Pharmacology · Lipid-Lowering

Statins + Bile Acid Sequestrants

Two weapons. One battle. Your job is to know how they fight and why they work better together.

The Vignette A 54-year-old man with a family history of premature MI comes in for a routine checkup. He is started on atorvastatin plus cholestyramine. His lipid panel:
TC: 280 LDL: 195 HDL: 30 TG: 275

The board will ask: what happens to his lipids? Why take both? When should he take the statin?

↓ Begin

How Statins Work

Tap each step to watch the mevalonate pathway get dismantled.

Think of your liver as a cholesterol factory. It runs 24 hours a day, and the whole operation depends on one critical machine at step 3. Statins walk in and wreck that machine. Here is how the line runs:

Tap each step to unlock it

1
Acetyl-CoA enters the factory
The raw material is Acetyl-CoAA 2-carbon unit. Comes from fat, carbs, and protein breakdown. The universal building block for fats.. Two of these link up to make HMG-CoA (via HMG-CoA synthase). Think of it as attaching two Lego bricks together.
2
HMG-CoA Reductase: the rate-limiting machine
HMG-CoA ReductaseThe enzyme that converts HMG-CoA to mevalonate. MOST ACTIVE at 8pm. Why? Because you eat dinner, your liver gets busy. Take statins at night for this reason. converts HMG-CoA into mevalonate. This is the rate-limiting step of the whole pathway. Statins sit right here and block it.

STATIN BLOCKS HERE
No mevalonate = no cholesterol further down the line
3
Liver senses the shortage, upregulates LDL receptors
Now the liver is running low on cholesterol. Its response: put out more LDL receptors on the cell surface to pull cholesterol from the blood.

LDL RECEPTORS UPREGULATED
LDL (the bad stuff) gets vacuumed out of the bloodstream

This is why statins drop LDL so dramatically: not just blocking production, but actively scooping it out of blood. Dual mechanism. 🔑Statin = Stolen from the blood (LDL receptors pull it out of circulation)
4
Collateral damage: CoQ10 also gets blocked
Here is the catch: the mevalonate pathway also makes Coenzyme Q10CoQ10 is part of the electron transport chain in mitochondria. Essential for muscle cell energy production. When statins block mevalonate, they also reduce CoQ10 synthesis.. Block the pathway, block CoQ10. Less CoQ10 in muscle cells = less energy = muscle pain and weakness (myopathy).

This is why statins cause myopathy and rhabdomyolysis. Check CPK if a patient on statins complains of weakness. If CPK > 10x normal: stop the statin.
Most active at 8pm → take statins at night for maximum effect. (HMG-CoA Reductase peaks when the liver is processing your dinner.)
🔑
Board Trap: Statin Side Effects
Myopathy/Rhabdomyolysis is the big one. Risk increases massively when statins are combined with fibrates (especially gemfibrozil) or niacin. clinical medicine love this combo. If they give you a patient on statin + fibrate with muscle pain and dark urine, it is rhabdo until proven otherwise.

Also watch: statin + azole antifungals (fluconazole) = higher statin levels = more myopathy risk.

How Cholestyramine Works

It never enters the bloodstream. It works entirely in your gut.

Normally, your liver makes bile acids out of cholesterol. These bile acids get released into the gut to help digest fat. Then, crucially, about 95% of them get reabsorbed at the terminal ileum and recycled back to the liver.

Cholestyramine is a giant resin molecule that grabs bile acids in the gut and refuses to let them go.💡Cholestyramine = Cholesterol's thief: traps bile acids so the liver must steal LDL from blood to make more. They get excreted in the stool. The liver, now short on bile acids, has to make more. And the only way it knows how is to pull cholesterol from the blood.

Gut Diagram · Click to add cholestyramine

Liver
Makes cholesterol → converts to bile acids → secretes into gut. Recycling loop is intact. Cholesterol stays high.
Small intestine
Bile acids do their job (fat digestion).  = free bile acids.
95% reabsorbed at terminal ileum and recycled.
Blood / Enterohepatic Circulation
Bile acids return to liver. Loop complete. LDL-R stays at baseline.
📴 Cholestyramine traps bile acids in the gut → liver uses blood cholesterol to make new ones → LDL falls. It never absorbs into the body. Purely gut action.
🔑
Board Trap: Fat-Soluble Vitamin Malabsorption
Cholestyramine binds to everything in the gut, not just bile acids. Fat-soluble vitamins (A, D, E, K) and many drugs get caught in the resin too.🔍ADEK rule: Cholestyramine vacuums up vitamins A, D, E, K. Take vitamins 1 hour before OR 4 hours after. Same timing rule as statins. This is why patients on cholestyramine can develop vitamin K deficiency (bleeding risk) and must take vitamins separately, at least 1 hour before or 4 hours after the drug.

