Cardiovascular preventionSources checked Sep 18, 2026

The biology behind treatment

How cholesterol medicines work

Different starting points. A shared destination: helping the liver remove LDL from the blood.

Where each medicine acts

Select a family to follow its pathway.

Absorption

Intestine

Absorbs cholesterol
from food and bile

NPC1L1 transporter

Cholesterol
to the liver

Synthesis & clearance

Liver

Makes cholesterol;
takes up circulating LDL

Cholesterol synthesis
HMG-CoA reductasePCSK9 productionLDL receptors
and recycling

LDL uptake
by receptors

Circulation

Bloodstream

LDL particles
carry cholesterol

Fewer circulating LDL particles

Statins · Make less cholesterol

Reduce cholesterol synthesis in the liver

Target: HMG-CoA reductase. Statins inhibit this enzyme. As liver-cell cholesterol falls, the liver increases LDL receptors, which remove more LDL particles from the blood.

Mechanism & side effects

LDL receptors are reusable proteins on liver cells that bring LDL particles inside. These medicines increase their number or availability through different steps. This is a simplified pathway map.

Reading the side-effect notes

A symptom recorded during treatment is not automatically caused by the medicine. Placebo comparisons help identify an excess, but do not always reveal why it happens. The examples below come from different medicines, populations and follow-up periods; they cannot be used to rank safety across classes.

These are selected class-level patterns, not complete prescribing information. Risks depend on the specific medicine, dose, other treatments and the person taking it. Discuss new symptoms or treatment changes with a clinician; trouble breathing or sudden face or throat swelling needs urgent care.

01Make less cholesterol

Statins

Atorvastatin, rosuvastatin and simvastatin

The normal pathway

The liver makes cholesterol through a sequence of chemical reactions. HMG-CoA reductase controls an important step in that pathway.

What the medicine changes

Statins inhibit this enzyme. As liver-cell cholesterol falls, the liver increases LDL receptors, which remove more LDL particles from the blood.

Statins share this core mechanism, but differ in potency, metabolism and drug interactions. A shared mechanism does not make every dose or medicine equivalent.

Explore therapiesAtorvastatin Rosuvastatin Simvastatin Ezetimibe + simvastatin

Commonly reported effects

Muscle aches and digestive symptoms are reported. The digestive pattern varies by medicine: diarrhea or nausea with atorvastatin, for example, and constipation or nausea with rosuvastatin. Most muscle symptoms reported during statin treatment are not caused by the statin.

Why they may happen

There is no single established explanation for ordinary muscle aches. Higher doses and interactions that raise statin exposure can increase the risk of muscle injury.

Other important risks

Small blood-glucose increases can bring some people near the diabetes threshold across it. Serious muscle injury, including rhabdomyolysis, and serious liver injury are uncommon but important risks, distinct from ordinary aches.

What placebo comparisons show

A 2022 individual-participant meta-analysis of large blinded randomized trials found about 11 additional reports of muscle pain or weakness per 1,000 people during the first year, with little excess overall thereafter, although a small excess may persist with more intensive regimens. This is the treatment-related excess, not the total number of symptoms.

Medicine- and study-specific examples; not a safety ranking.

Sources

Lipitor prescribing information Crestor prescribing information CTT: muscle symptoms in blinded trials (2022) CTT: blood glucose and diabetes (2024)

02Preserve LDL receptors

PCSK9 antibodies

Evolocumab and alirocumab

The normal pathway

LDL receptors on liver cells can be reused after bringing LDL inside. PCSK9 binds to these receptors and promotes their breakdown instead of recycling.

What the medicine changes

These injected antibodies bind circulating PCSK9 and stop it from binding LDL receptors. More receptors remain available to clear LDL from the blood.

Evolocumab and alirocumab share this mechanism. Inclisiran targets the same pathway by reducing PCSK9 production; it is not an antibody. Other ways to target PCSK9 should not inherit antibody-specific safety assumptions.

Explore therapiesEvolocumab Alirocumab

Commonly reported effects

Injection-site soreness, redness, itching or swelling can occur. Cold-like symptoms and aches are also reported; the particular symptoms and differences from placebo vary between the two medicines.

Why they may happen

A local response to the injection or formulation is a plausible explanation for injection reactions. The labels do not establish why respiratory symptoms or aches occur, or that each reported symptom is caused by blocking PCSK9.

Other important risks

Serious allergic reactions, including angioedema (swelling beneath the skin), can occur. These are separate from ordinary local injection reactions.

What placebo comparisons show

Examples from adult hypercholesterolemia trials: injection reactions occurred in 7.2% with alirocumab versus 5.1% with placebo across nine trials (median exposure 65 weeks), and 5.7% with evolocumab versus 5.0% with placebo in one 52-week trial. These are separate studies, not a head-to-head comparison.

Medicine- and study-specific examples; not a safety ranking.

Sources

Repatha prescribing information Praluent prescribing information

03Preserve LDL receptors

Inclisiran

PCSK9 RNA silencing · Inclisiran

The normal pathway

Liver cells use messenger RNA as instructions for making PCSK9 protein.

