Chapter 32: Osteoarthritis & Gout – Anti-Inflammatory Therapy

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Welcome back to The Deep Dive.

We're here to help you get through complex clinical topics quickly and efficiently.

Today, we're cracking open that essential pharmacotherapeutics text.

We're focusing on two, well, incredibly common conditions, osteoarthritis OA and gout, and our goal really is for you advanced nursing students listening in.

We want to boil down the key pharmacologic principles, you know, the mechanisms, the dosing, those clinical pearls you actually need for practice.

Absolutely.

It's a vital chapter.

OA is the most common joint issue you'll encounter, period, and then gout is the most frequent inflammatory arthritis.

The goals, though, they're pretty similar for both.

Keep patients functional, stop joint damage, ease the pain, and reduce those acute attacks.

Okay, let's dig into OA first.

People often just think wear and tear, right?

But it's more specific.

What's the key change happening in the joint?

Right, it's not just simple wear.

The defining feature really is the breakdown of the articular cartilage, and this is driven by a big drop in proteoglycans.

Think of proteoglycans as giving cartilage its shock absorption.

When they decrease, the cartilage just loses its ability to handle stress.

So the cushion's gone, what happens to bone underneath then?

Well, the bone tries to compensate.

It remodels, thickens up,

but when this new bone grows at the edges of the joint,

that's when you get osteophytes, bone spurs.

Ah, the bone spurs, and they block movement and narrow the joint space you see on x -rays.

Exactly, leads to pain and stiffness.

Okay, before drugs, we always start with non -pharmacologic stuff.

Yeah, like exercise, PT, weight loss, and that weight loss piece is huge, especially for knees and hips.

Obesity is like the biggest modifiable risk factor there.

It has to be the starting point.

Couldn't agree more.

Non -drug therapies are foundational,

but when those aren't enough,

the guidelines now really point towards starting with topical agents first, especially for certain joints.

Topical's first line, for knee and hand away.

That makes sense, less systemic risk, but why not the hip?

It's about depth, really.

The knee and hand joints are closer to the skin surface so the topicals can penetrate well.

The hip joint, though, it's just too deep.

There are real concerns about whether enough drug actually gets into the joint capsule to be effective.

So yeah, generally not recommended for the hip.

Okay, got it.

So the main player here is topical clofenac, the solution, or the gel, same mechanism as oral NSAIDs.

Pretty much, yes.

It inhibits prostaglandin synthesis locally.

The huge advantage is that systemic absorption is minimal, maybe only 6 to 10 % for the gel.

So you get local relief with a much lower risk of those systemic side effects we worry about with oral NSAIDs.

Just remember never unbroken skin.

Crucial point.

What about capsaicin?

That's another topic.

Different mechanism, right?

Involving substance P.

Yes,

exactly.

Capsaicin works by depleting substance P.

Substance P is a key neurotransmitter that sends pain signals from the joint back to the brain.

Now here's the really important clinical pearl for you.

When you first start using it, it often causes burning or stinging.

That's because it first releases substance P before it starts depleting it.

So it gets worse before it gets better.

Kind of, yeah.

And patients need to know this.

They need to stick with it.

The maximum pain relief usually takes like 2 to 4 weeks of continuous use.

Okay, that's a critical counseling point.

If they stop early because it burns, they miss the whole benefit.

Good to know.

Alright, shifting to oral meds.

NSAIDs.

Still a cornerstone but complex.

You mentioned a dual mechanism.

That's right.

Two main things happening.

First, the classic action.

They block the conversion of arachidonic acid into prostaglandins.

That's the main anti -inflammatory bit.

The second and sometimes overlooked, especially at higher doses, they seem to interfere with protein kinase activation too, which adds to the pain relief.

And the big issue with NSAIDs is always the risk profile tied to KEO -X selectivity.

Can you break down KEO -X1 versus KEO -X2 simply?

Sure.

So KEO -X1 is generally considered the housekeeping enzyme.

It's protective in the stomach lining, helps with kidney function, platelet function.

Kind of a good guy, mostly.

KEO -X2 is the one that gets ramped up at sites of inflammation.

So that's the one we ideally want to target to reduce inflammation and pain.

