Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ATROMID-S vs NIACOR
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Inhibits hepatic triglyceride synthesis and increases lipoprotein lipase activity, leading to reduced VLDL and triglycerides.
Niacin (nicotinic acid) reduces VLDL and LDL synthesis by inhibiting lipolysis in adipose tissue, decreasing free fatty acid flux to the liver, and inhibiting hepatic triglyceride synthesis. It also increases HDL by reducing catabolism of apolipoprotein A-I.
Type III hyperlipoproteinemia,Hypertriglyceridemia (Fredrickson types IV and V) not responsive to diet
Adjunct to diet for reduction of elevated total cholesterol, LDL-C, apo B, and triglyceride levels, and to increase HDL-C in primary hypercholesterolemia and mixed dyslipidemia,Adjunct to diet for reduction of risk of recurrent myocardial infarction in patients with coronary artery disease and hypercholesterolemia,Adjunct to diet for slowing progression of coronary atherosclerosis,Off-label: treatment of pellagra (niacin deficiency)
500 mg to 1 g orally twice daily. Maximum dose 2 g/day.
Initial: 250 mg orally once daily after evening meal; titrate up by 250–500 mg/day every 2–4 weeks. Maintenance: 1–2 g/day in divided doses (2–3 times daily). Maximum: 6 g/day.
Terminal elimination half-life is 6-8 hours in patients with normal renal function; may be prolonged to 12-24 hours in renal impairment.
20–45 minutes for immediate-release niacin; terminal half-life of main metabolites (nicotinuric acid) is approximately 1.5–4 hours; short half-life necessitates multiple daily dosing for lipid effects
Hepatic via glucuronidation and oxidation; major metabolite is clofibric acid.
Hepatic metabolism via two pathways: conjugation with glycine to form nicotinuric acid (major, low-affinity high-capacity) and oxidation to N-methylnicotinamide and other metabolites (minor, high-affinity low-capacity). Enzymes involved: nicotinamide N-methyltransferase (NNMT) and aldehyde oxidase.
Primarily renal excretion as glucuronide conjugates; approximately 60-70% of the dose is excreted in urine, 20-30% in feces via biliary elimination.
Renal: 60-88% as unchanged drug and metabolites after oral administration; fecal: <2%
>95% bound to plasma proteins, primarily albumin.
<20% bound to albumin; minimal binding to other plasma proteins
0.11-0.14 L/kg; low Vd indicates limited extravascular distribution, consistent with high protein binding.
0.5–0.7 L/kg; indicates distribution into total body water and some tissue binding
Oral: approximately 60-70% due to first-pass metabolism; administered as clofibrate (prodrug) which is hydrolyzed to active clofibric acid.
Oral immediate-release: 60–76% (variable due to first-pass metabolism); sustained-release: lower bioavailability (50–60%) due to increased presystemic metabolism
GFR 30-59 m L/min: 500 mg twice daily. GFR 15-29 m L/min: 250 mg twice daily. GFR <15 m L/min: avoid use.
No specific adjustment recommended; use caution in severe renal impairment (Cr Cl <30 m L/min) due to potential accumulation; consider reducing dose or prolonging interval.
Child-Pugh Class B or C: avoid use or reduce dose by at least 50%; not recommended in severe hepatic impairment.
Contraindicated in Child-Pugh class B and C; use with caution in mild impairment (Child-Pugh A) with dose reduction of 50% initially.
Not recommended; safety and efficacy not established in pediatric patients.
For hyperlipidemia (off-label): Initial 50–100 mg/kg/day orally divided into 2–3 doses; titrate over 4–6 weeks up to 200–300 mg/kg/day; maximum 6 g/day. Not recommended in children <2 years.
Start at lower end of dosing range (500 mg twice daily). Monitor renal function; adjust dose based on GFR.
Start at lowest dose (250 mg daily); titrate slowly due to increased risk of flushing, hypotension, and hepatotoxicity; monitor liver function and glucose closely.
None
None.
Hepatotoxicity,Cholelithiasis,Renal impairment dose adjustment,Rhabdomyolysis risk with statins,Malignancy risk (hepatic, GI)
Hepatotoxicity: elevated liver enzymes, hepatitis; discontinue if persistent elevations occur,Flushing: prostaglandin-mediated, can be reduced by taking aspirin prior; tolerance develops,Hyperuricemia: may precipitate gout,Hyperglycemia: may increase blood glucose; use with caution in diabetes,Peptic ulcer disease: reactivation may occur,Hypotension: can occur, especially with vasoactive drugs
Hypersensitivity to clofibrate,Active liver disease,Severe renal dysfunction,Primary biliary cirrhosis,Pregnancy
Hypersensitivity to niacin or any component of formulation,Significant or unexplained hepatic dysfunction,Active peptic ulcer disease,Arterial hemorrhage
High-fat meals may reduce absorption; consistent timing of administration with food is recommended. Grapefruit juice may increase drug levels; avoid excessive intake. Alcohol may exacerbate hepatotoxicity.
