Chapter 24: Antianginal Drugs – Managing Chest Pain

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Welcome back to The Deep Dive.

Today we are taking a focused and really crucial look at

drugs.

That's right.

Our mission is to crack open the core concepts of cardiovascular pharmacology, specifically grabbing the essentials from Lilly's Chapter 24 on meds used for chest pain.

We need to walk through the mechanisms, the risks, and well, the absolutely critical patient safety stuff.

And this isn't just, you know, academic.

We're talking about angina pictoris.

That's the medical term for chest pain.

Right.

And it's the body's main alarm signaling something dangerous,

myocardial ischemia.

Ischemia, lack of oxygen to the heart muscle.

Exactly.

It means there's this critical mismatch where the heart muscle needs more oxygen than the coronary arteries can actually deliver.

Yeah.

It's an immediate life -threatening concern.

Especially given how common ischemic heart disease still is.

Tragically prevalent, yes.

So we have the symptom, the pain, and the immediate problem, the oxygen imbalance.

But what's causing the imbalance usually?

Well, the sources confirm the vast majority of cases.

They stem from coronary artery disease or CAD.

CAD?

That's atherosclerosis.

Usually, yes.

When we talk CAD, we mean those fatty, cholesterol -rich plaques building up.

They harden the arteries, narrow the path for blood.

Okay.

And the pain itself.

Why does lack of oxygen actually hurt like that?

Ah, good question.

You have to understand the physiological.

When the heart muscle is starved for oxygen, it switches gears.

It goes from efficient aerobic metabolism to a kind of desperate, less efficient anaerobic process.

To try and keep making energy.

Right.

But the main waste product from that anaerobic shift is lactic acid.

Like the burn you feel in your muscles after sprinting.

Precisely that feeling.

Yeah.

That buildup of lactic acid, plus other things like bradykinin and adenosine, they irritate the pain receptors around the heart muscle.

So the pressure or burning, it's literally the acid buildup.

It's the muscle basically screaming for help because of that acid buildup.

Okay.

That paints a really clear picture of the cause.

Let's unpack the different types of angina then.

Because treatment depends on knowing which kind we're facing, right?

Absolutely.

There are three classic types clinicians look for.

First up, the most common,

chronic stable angina.

Sometimes called effort angina.

Stable.

Sounds predictable.

It generally is.

It's almost always caused by that fixed atherosclerosis.

And it's reliably triggered by something that makes the heart work harder.

Physical exertion, big emotional stress.

Even things like caffeine or cold weather.

Yes, exactly.

Anything increasing oxygen demand.

The key thing is the pain usually goes away within about 15 minutes with rest or with medication.

Okay.

That sounds manageable, at least compared to the next one.

Unstable angina.

The name alone sounds bad.

It is far more dangerous.

It falls under the umbrella of acute coronary syndrome, ACS.

That's a medical emergency.

Because it's unpredictable.

Unpredictable, yes.

The pain gets worse, more frequent, and crucially, it often happens at rest.

At rest.

Not just with effort.

Right.

If someone suddenly gets severe angina or it rapidly gets worse or more frequent, that's unstable.

And it often leads straight to a myocardial infarction, an MI, a heart attack.

Okay.

So stable is a fixed blockage issue.

Unstable is unpredictable.

Possibly a rupture.

What about the third type?

Vesospastic?

That sounds different.

It is.

Vesospastic angina, also called Prince metals or variant angina.

The mechanism here isn't atherosclerosis.

It's a sudden, intense spasm of the smooth muscle in the coronary artery wall.

So the artery itself just clamps down.

Clamps shut temporarily.

It's weird because it often happens at rest too and sometimes follows a sort of daily pattern.

Knowing those three really frames the treatment goals, doesn't it?

Minimize attacks, improve function, prevent heart attacks.

Yep.

It all comes back to balancing oxygen supply and demand, like Fig 24 .1 shows.

That's the core mission.

Every drug we'll talk about aims to either boost the oxygen supply or cut down the heart's oxygen demand, or sometimes both.

All right.

Let's dive into the drugs.

Three main classes, starting with the vasodilators.

Nitrates and nitrites, like nitroglycerin.

Yes.

Nitroglycerin is the classic prototype.