But, and this is important, KEO -X2 is also found normally in the kidneys.

So inhibiting either KEO -X1 or KEO -X2 can potentially harm kidney function.

Which brings us squarely to the black box warnings.

First, the GI risk bleeding, ulcers, perforation, serious stuff.

For patients at high risk, say over 65 or with a history of PUD, peptic ulcer disease, what do we have to do?

For those folks, you absolutely need to add a protective agent.

Usually that means betelprostol, which is a synthetic prostaglandin, or more commonly now a PPI, a proton pump inhibitor, like omeprazole.

And the data is pretty clear.

PPIs are better than H2 blockers for preventing NSAID -induced ulcers.

Okay.

PPI protection for high -risk GI patients.

Then there's the other black box warning.

Cardiovascular risk?

MI?

Stroke?

Also very serious.

Extremely serious.

All NSAIDs, except maybe aspirin, carry this warning.

And they're absolutely contraindicated for pain right after CBG surgery, coronary artery bypass grafting.

When you have to use one, the thinking is, well, naproxen seems to have maybe the lowest CV risk profile.

Dekofenac, on the other hand, consistently shows increased risk.

So the mantra is lowest effective dose, shortest possible time.

Exactly.

Lowest dose, shortest duration.

And you might need to try a couple different NSAIDs because patient response can really vary.

Okay.

What about acetaminophen, apapetilenol?

Mechanism is thought to be more central COX inhibition.

But the guidelines seem all over the place on this one.

ACR and EUR say conditionally recommended, but ORSI says not recommended.

That's confusing.

It really is confusing for practitioners.

Creeler leaned towards it because, well, it's cheap, it's available, and if used correctly, it's relatively safe compared to NSAIDs.

ORSI, however, points to studies showing, frankly, questionable effectiveness for OA pain and highlights the very real risk of liver damage, hepatotoxicity, especially with overdose or in certain patients.

Right.

So regardless of the efficacy debate, the dosing is non -negotiable knowledge.

What are the limits?

For healthy adults, the absolute max is 4 grams or 4 ,000 milligrams per day.

But, and this is critical if someone has underlying liver disease or drinks alcohol chronically, that maximum dose drops significantly.

We're talking maybe 1 ,800 to 2 ,000 milligrams per day.

You have to counsel on that.

Very important distinction.

Okay.

Quickly touching on some other options for OA, tremadol.

Yeah, tremadol.

It's a dual -action weakmyopioid agonist, plus it inhibits norepinephrine and serotonin reuptake.

The upside is it doesn't have the GI or real risks of NSAIDs.

The downside, well, it carries opioid risks.

Respiratory depression, dependence addiction potential.

And deloxetine, an SNRI antidepressant.

Right.

Deloxetine is actually FDA approved for chronic musculoskeletal pain, including OA.

It boosts serotonin and norepinephrine centrally to help modulate pain signals.

You just need to be mindful of its metabolism through CYP enzymes and the potential risk of serotonin syndrome if you combine it with other serotonergic drugs.

Lastly, intraarticular injections.

Steroids.

Steroid injections.

Yeah.

Good for just one or two affected joints.

They can give pretty rapid symptom relief that might last weeks, maybe months.

The key pearl here is frequency.

To avoid damaging the cartilage further, you really shouldn't inject the same joint more often than about every six months.

And hyaluronic acid injections, still around, but...

Generally not recommended anymore.

The evidence for real benefit is just too limited compared to placebo or even steroid injections.

Okay.

Let's switch gears completely.

Gout.

Inflammatory arthritis caused by crystals.

Monosodium urate crystals because of high uric acid levels.

What's the magic number for high uric acid or hyperuricemia?

The definition we use is a serum urate level greater than 6 .8 milligrams per deciliter.

Above that, the urate can start to crystallize out in the joints and tissues.

And why do people get high uric acid levels?

Is it mostly making too much or not getting good enough?

It's usually the latter under excretion by the kidneys.

This can be due to underlying kidney problems or sometimes medications of the culprit.

Things like phytozyte diuretics or even low dose aspirin -like, less than a gram a day, can interfere with uric acid excretion.

Okay.

So the crystals form.

How do they trigger that incredibly painful attack?