What the medicine changes

Inclisiran is a small interfering RNA (siRNA) delivered to liver cells. It guides the breakdown of PCSK9 messenger RNA, so less PCSK9 is made and more LDL receptors remain available.

This acts before the protein is produced, whereas antibodies block the protein after it is made. RNA silencing does not edit DNA. Shared LDL lowering does not by itself establish identical cardiovascular benefits.

Explore therapiesInclisiran

Commonly reported effects

Injection-site pain, redness or rash is the clearest common effect. Joint pain and bronchitis were also reported, with smaller differences from placebo.

Why they may happen

A local response to injection or formulation is plausible. The trials do not establish that RNA silencing itself explains joint pain or bronchitis.

Other important risks

Serious allergic reactions, including anaphylaxis and angioedema, have been reported after approval. Those reports do not provide a reliable frequency.

What placebo comparisons show

In three adult trials (median exposure 77 weeks; 85% had established atherosclerotic cardiovascular disease), injection reactions occurred in 8% versus 2% with placebo, joint pain in 5% versus 4%, and bronchitis in 4% versus 3%.

Medicine- and study-specific examples; not a safety ranking.

Sources

Leqvio prescribing information

04Absorb less cholesterol

Ezetimibe

Cholesterol absorption inhibition · Ezetimibe

The normal pathway

The small intestine absorbs cholesterol from food and bile through a transporter called NPC1L1.

What the medicine changes

Ezetimibe inhibits NPC1L1, reducing cholesterol delivered to the liver. The liver responds by increasing LDL receptors and drawing more LDL from blood.

It acts at a different step from statins and is also used in combinations. It is not a general fat-absorption blocker.

Explore therapiesEzetimibe Ezetimibe + simvastatin Bempedoic acid + ezetimibe

Commonly reported effects

Diarrhea, joint aches, fatigue and respiratory symptoms were reported; differences from placebo were generally small.

Why they may happen

Its intestinal action might suggest a link to digestive symptoms, but the label does not establish how it causes diarrhea. The reasons for aches and respiratory symptoms are also uncertain.

Other important risks

Liver-enzyme elevations, muscle injury and allergic reactions can occur. Combination treatment has its own risks; most reported rhabdomyolysis cases involved a statin or another medicine associated with muscle injury.

What placebo comparisons show

In ten monotherapy trials for primary hyperlipidemia (ages 9–86; median exposure 12 weeks), diarrhea occurred in 4.1% versus 3.7% with placebo, and joint pain in 3.0% versus 2.2%. These figures do not describe ezetimibe–statin combination treatment.

Medicine- and study-specific examples; not a safety ranking.

Sources

Zetia prescribing information

05Make less cholesterol

Bempedoic acid

ATP-citrate lyase inhibition · Bempedoic acid

The normal pathway

ATP-citrate lyase supplies material for cholesterol synthesis at a step before HMG-CoA reductase, the statin target.

What the medicine changes

Bempedoic acid is activated mainly in the liver and inhibits ACL. The fall in liver cholesterol increases LDL receptors and LDL clearance from blood.

Its activating enzyme is absent from skeletal muscle in mechanistic studies. This helps explain its different tissue activity, but does not mean muscle symptoms cannot occur.

Explore therapiesBempedoic acid Bempedoic acid + ezetimibe

Commonly reported effects

Raised uric acid, sometimes with gout, is a notable effect. Muscle spasms, abdominal discomfort and changes in liver or kidney-related blood tests are also reported.

Why they may happen

Inhibition of a kidney transporter called OAT2 is thought to explain small increases in uric acid and creatinine. Higher uric acid can trigger gout. A creatinine rise alone does not establish kidney injury; other reported effects have less certain explanations.

Other important risks

Tendon injury or rupture is an important labeled warning, particularly with prior tendon problems or other risk factors. It belongs apart from the everyday-symptom list.

What placebo comparisons show

The label’s cardiovascular-outcomes trial data report raised uric acid (hyperuricemia) in 16% versus 8% with placebo, gout in 3.2% versus 2.2%, and tendon rupture in 1.2% versus 0.9% (median exposure 3.1 years). Participants had cardiovascular disease or high risk and could not or would not take recommended statin doses because of adverse effects.

Medicine- and study-specific examples; not a safety ranking.

Sources

Nexletol prescribing information Bempedoic acid tissue activation study (2016) CLEAR Outcomes primary publication (2023)

Mechanism, marker, outcome

How a drug works explains its biological target. LDL-C measures cholesterol carried in LDL; ApoB helps reflect the number of atherogenic particles. Trials answer a separate question: whether treatment reduces heart attacks, strokes or deaths in the people studied. A shared pathway does not guarantee equal benefit or safety.

Compare lipid lowering Explore cardiovascular outcomes

A primer on selected LDL-lowering medicines. Blood-pressure drugs, blood thinners and heart-failure medicines work through other pathways and are outside this page’s scope.