Isorabidenitrate, isorabidmonotrate, their cousins.

These are the mainstays for both stopping acute attacks and preventing them.

And they work by vasodilation, opening up blood vessels.

Massive systemic vasodilation, yeah.

Relaxing the smooth muscle and blood vessel walls.

They hit all blood vessels, but they have a really big effect on veins.

Okay, hang on.

Why is dilating the veins so important for angina?

Because dilating the veins reduces how much blood actually returns to the heart.

Think of it like easing off the faucet, filling a bucket.

Less blood coming back means less stretch on the heart walls before it pumps.

Ah, less filling volume.

Exactly.

We call that reducing the preload.

Less preload means less work for the heart muscle.

Okay.

Preload down.

What else?

Second, depending on the dose, they also dilate arteries.

This reduces the pressure the heart has to pump against to get blood out to the body.

The resistance it faces.

Right.

It's called afterload.

So reducing both preload and afterload dramatically cuts the heart's workload, its oxygen needs.

And they also dilate the coronary arteries themselves.

Potently.

Which directly increases oxygen supply right to the struggling heart tissue.

So they hit both sides, reduce demand, increase supply.

Makes sense why they're so central.

Now these are used for acute attacks, so timing must be everything.

How fast do they work?

Speed is absolutely critical.

For acute relief, you need the rapid acting forms.

Sublingual tablets, the spray end of the tongue, or an IV drip in the hospital.

How rapid?

Sublingual works in like two to three minutes.

4E is even faster, one to two minutes.

You need that immediate effect.

And the long acting ones, patches, pills.

Those are strictly for prevention.

The patches or extended release pills take maybe 30 to 60 minutes to start working, not for an acute attack.

That difference two minutes versus an hour, that's literally life or death info for a patient.

Absolutely.

Which brings us to that vital patient teaching point about storage for the sublingual Ah yes, the little amber bottle.

It has to be kept in its original tight amber glass container.

Light and moisture wreck the drug incredibly fast.

If someone keeps it in a plastic pill box, or just loose, it might not work when they desperately need it.

And it loses potency over time anyway, right?

It does.

Only good for about three to six months after opening.

Patients need fresh supplies regularly.

Okay, side effects.

Massive vasodilation.

Sounds like it would cause a headache.

Headache is the number one most common side effect, yes.

But clinically, we also watch closely for reflex tachycardia.

Reflex tachycardia.

The heart speeding up in response.

Exactly.

If the blood pressure drops too fast from all that dilation, the body sensors detect it and basically tell the heart, speed up, compensate.

But wait, if the heart speeds up, doesn't that increase oxygen demand?

Kind of defeats the purpose.

That's a sharp point.

It can be a problem.

Sometimes, if that reflex tachycardia is significant, a doctor might add a beta blocker specifically to counteract that speed up, to keep things balanced.

Speaking of balance, what about tolerance?

Can the body get used to nitrates?

It can, and quite quickly.

Sometimes within 24 hours, if used continuously.

That's why we must have a regular nitrate -free period each day.

A break from the drug?

Yeah, usually eight to 12 hours.

So someone with a patch takes it off at night, lets the body's receptors reset, then puts a new one on in the morning.

Prevents tolerance.

And the biggest warning flag,

the absolute do -not -mix interaction.

Cannot stress this enough.

Never combine nitrates with erectile dysfunction drugs.

Sildenafil, Tadalafil, Vardenafil, brand names like Viagra, Cialis, Levitra.

Why not?

Because those drugs are also potent vasodilators.

You combine them with nitrates and the effect adds up.

You can get severe, life -threatening drops in blood pressure.

Cardiovascular collapse.

It's an absolute contra -education.

Non -negotiable patient education.

Wow.

Okay.

Let's shift gears to the second big class.

Beta blockers.

Atenolol, Metoprolol are common examples.

If nitrates are the fast -acting supplied man agents, beta blockers seem more like the methodical demand reducers, especially for exertional angina and after a heart attack.

That's a good way to put it.

Their main target is the beta -1 receptors on the heart muscle itself.

They block the action of stress hormones, catecholamines, like adrenaline.

And blocking adrenaline does what to the heart?

Two key things.

Both negative effects, but clinically beneficial.