Lipid Panel Simulator

Toggle each drug on or off. Watch how the numbers move.

💊 Atorvastatin
OFF
🧬 Cholestyramine
OFF
TC
280
baseline
LDL
195
baseline
HDL
30
baseline
TG
275
baseline

No drugs active. Baseline lipid panel.

🔑
Board Trap: Cholestyramine + Triglycerides
Bile acid sequestrants can raise triglycerides.🔥TG 500 rule: Bile acid sequestrants raise TG. Contraindicated when TG > 400-500. Above that threshold = pancreatitis risk territory. If TG are already sky-high (>500), avoid cholestyramine. It makes the TG problem worse. This patient has TG of 275. Watch this. That is why statins are the better workhorse here: they also help TG modestly.

The Timing Trap

One question. Classic board setup. What is the right answer?

Your patient is on both atorvastatin and cholestyramine. The pharmacist calls you: "What time should the patient take the statin relative to the cholestyramine?"

This is not about the drug. This is about cholestyramine's binding problem.

A. Take the statin at the same time as cholestyramine
B. Take the statin 30 minutes before cholestyramine
C. Take the statin 1 hour before OR 4 hours after cholestyramine
D. Timing does not matter for this combination

Side Effect Match

Tap a drug on the left, then tap the side effect on the right to match them.

Each side effect belongs to one (or both) drugs. Match them all to win.

💊 Statin (Atorvastatin)
🧬 Bile Acid Sequestrant (Cholestyramine)
Rhabdomyolysis
Vitamin K deficiency
Hepatotoxicity (LFT elevation)
Constipation / GI discomfort
Myopathy / muscle pain
Raises triglycerides
0 / 6 matched
Side Effect Statin Cholestyramine Notes
Myopathy / Rhabdo YES No Check CPK; risk with fibrates + niacin
Hepatotoxicity YES No LFT > 3x → stop statin
Constipation / GI No YES Major reason for non-compliance
Fat-soluble vitamin malabsorption No YES Vitamins A, D, E, K
Raises TG No YES Avoid if TG > 500

The Full Lipid Arsenal

Statins are first line. Know what comes after.

Ezetimibe
Blocks NPC1L1 in gut → prevents dietary cholesterol absorption
LDL: drops 15-20%
e.g. ezetimibe (Zetia)
PCSK9 Inhibitors
Block PCSK9, which normally degrades LDL receptors. More receptors stay up → more LDL removed.
LDL: drops 50-60%
e.g. alirocumab, evolocumab
Fibrates
Activate PPAR-alpha → increase lipoprotein lipase → TG breakdown
TG: drops 30-50%. LDL: variable.
e.g. gemfibrozil, fenofibrate
Niacin (B3)
Inhibits VLDL secretion from liver → less LDL made. Best HDL raiser we have.
HDL: rises most. Flushing side effect.
e.g. nicotinic acid (Niaspan)
Omega-3 FA
High-dose fish oil → reduces hepatic TG synthesis
TG: drops 20-50%.
e.g. icosapent ethyl (Vascepa), omega-3 acid ethyl esters (Lovaza)
🔑
Board Trap: Statin + Fibrate Combination
Adding a fibrate (especially gemfibrozil) to a statin dramatically increases rhabdomyolysis risk. clinical medicine love this. If the vignette has a patient on both and now has muscle pain + dark urine: rhabdomyolysis. Check myoglobin and CPK, not just LFTs.

Flip the Card

Each drug is hiding something. Tap to flip and expose the side effects and board pearls.