Well, the immune system sees these crystals as foreign invaders.

Macrophages, a type of immune cell, gobble them up, phagocytize them.

And in response, these macrophages release a powerful inflammatory signal, mainly interleukin -1 -beta or IL -1 -beta.

IL -1 -beta.

And what often triggers that release, people talk about alcohol or big meals setting off an attack.

Right.

It seems that IL -1 -beta release needs a sort of second signal.

And free fatty acids often provide that signal.

Alcohol metabolism produces fatty acids.

And large, rich meals, especially those high in purines, which break down into uric acid, can also increase free fatty acids.

So that's the trigger.

Makes sense.

Chronically, gout can lead to tophi, those chalky nodules of crystals under the skin.

But the acute attack is classic, isn't it?

Oh yeah.

Rapid onset, usually in one joint, often the big toe initially, intense redness, swelling, pain, reaching peak inflammation within like 24 hours.

It's brutal.

Okay.

So managing chronic gout, the goal is to lower that serum urate level, right?

Below 6mgDL.

Exactly.

Less than 6mgDL is the target for most patients, sometimes even lower if they have uric acid or tophi.

We do this with urate lowering therapy, or ULT.

But starting ULT can actually cause a flare.

Seems counterintuitive.

Why the need for prophylaxis, like with an NSII or colchicine for the first 6 months?

It does seem odd, but it's because starting ULT mobilizes urate that's already deposited in the tissues.

As these stores break down and uric acid levels shift, it can temporarily trigger crystal shedding and inflammation.

So yes, prophylaxis with low -dose colchicine or an NSAID for about the first 6 months is crucial to prevent those initiation players.

Got it.

Let's talk about the first -line ULT, allopurinol.

It's a xanthine oxidase inhibitor, an XOI.

How does it work?

Xanthine oxidase is the key enzyme in the last step of uric acid production.

It converts precursors, hypoxanthine and xanthine, into uric acid.

Allopurinol simply blocks that enzyme.

So instead of making uric acid, the body makes more hypoxanthine and xanthine, which are much more soluble and easily excreted by the kidneys.

Uric acid levels drop.

Simple enough.

But allopurinol has a really serious potential side effect linked to genetics.

This is major for advanced practice.

It absolutely is.

There's a rare but potentially fatal hypersensitivity reaction, including Stevens -Johnson syndrome or toxic epidermal necrolysis.

And we know this risk is significantly higher in individuals carrying a specific gene variant, the HLA -B5801 allele.

Wow.

So we need to test for this.

Yes.

Testing for HLA -B5801 is specifically recommended before starting allopurinol in certain populations known to have a higher frequency of this allele.

That includes patients of Korean descent, especially if they have stage three or worse chronic kidney disease, and also patients of Han Chinese or Thai ancestry.

And if they test positive.

You absolutely do not use allopurinol.

You have to choose an alternative ULT.

It's a critical safety check.

Huge responsibility.

Okay.

What's the main alternative XOI, fibuxostat?

Fibuxostat is the other XOI.

It works similarly to allopurinol.

However,

its use is really limited now because of post -marketing studies that showed an increased risk of cardiovascular death compared to allopurinol.

Another black box warning.

So fibuxostat is basically reserved for?

Reserved for patients who truly cannot tolerate allopurinol or who don't reach their target uric acid level even on the maximum dose of allopurinol.

It's not a first choice.

Okay.

What if XOIs aren't enough or aren't tolerated?

What's the next step maybe as an add -on?

Then you might consider a uricoceric agent, like probenicid.

Probenicid works differently.

It acts on the kidneys to block the reabsorption of uric acid back into the bloodstream so more gets flushed out in the urine.

But there are limitations there too, right?

Kidney function?

Stones?

Definitely.

You need decent kidney function for it to work.

So it's generally contraindicated if the cratinine clearance is less than 50 MLME.

And because it increases uric acid in the urine, you wouldn't use it in someone with a history of uric acid.

Kidney stones could make things worse.

Makes sense.

And the last resort for really tough refractory gout, that IV drug?

Right.

Paglotticase.

It's an IV infusion, very expensive.

It's basically a recombinant version of an enzyme called uricase, which humans don't naturally have.

