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[Pharmacology](https://durgical.com/en/pharmacology/) · [Nicotinic acid and derivatives](https://durgical.com/en/pharmacology/classes/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](https://durgical.com/en/pharmacology/classes/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](https://www.rcsb.org/structure/8K5B) · Drag to rotate · pinch to zoom

## 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 →](https://durgical.com/en/conditions/atherosclerosis-and-dyslipidaemia/)
- Very high triglycerides with risk of pancreatitis, as an adjunct [Familial hypertriglyceridaemia →](https://durgical.com/en/conditions/familial-hypertriglyceridaemia/)
- Pellagra (niacin deficiency), at vitamin doses [Pellagra (niacin deficiency) →](https://durgical.com/en/conditions/pellagra/)

## Adverse effects

### Common

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

### Serious (rare, important)

- Hepatotoxicity, severe when sustained-release replaces immediate-release at the same dose
- Myopathy, especially with a statin
- Gout attacks; worsening of peptic ulcer
- Small falls in platelets and rise in prothrombin time

## 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.

## Memory aid

Niacin's «4 H»: Hot flushes, Hyperglycemia, Hyperuricemia, Hepatotoxicity. Aspirin before the dose cools the flush.

## 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.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/nicotinic-acid/)

## Related drugs

- [Fenofibrate](https://durgical.com/en/pharmacology/fenofibrate/)
- [Rosuvastatin](https://durgical.com/en/pharmacology/rosuvastatin/)
- [Colestyramine](https://durgical.com/en/pharmacology/colestyramine/)

## Related conditions

- [Atherosclerosis and dyslipidaemia](https://durgical.com/en/conditions/atherosclerosis-and-dyslipidaemia/)
- [Familial hypertriglyceridaemia](https://durgical.com/en/conditions/familial-hypertriglyceridaemia/)
- [Pellagra (niacin deficiency)](https://durgical.com/en/conditions/pellagra/)

[← Back to the class: Nicotinic acid and derivatives](https://durgical.com/en/pharmacology/classes/nicotinic-acid-and-derivatives/)

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](https://medlineplus.gov/druginfo/meds/a682518.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [DailyMed - NIACIN tablet, extended release](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6e604319-e164-4056-ab80-b78b98c519c7) (DailyMed (U.S. National Library of Medicine), 2026); [Cryo-EM structure of niacin bound human hydroxy-carboxylic acid receptor 2 (Local refinement)](https://www.rcsb.org/structure/8K5B) (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.

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