💊
Atorvastatin
High-intensity statin
Tap to reveal
Side Effects + Pearls
  • Myopathy/Rhabdo: CPK > 10x normal = stop immediately
  • Hepatotoxicity: LFT > 3x ULN = stop and monitor
  • Blocks CoQ10 synthesis via mevalonate pathway
  • LDL drops 40-50% (high intensity)
  • Take at night (HMG-CoA peaks 8pm)
💢
Rosuvastatin
High-intensity statin
Tap to reveal
Side Effects + Pearls
  • Myopathy risk: lower than atorvastatin at equivalent doses
  • LDL drops 45-55%: most potent statin per mg
  • More water-soluble than atorvastatin (less muscle penetration)
  • Less CYP450 interaction: fewer drug-drug issues
  • Board tip: rosuvastatin = highest LDL reduction
🧬
Cholestyramine
Bile acid sequestrant
Tap to reveal
Side Effects + Pearls
  • Fat-soluble vitamins A, D, E, K malabsorption
  • Raises triglycerides: contraindicated if TG > 400-500
  • Constipation (main reason for non-compliance)
  • Binds warfarin, digoxin, thyroid meds in gut
  • Never absorbs systemically: all gut effects
🎯
Ezetimibe
NPC1L1 blocker
Tap to reveal
Side Effects + Pearls
  • Blocks NPC1L1 in intestinal brush border
  • Cuts dietary AND biliary cholesterol absorption
  • LDL drops 15-20% alone; adds extra 20% on top of statin
  • Minimal side effects (not a systemic drug)
  • Board: statin + ezetimibe = complementary dual-mechanism combo
🌍
PCSK9 Inhibitors
alirocumab, evolocumab
Tap to reveal
Side Effects + Pearls
  • Block PCSK9 protease that degrades LDL receptors
  • More LDL receptors stay on hepatocyte surface
  • LDL drops 50-60%: most powerful class available
  • Injection-site reactions: only notable side effect
  • Board: for FH or statin-intolerant patients
🔥
Niacin (B3)
Nicotinic acid
Tap to reveal
Side Effects + Pearls
  • Flushing: prostaglandin-mediated, blocked by aspirin 30 min before
  • Best HDL raiser available (raises HDL 20-35%)
  • Inhibits VLDL secretion from liver
  • Raises blood glucose: use cautiously in diabetes
  • Contraindicated with peptic ulcer, gout (raises uric acid)

Lipid-Lowering Therapy Decision Tree

From LDL goal to drug selection. Follow the branches.

Hypercholesterolemia Treatment Algorithm
Patient has elevated LDL
or ASCVD risk
First step
What is the ASCVD risk category?
High/Very High Risk Low/Moderate Risk
High-Intensity Statin
atorvastatin 40-80mg
rosuvastatin 20-40mg
Moderate-Intensity Statin
atorvastatin 10-20mg
rosuvastatin 5-10mg
LDL still not at goal?  
Add-on therapy needed?
TG < 400? TG > 400? Statin intolerant?
+ Ezetimibe
blocks gut absorption
Skip Cholestyramine
raises TG further
PCSK9 Inhibitor
alirocumab or evolocumab
If LDL still > goal after ezetimibe
Consider PCSK9 Inhibitor
for FH or very high ASCVD risk
💡 The key decision point is TG level when considering add-on therapy. Cholestyramine is safe when TG < 300 but becomes dangerous above 400-500 mg/dL.

Clinical Images

Xanthomas, labs, and the lipid pathway made visible.

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Scroll horizontally to see all images. Tap to expand.

Rule Out the Drug

One patient. Four drug options. Clues appear one at a time. Tap the drug that gets ruled out by each clue. On the final clue, the pattern flips: tap the drug you would choose.

A patient with high LDL needs a new lipid-lowering drug. Each clue rules one drug out. Keep eliminating until only the right choice is left.

Fibrate
gemfibrozil
Niacin
B3 vitamin
Bile Acid Seq.
cholestyramine
Statin
atorvastatin
Loading clue...

Decision Tree: Choosing Lipid-Lowering Therapy

Primary lipid abnormality drives drug selection. Follow the branches.

Primary lipid abnormality?

Clinical Vignettes

5 patients. All of them on lipid drugs. Let's see if you paid attention.

Medically reviewed by Kaitlyn Cocuzzo, MD and Fatima Ali, DO · Last reviewed June 2026
Bone Wizardry is an independent educational resource for visual learning in the medical sciences. It is not affiliated with, endorsed by, or sponsored by any licensing or examination board, contains no real or recalled examination questions, and does not guarantee any educational or examination outcome.
clinical Walkthrough

clinical Walkthrough

Original clinical vignettes. Shuffled, never-repeat, full explanations for every choice.