First, a negative chronotropic effect.

Chrono, like time.

So slows the heart rate.

Exactly.

Slows the timing, the rate of the heartbeat.

Second, a negative inotropic effect, Eno, relates to force.

So they reduce the force of the heart's contraction.

Okay.

Slower rate, less forceful pump, less work, less oxygen demand.

Makes sense.

But you mentioned something about time being important.

Yes.

This is the really elegant part.

It's not just about slowing the heart down.

By slowing the rate, you significantly increase the amount of time the heart spends in diastole.

Diastole.

The relaxation phase between beats.

Correct.

And diastole is the only time when the coronary arteries, which get squeezed shut during the contraction or systole, can actually fill up with oxygen -rich blood to feed the heart muscle itself.

Ah.

So a slower rate means more filling time for the heart's own fuel lines.

Precisely.

More diastolic time equals more perfusion time for the myocardium.

That's a huge benefit.

And that explains why they're so vital after a heart attack, too.

Definitely.

After an MI, the body is flooded with those damaging catecholamines.

Beta blockers shield the heart from that overstimulation, improving survival odds, and preventing dangerous heart rhythm problems.

Dysrhythmias.

Important drugs.

What about contraindications?

Who needs to be careful?

Two main groups.

First, patients with bronchial asthma.

Even the more selective beta blockers can sometimes hit beta -2 receptors in the lungs.

Causing bronchoconstriction?

Tightening airways?

Potentially, yes.

So caution is needed.

Second, patients with diabetes mellitus.

Beta blockers can hide a key warning sign of low blood sugar.

How so?

Normally, when blood sugar drops too low, hypoglycemia, the body triggers a fast heart rate tachycardia.

That's often the first thing the person notices.

Beta blockers suppress that tachycardia.

So the patient might not realize that their sugar is dangerously low until it's much worse.

Exactly.

It masks that critical warning signal.

Needs careful monitoring and patient education.

Alright, class number three.

Calcium channel blockers.

CCBs.

Amlodipine.

Diltiazem.

Also, frontline drugs for angina and high blood pressure.

Yep.

Very common.

Their mechanism is pretty neat, too.

They block calcium ions from getting into the smooth muscle cells and artery walls.

And calcium is needed for muscle contraction.

It is.

So if you block the calcium, the muscle cell can't contract as strongly.

It promotes relaxation.

Vascular relaxation.

And that relaxation helps angina howl.

Hits both sides again.

It does.

Relaxing the coronary arteries directly boosts oxygen supply to the heart.

Relaxing the systemic arteries all over the body reduces that afterload again.

Less resistance for the heart to pump against.

Right.

Less workload.

Less oxygen demand.

And here's a key thing.

Because they're so good at relaxing smooth muscle, CCBs are particularly effective for that vasospastic angina.

The one caused by artery spasms.

Ah.

Because it directly tackles the spasm mechanism.

Got it.

Now, you mentioned different types of CCBs.

Not all are the same, especially with heart failure.

That's a critical distinction.

You have different subclasses.

Amlodipine, for example, is a dihydropyridine.

Its main effect is powerful vasodilation, opening up blood vessels with relatively little impact on the heart's pumping strength.

Its contractility.

So it's generally safer if the heart muscle is already weak, like in heart failure.

Generally preferred, yes.

But other CCBs, like diltiazum and especially verabimol, are different.

They do have significant negative endotropic effects.

They can noticeably weaken the heart's contraction force.

Which would be bad in heart failure.

Very bad.

If someone already has structural heart issues or a low ejection fraction, meaning the heart pumps out less than about 40 % of its blood with each beat, those potent negative endotropes are contraindicated, could make a heart failure much worse.

Huge clinical point there.

And CCBs have that weird food interaction.

Ah, yes.

The grapefruit juice effect.

Really?

Grapefruit juice?

It sounds strange, but it's real.

Grapefruit juice contains compounds that a key enzyme system in the liver, the cytochrome P450 system, specifically CYP3A4.

And that enzyme breaks down some CCBs.

It metabolizes several drugs, including some CCBs like nifedipine.

If you inhibit the enzyme with grapefruit juice,

the drug doesn't get broken down as usual.

Levels in the blood can soar.

Leading to toxicity, like too much blood pressure lowering.