Avoid high-fat meals as they may increase risk of flushing. Take with low-fat snack. Alcohol and hot drinks can exacerbate flushing.
FDA Pregnancy Category C. First trimester: Potential for teratogenicity based on animal studies showing skeletal and visceral anomalies. Human data limited; use only if benefit outweighs risk. Second and third trimesters: May cause fetal harm due to placental transfer and potential for reduced fetal growth.
FDA Pregnancy Category C. Niacin is not recommended for use in pregnant women due to potential fetal harm, though no well-controlled studies exist. In animal studies, high doses have caused fetal abnormalities. First trimester: Avoid use due to theoretical risk of teratogenicity. Second and third trimesters: Use only if clearly needed, as niacin can cause vasodilation and potential hypotension, which may reduce uteroplacental perfusion.
Excreted into breast milk in low amounts; M/P ratio not established. Due to potential for serious adverse effects in infants, a decision should be made to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.
Niacin is excreted into human breast milk in minimal amounts; M/P ratio unknown. The American Academy of Pediatrics considers niacin compatible with breastfeeding. However, high maternal doses may lead to adverse effects in the infant due to potential accumulation. Caution is advised; monitor infant for flushing or gastrointestinal disturbances.
No specific dosing adjustments recommended due to lack of data. However, pharmacokinetic changes in pregnancy (increased volume of distribution, altered metabolism) may necessitate careful monitoring and empiric dose adjustments based on clinical response and adverse effects.
No specific dose adjustments recommended due to lack of pharmacokinetic studies in pregnant women. However, physiological changes in pregnancy (increased plasma volume, renal clearance) may reduce niacin levels, potentially requiring dose increase. Use the lowest effective dose and avoid extended-release formulations due to higher hepatotoxicity risk. Usual adult doses (500-2000 mg/day) may be used with caution.
ATROMID-S (clofibrate) is a fibric acid derivative primarily indicated for hyperlipidemia but its use is now limited due to increased non-cardiovascular mortality and cholelithiasis risk. Monitor liver function and prothrombin time (potentiates warfarin). Not first-line; consider statins or fibrates like fenofibrate.
Niacor (niacin) can cause profound flushing, which may be mitigated by taking aspirin 30 minutes prior or using extended-release formulations. Monitor liver function and blood glucose, as niacin can elevate transaminases and worsen glycemic control. Patients with gout may experience increased uric acid levels.
Take with meals to reduce gastrointestinal upset.,Report unexplained muscle pain, tenderness, or weakness; may indicate myopathy.,Avoid alcohol as it may increase liver enzyme elevations.,Notify your doctor if you develop gallstones symptoms (e.g., right upper abdominal pain, nausea).,Use effective contraception as clofibrate may cause fetal harm.
Take with food to reduce stomach upset.,Do not crush or chew extended-release tablets.,Flushing is common and may decrease with continued use.,Avoid alcohol and hot beverages near dosing time to reduce flushing.,Report unexplained muscle pain, tenderness, or weakness.,Monitor blood sugar if diabetic.,Do not substitute with dietary supplements without doctor approval.
No interactions on record
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ATROMID-S vs NIACOR, answered by our medical review team.
ATROMID-S is a Antilipemic Agent that works by Inhibits hepatic triglyceride synthesis and increases lipoprotein lipase activity, leading to reduced VLDL and triglycerides.. NIACOR is a Antilipemic agent that works by Niacin (nicotinic acid) reduces VLDL and LDL synthesis by inhibiting lipolysis in adipose tissue, decreasing free fatty acid flux to the liver, and inhibiting hepatic triglyceride synthesis. It also increases HDL by reducing catabolism of apolipoprotein A-I.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ATROMID-S and NIACOR depend on the specific clinical indication. These are agents from distinct pharmacological classes and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of ATROMID-S is: 500 mg to 1 g orally twice daily. Maximum dose 2 g/day.. The standard adult dose of NIACOR is: Initial: 250 mg orally once daily after evening meal; titrate up by 250–500 mg/day every 2–4 weeks. Maintenance: 1–2 g/day in divided doses (2–3 times daily). Maximum: 6 g/day.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between ATROMID-S and NIACOR in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. ATROMID-S is classified as Category C. FDA Pregnancy Category C. First trimester: Potential for teratogenicity based on animal studies showing skeletal and visceral anomalies. Human data limited; use only if benefit out. NIACOR is classified as Category C. FDA Pregnancy Category C. Niacin is not recommended for use in pregnant women due to potential fetal harm, though no well-controlled studies exist. In animal studies, high doses ha. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.