Uricase breaks down uric acid directly into a harmless, easily excreted substance called allantoin.

It's very effective at lowering uric acid.

But it comes with risks.

Another black box?

Yes.

A black box warning for infusion reactions in anaphylaxis.

It's a foreign protein, so the body can react strongly.

That's why it absolutely must be given in a monitored healthcare setting, usually with pre -treatment medications like antihistamines and steroids.

Okay.

That covers chronic management.

Now, treating the acute flare itself.

Lightning -fast attack.

What are the go -to options, started within 24 hours?

You've got three main choices for first -line therapy in mild to moderate attacks.

NSAIDs, systemic corticosteroids, or colchicine.

And the text specifically mentions naproxen, endomethacin, and sullendak as NSAIDs commonly used for acute gout flares.

Okay.

Corticosteroids like prednisone.

Usually a short burst.

Yeah.

A short course, maybe five to 10 days, to quickly knock down the inflammation.

Tapering isn't usually needed for such short bursts.

Intraarticular steroid injection is also great option if it's just one or two easily accessible large joints involved.

Very effective.

And then there's colchicine again, used acutely too.

Mechanism is anti -inflammatory.

Purely anti -inflammatory for the acute flare.

It interferes with microtubule function and neutrophils, which kind of paralyzes them and stops them from migrating to the joint and gobbling up crystals, reducing inflammation.

And the dosing for an acute attack is really specific, isn't it?

We need to get this right.

Absolutely critical.

The FDA approved regimen is 1 .2 milligrams taken immediately at the first sign of a flare, followed by 3 .6 milligrams one hour later.

That's it.

Total 1 .8 milligrams.

And crucially, this needs to be started within 36 hours of the flare onset to be really effective.

The old higher dose regimens cause way too much toxicity.

Okay.

1 .2 milligrams and 0 .6 milligrams an hour later, within 36 hours.

Got it.

Now, this leads to probably the most critical drug interaction we've discussed, colchicine's danger Yes.

This is life or death stuff, potentially.

Colchicine is metabolized primarily by the liver enzyme CYP3A4.

It's also transported out of cells by peak lycoprotein or PGP.

If a patient takes colchicine concurrently with a drug that strongly inhibits either CYP3A4 or PGP.

Like certain antibiotics, antifungals, or some HIV meds like cobicistat mentioned in one of the cases.

Exactly.

Those inhibitors block colchicine's breakdown and elimination.

Levels skyrocket in body.

And because colchicine inhibits cell division, high levels become systemically toxic.

It can lead to multi -organ failure, bone marrow suppression, muscle breakdown, kidney failure, liver failure.

It can be fatal.

Wow.

So you absolutely must check for interacting drugs, especially strong CYP3A4 inhibitors before prescribing colchicine.

Without fail.

Yeah.

Every single time.

If a strong inhibitor is necessary, the colchicine dose needs to be drastically reduced or more likely avoided altogether during that period.

Patient safety depends on it.

Hashtag outro.

Okay.

That was intense.

A really deep dive into two very different, but common conditions.

OA, meeting that multi -step approach, often starting topical.

Right.

Minimizing systemic risk first.

And GOUT demanding those urate lowering therapies for chronic control, but with really complex risks.

GI, CV, and that critical HLAB5801 genetic screening piece for allopurinol.

And for you, the advanced practitioner,

remember monitoring is key.

LFTs for APAP and XOIs, CBC and kidney function for long -term NSAIs.

Plus patient education is paramount.

Explaining those black box warnings, the strict APAP dose limits, and especially that potentially lethal colchicine interaction with CYP3A4 inhibitors.

So here's something to think about as you move forward.

We talked about the conflict around acetaminophen for OA, ACR, kind of recommends it.

OISI says no.

Questionable efficacy.

It really highlights a core challenge, doesn't it?

How do you balance safety, cost, and sometimes conflicting evidence when you're making these crucial medication choices for your patients?

Something to really chew on.

Definitely.

Well, thank you for tuning in and taking this deep dive with us today.

We hope it was helpful.

Yeah, absolutely.

We wish you all the best as you continue learning.

We'll catch you on the next deep dive.