes or numbs the stretch receptor cells in your airways, in the lungs, the pleura.

These receptors normally send the signal to the medulla to trigger a cough when they're irritated or stretched.

So benzinatate stops the signal before it even starts.

Exactly.

It prevents a reflex stimulation right at the source.

Pretty clever.

Okay.

So whether it's opioid or non -opioid, what's the common side effect warning we need to give patients about any anti -tussive?

The big ones are sedation, dizziness, and drowsiness.

They're common across the board.

So you absolutely have to caution patients about driving or doing anything that requires them to be mentally alert until they know how the medication affects them personally.

Safety first.

Okay.

That brings us smoothly to our final category,

expectorants.

These are supposed to help get the phlegm out, right?

Right.

Expectorants are meant to aid expectoration, the act of coughing up and spitting out mucus, by making respiratory secretions thinner and less sticky, easier to move.

And the main player here is guifinesin.

You see it everywhere, like in mucinex.

That's the one.

Guifinesin is pretty much the only expectorant commonly used these days.

Now the source material mentioned that its actual clinical effectiveness is somewhat questionable.

What's the deal with that?

It's so popular.

Yeah, it's a bit of a clinical reality.

While loads of people use it and feel it helps,

well -controlled scientific studies have often struggled to definitively prove that it significantly thins sputum compared to just, say, drinking water.

The theory behind how it's supposed to work is it increases the hydration within the respiratory tract, reflexively stimulating mucus flow and making it less viscous, less thick.

But the hard evidence is a bit debated.

Okay.

So if the drug itself is maybe questionable, what's the single most effective thing a nurse or clinician can tell a patient to do to help thin out those secretions?

Fluids.

Hands down.

Just drink more water.

Drink more water.

Or juice or broth, whatever fluids they can tolerate.

Encouraging fluid intake, aiming for maybe up to three liters or 3 ,000 millimals per day, unless there's a reason not to.

Like heart failure or kidney problems is the best way to help liquefy respiratory secretions.

Water is honestly the best expectorant.

That's a fantastic practical tip.

And it leads us perfectly into our final section, pulling it all together with the nursing process, those critical connections and safety checks.

Right.

For giving any of these cold medications we've discussed, what's the absolute first assessment priority?

Always, always rule out a serious allergic reaction first.

Anaphylaxis needs immediate attention, obviously.

After that, you need really good patient history.

You're screening for those contraindications we mentioned.

Like the glaucoma, the high blood pressure.

Exactly.

And also assessing their respiratory status, especially looking for chronic lower respiratory tract diseases, things like COPD, chronic bronchitis, even asthma sometimes.

Okay, speaking of those chronic lung conditions, let's circle back to that drying problem with the traditional sedating antihistamines.

Why are they potentially so risky for someone with, say, chronic bronchitis?

This is such a crucial point for practice.

Think about it.

Someone with chronic bronchitis already has trouble clearing thick mucus from their airways.

Right.

If you give them a drug that has strong anticholinergic drying effects, what happens?

That already thick mucus becomes even thicker, stickier, more like glue.

Making it possible to cough up.

Exactly.

It can actually occlude airways, make breathing much harder, and even set them up for a secondary infection like pneumonia or cause parts of the lung to collapse.

So for these vulnerable patients, keeping secretions thin and clearable is way more important than just drying up a runny nose.

Wow.

That really highlights the need for careful assessment.

Okay, just a couple of quick implementation reminders for patient education then.

For traditional antihistamines, taking them with food can help?

Yes.

Take with meals to minimize any GI upset.

And for the topical decongestants, the absolute must -know is?

Stick to the three -day maximum.

Avoid that rebound congestion cycle at all costs.

Council them rigorously on proper use.

Got it.

And for antitussives, especially something like codeine, how should they take it for best effect?

Take it at evenly spaced intervals around the clock, not just when the cough feels bad.

This helps maintain a steady level of the drug in the system for continuous suppression, if that's the goal.

And again, warn about drowsiness and driving.

Okay, this has been a really comprehensive deep dive.

We've covered blocking histamine, shrinking swollen nasal passages,

suppressing coughs appropriately, and trying to thin out mucus.

Yeah, we've really hit the key differences, like centrally acting versus peripherally acting drugs, that localized risk of rebound congestion with sprays, and the importance of only using antitussives for those non -productive coughs.

It seems the big picture is always balancing relief with safety.

It really is.

You want to make the patient feel better, but not at the expense of making an underlying condition worse, or ignoring a major safety risk, like that rebound effect or respiratory depression.

So thinking about all these effects, drying things up, maybe stimulating the heart, sometimes making people sleepy, potentially suppressing a useful cough reflex, it leads to a final thought for our listeners to chew on.

Given this complex interplay, how do you as the clinician really strike that right balance?

How do you provide effective symptomatic relief while still respecting and supporting the body's own necessary defense mechanisms, like the cough, especially in those patients who are already prone to having thick, hard -to -clear secretions?

That's the art of it, isn't it?

It requires careful assessment and really individualized decision making.

We hope this discussion helps you think through those mechanisms and considerations for every remedy you encounter.

A warm thank you from the Last Minute Lecture team.

We really appreciate you joining us for this dive into managing common cold symptoms.