Pharmacology · Nicotinic acid and derivatives

Nicotinic acid (niacin) !

Vitamin B3 used at high doses to lower triglycerides and LDL and raise HDL. Flushing, high glucose and liver effects limit it.

Updated 2026-11-01

Class: Nicotinic acid and derivatives
Receptor: Niacin receptor HCA2 (GPR109A)
ATC code: C10AD02

Also called: niacin, vitamin B3

Niacin receptor HCA2 (GPR109A)Nicotinic acid (niacin)

The figure shows nicotinic acid bound to human HCA2 (cryo-EM, receptor region after local refinement).

Target in 3D: Niacin receptor HCA2 (GPR109A). PDB structure 8K5B (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

In adipose tissue, niacin acts on the Gi-coupled receptor HCA2 (GPR109A), lowering cAMP and the activity of hormone-sensitive lipase; fewer fatty acids reach the liver. In the liver it inhibits fatty acid synthesis and esterification, so less triglyceride is made, apo B is degraded and less VLDL (and later LDL) is released. It also raises HDL and increases lipoprotein lipase activity. Prostaglandins released through the same receptor in skin cause flushing.

Activates HCA2 (Gi) on fat cells: less lipolysis
Fewer fatty acids reach the liver
Liver makes less triglyceride and VLDL
Triglycerides and LDL fall; HDL rises

Pharmacokinetics

Absorption: Oral; immediate-release niacin is almost completely and rapidly absorbed.
Metabolism: Rapid metabolism in the liver.
Elimination: By the kidneys, as metabolites.
Half-life: Short for the immediate-release form (well under an hour), which is why extended-release forms exist.

Indications

Dyslipidemia with high triglycerides or LDL when other drugs are not suitable Atherosclerosis and dyslipidaemia →
Very high triglycerides with risk of pancreatitis, as an adjunct Familial hypertriglyceridaemia →
Pellagra (niacin deficiency), at vitamin doses Pellagra (niacin deficiency) →

Adverse effects

Common

Flushing, warmth and itching of the face and upper body
Dyspepsia, nausea, diarrhea
Rise in fasting glucose
Rise in uric acid

Contraindications

Active liver disease or unexplained persistent transaminase rises
Active peptic ulcer disease
Arterial bleeding
Hypersensitivity to niacin

Key interactions

Statins: Add to the risk of myopathy and rhabdomyolysis.
Bile acid sequestrants: Bind niacin; 4 to 6 hours or more are left between them.
Aspirin: Reduces flushing; it may also lower the clearance of nicotinic acid (clinical relevance unclear).
Insulin and other antidiabetic drugs: Niacin raises glucose, so antidiabetic needs may increase.
Antihypertensives and other vasoactive drugs: Niacin can add to their effect and cause postural hypotension.

What is monitored

Liver enzymes before and during treatment
Fasting glucose, especially in diabetes
Uric acid
Lipid panel; phosphorus and platelets when relevant

Administration and safety

The extended-release tablet is usually taken at bedtime after a low-fat snack and swallowed whole, never split, crushed or chewed.
Immediate-release and extended-release products are not interchangeable at the same dose.
Alcohol, hot drinks and spicy food around the dose worsen flushing.
Niacin is also sold as a supplement: the prescribed product is checked, not a non-prescription substitute.

Nursing care

Before: liver enzymes, glucose, uric acid, history of gout, ulcer or bleeding.
Warn that flushing is expected and usually lessens after some weeks; teach the aspirin plan if prescribed.
Ask about dizziness on standing, muscle pain, dark urine or jaundice.
In diabetes, check glucose more often after starting.

Pregnancy and breastfeeding

Stopped when pregnancy is recognized if used for lipids; breastfeeding is not recommended during treatment.

Test yourself

Think of the answer, then tap the question to see it.

Through which receptor does niacin reduce lipolysis in fat tissue?

HCA2 (GPR109A), a Gi-coupled receptor that lowers cAMP and hormone-sensitive lipase activity.

Why is niacin used with caution in diabetes?

It causes insulin resistance and raises glucose; glucose is monitored more often.

What is the classic «3 D» deficiency disease treated with niacin at vitamin doses?

Pellagra: dermatitis, diarrhea and dementia.

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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: Niacin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2026); DailyMed - NIACIN tablet, extended release (DailyMed (U.S. National Library of Medicine), 2026); Cryo-EM structure of niacin bound human hydroxy-carboxylic acid receptor 2 (Local refinement) (RCSB Protein Data Bank, 2023); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 37 (McGraw Hill, 2023).

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Representative model, for educational purposes only.