Exactly.

Increased risk of side effects, potentially dangerous hypotension.

Patients on susceptible CCBs need to be told explicitly,

avoid grapefruit and grapefruit juice.

Okay, that covers the drugs themselves.

But applying this knowledge safely is paramount.

Let's tuck nursing process, the assessments, the safety steps.

This is where the rubber meets the road.

Before giving any anti -anginal, that pre -administration check is vital.

You must take the apical pulse for one full minute.

A full minute, not just 15 seconds, times four.

A full minute.

And hold the dose, notify the prescriber, if the systolic blood pressure is under 100 mmHg or if the pulse is below 60 or over 100 beats per minute.

Why those cutoffs?

A low 100 systolic or below 60 pulse suggests this system might already be too hypotensive or bradycardic to handle more vasodilation or slowing.

Over 100 pulse might indicate that reflex tachycardia or another issue needs addressing first.

And for patients on beta blockers specifically, what's that subtle sign of worsening heart failure we watch for?

Weight Jane.

Keep a close eye on daily weights.

A sudden gain of 1 kg, about 2 .2 lbs, in 24 hours or 2 .3 kg, about 5 lbs in a week that can mean fluid retention.

Meaning the heart isn't pumping effectively, fluid's backing up.

Correct.

It could be an early sign the beta blocker dose needs adjusting or the heart failure is worsening.

Needs reporting ASAP.

Okay.

Implementation.

All these drugs can cause orthostatic hypotension dizziness on standing up.

What's the core safety advice?

Simple but crucial.

Take the medication while sitting or lying down.

That way, if the blood pressure does drop suddenly, they're less likely to fall and get injured.

Makes sense.

And also advise them to avoid things that worsen vasodilation.

Hot tubs, saunas, excessive heat, even too much alcohol.

These can amplify the hypotensive effect.

And changing positions.

Go slow.

Sit on the edge of the bed for a minute.

Dangle the legs before standing up fully.

Give the body time to adjust.

Now for that sublingual nitroglycerin, the acute attack instructions have to be crystal clear.

Absolutely non -negotiable.

Here's the drill.

First twinge of chest pain.

Stop what you're doing.

Sit or lie down immediately.

Take one sublingual tablet or one spray.

Okay.

One dose.

Then what?

Wait 5 minutes.

If the pain is not completely gone after 5 minutes, call 911 or emergency services immediately.

Don't wait.

Call 911 after the first dose if it doesn't work.

Yes.

After that first dose, in 5 minutes.

While waiting for help to arrive, they could take a second dose 5 minutes after the first, and if needed a third dose, 5 minutes after the second.

But no more than 3 total.

Absolutely.

Max 3 doses in about 15 minutes.

And the call to 911 happens if that first dose doesn't fully resolve the pain in 5 minutes.

That's the critical decision point.

Got it.

And one final reminder about stopping the long -term meds, the beta blockers, and some CCBs.

Never ever stop them abruptly.

Especially if they've been taken for a while.

Why not?

Abrupt withdrawal can cause a dangerous rebound effect.

Rebound hypertension, worsening angina, potentially even trigger a heart attack.

The body is adapted to the drug.

So they need to be tapered off slowly.

Always tapered off gradually, under medical supervision.

Never just stopped cold turkey.

So pulling it all together, remember those core mechanisms, right?

Nitrates hit preload and afterload, reducing workload fast.

The vasodilators.

Gata blockers are the demand managers.

Slowing the heart, giving it more time and diastole.

Brewery controllers.

And calcium channel blockers relax vascular muscle, boosting supply, reducing afterload.

And they're key for vasospastic angina.

They're relaxers.

Okay, here's a final thought to ponder.

Think about how crucial patient education on pharmacokinetics really is.

Knowing that sublingual nitro works in 2 minutes, while a patch takes maybe an hour.

Why isn't that just technical detail?

Why is understanding that onset difference literally a life or death piece of information when teaching someone how to handle an acute attack versus just preventing one?

How did that knowledge empower survival?

Thank you for joining us for this deep dive into anti -anginal pharmacology.

Yeah, we really hope this deep dive helps simplify some pretty complex stuff.

Thank you for being a part of our little last -minute lecture family.