NIACIN
Clinical safety rating: safe
Animal studies have demonstrated safety
Niacin (nicotinic acid) inhibits hepatic diacylglycerol acyltransferase-2 (DGAT2), decreasing triglyceride synthesis; it also reduces VLDL secretion and increases HDL by reducing hepatic lipase activity.
| Metabolism | Hepatic metabolism via two pathways: conjugation with glycine to form nicotinuric acid (major, low-affinity) and conversion to nicotinamide via amidases. Saturable metabolism leads to dose-dependent pharmacokinetics. |
| Excretion | Renal excretion of unchanged drug and metabolites accounts for approximately 60-88% of the administered dose after oral administration. Fecal elimination is minimal, representing less than 10%. |
| Half-life | The terminal elimination half-life of nicotinic acid is approximately 20-45 minutes; however, for the extended-release formulation, the half-life is prolonged to 2-6 hours due to slower absorption. |
| Protein binding | Niacin is less than 20% bound to plasma proteins. Its primary metabolite, nicotinuric acid, is approximately 60-70% bound. |
| Volume of Distribution | The apparent volume of distribution is reported to be 0.5-1.0 L/kg. This moderate volume indicates distribution into total body water. |
| Bioavailability | Oral bioavailability of immediate-release niacin is approximately 100% at low doses but decreases with higher doses due to saturable metabolism. Extended-release formulations have bioavailability of 60-90% relative to immediate-release. |
| Onset of Action | For immediate-release niacin, vasodilation and flushing occur within 15-30 minutes of oral administration. For extended-release, onset is delayed to 1-2 hours. Lipid effects may take days to weeks. |
| Duration of Action | For immediate-release niacin, the flushing effect lasts 30-60 minutes; lipid effects persist for several hours. Extended-release formulations provide lipid effects for up to 24 hours, allowing once-daily dosing. |
| Action Class | Aminoglycosides |
| Brand Substitutes | Acil 500mg Injection, Emica 500mg Injection, Mika Best 500mg Injection, Ivimicin 500mg Injection, Mikaject 500mg Injection, Mkcin 100mg Injection, Megamika 100mg Injection, Mikabit 100mg Injection, Amicid 100mg Injection, Ivimicin 100mg Injection, Cachmik 250mg Injection, Amibiotic 250mg Injection, Amister 250mg Injection, Ivimicin 250mg Injection, Emica 250mg Injection |
Initial: 250-500 mg orally once daily at bedtime; titrate gradually to maintenance dose of 1-2 g/day orally in divided doses (typically 2-3 times daily). Maximum dose: 6 g/day.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for GFR ≥30 mL/min. For GFR <30 mL/min, caution is advised; consider reducing dose by 50% and monitor for adverse effects. |
| Liver impairment | Contraindicated in Child-Pugh class C (severe hepatic impairment). For Child-Pugh class A or B, dose reduction of 50% and close monitoring of liver function tests are recommended. |
| Pediatric use | For dyslipidemia: 100-250 mg orally once daily at bedtime; titrate as tolerated to maximum of 2 g/day or 30 mg/kg/day, whichever is lower. For pellagra: 50-100 mg orally 3 times daily. |
| Geriatric use | Start at low end of dosing range (250 mg once daily) and titrate slowly. Monitor for hypotension, flushing, and hepatotoxicity; consider extended-release formulation to improve tolerability. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Statins may increase risk of myopathy Can cause profound flushing and hepatotoxicity.
| Breastfeeding | Niacin is excreted into human breast milk with an average M/P ratio of 0.8 (range 0.5-1.0). At recommended dietary allowances (RDA) doses, it is considered compatible with breastfeeding. Pharmacologic doses (≥500 mg/day) may cause adverse effects in the infant (e.g., flushing, hepatotoxicity); monitor infant for signs of toxicity. Use with caution and consider risk-benefit analysis. |
| Teratogenic Risk | FDA Pregnancy Category A (dietary reference intake doses); Category C (pharmacologic doses). No evidence of teratogenicity in human studies; high doses may be associated with fetal hypoglycemia and hyperuricemia. First trimester: no known risk. Second and third trimesters: no known fetal adverse effects at recommended doses; high doses may cause maternal hepatic toxicity and potentially affect fetal metabolism. |
■ FDA Black Box Warning
None
| Serious Effects |
["Active liver disease or unexplained elevated transaminases","Active peptic ulcer disease","Arterial bleeding","Hypersensitivity to niacin or any component"]
| Precautions | ["Hepatotoxicity (elevated liver enzymes, rare fulminant hepatitis)","Flushing (prostaglandin-mediated, can be reduced by aspirin or extended-release formulations)","Hyperuricemia (may precipitate gout)","Hyperglycemia (may worsen glycemic control in diabetes)","Gastrointestinal distress (nausea, dyspepsia)","Acute hypotension (with rapid dose titration or concomitant vasodilators)"] |
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| Fetal Monitoring | Monitor maternal liver function tests (ALT, AST) and serum glucose levels every 4-6 weeks during pregnancy, especially with doses >500 mg/day. Assess fetal growth via ultrasound every trimester if using pharmacologic doses. Monitor for maternal flushing, hyperglycemia, and uric acid levels. For pharmacologic doses, consider fetal echocardiography if maternal liver toxicity develops. |
| Fertility Effects | No adverse effects on fertility in animal studies. In humans, no impairment of fertility reported at therapeutic doses. Niacin does not affect ovulation, sperm production, or implantation. Indirect effects through improvement of lipid profiles may be beneficial for fertility in women with polycystic ovary syndrome. |