Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
OMACOR vs ATROMID-S
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Omega-3-acid ethyl esters (EPA and DHA) reduce hepatic triglyceride synthesis by inhibiting acyl-Co A:1,2-diacylglycerol acyltransferase and increasing beta-oxidation. They also decrease very-low-density lipoprotein (VLDL) secretion and enhance triglyceride clearance from circulating VLDL particles.
Inhibits hepatic triglyceride synthesis and increases lipoprotein lipase activity, leading to reduced VLDL and triglycerides.
FDA: Adjunct to diet for reduction of triglyceride levels in adult patients with severe hypertriglyceridemia (≥500 mg/d L).,Off-label: Secondary prevention of cardiovascular events in patients with hypertriglyceridemia or high cardiovascular risk.
Type III hyperlipoproteinemia,Hypertriglyceridemia (Fredrickson types IV and V) not responsive to diet
4 g orally once daily or 2 g orally twice daily, taken with meals. Each capsule contains 1 g of omega-3-acid ethyl esters (approximately 465 mg eicosapentaenoic acid and 375 mg docosahexaenoic acid).
500 mg to 1 g orally twice daily. Maximum dose 2 g/day.
Terminal elimination half-life: ~55–75 hours for EPA and DHA (beta-phase). Clinical context: steady-state achieved after 4–8 weeks; half-life supports once-daily dosing.
Terminal elimination half-life is 6-8 hours in patients with normal renal function; may be prolonged to 12-24 hours in renal impairment.
Omega-3-acid ethyl esters are primarily hydrolyzed by pancreatic lipase to free fatty acids (EPA and DHA), which are then absorbed and incorporated into chylomicrons. They undergo hepatic metabolism via beta-oxidation. CYP450 involvement is minimal.
Hepatic via glucuronidation and oxidation; major metabolite is clofibric acid.
Primarily fecal as unchanged drug and metabolites; <5% renal. Biliary excretion accounts for ~90% of elimination via feces, with minimal urinary excretion (0.5–2%).
Primarily renal excretion as glucuronide conjugates; approximately 60-70% of the dose is excreted in urine, 20-30% in feces via biliary elimination.
Highly protein-bound (>99%) primarily to albumin.
>95% bound to plasma proteins, primarily albumin.
Vd: ~0.2–0.3 L/kg (EPA), ~2–3 L/kg (DHA). Clinical meaning: extensive tissue distribution, especially in adipose and cardiac tissues.
0.11-0.14 L/kg; low Vd indicates limited extravascular distribution, consistent with high protein binding.
Oral: 50–100% (enhanced with fatty meal; absolute bioavailability not determined).
Oral: approximately 60-70% due to first-pass metabolism; administered as clofibrate (prodrug) which is hydrolyzed to active clofibric acid.
No dose adjustment required for any degree of renal impairment. Use caution in patients with renal disease due to potential for increased bleeding risk.
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.
Contraindicated in patients with Child-Pugh class C (severe) hepatic impairment. For Child-Pugh A or B, no dose adjustment is recommended, but monitor liver function tests periodically.
Child-Pugh Class B or C: avoid use or reduce dose by at least 50%; not recommended in severe hepatic impairment.
Safety and efficacy not established in pediatric patients. Not recommended for use in children.
Not recommended; safety and efficacy not established in pediatric patients.
No specific dose adjustment recommended. Monitor for potential drug interactions, especially with anticoagulants, due to increased bleeding risk. Start at lower end of dosing range if elderly patient has significant comorbidity or polypharmacy.
Start at lower end of dosing range (500 mg twice daily). Monitor renal function; adjust dose based on GFR.
No FDA black box warning.
None
Increased bleeding risk (monitor patients on anticoagulants).,Atrial fibrillation in patients with prior history or at high risk.,Persistent elevations of ALT or AST, especially with other hepatotoxic drugs.,Hypersensitivity reactions including anaphylaxis.,Fish allergy (capsules contain fish oil).
Hepatotoxicity,Cholelithiasis,Renal impairment dose adjustment,Rhabdomyolysis risk with statins,Malignancy risk (hepatic, GI)
Hypersensitivity to omega-3-acid ethyl esters or any component.,Acute pancreatitis with marked hypertriglyceridemia (consider if triglycerides >500 mg/d L and chylomicronemia).
Hypersensitivity to clofibrate,Active liver disease,Severe renal dysfunction,Primary biliary cirrhosis,Pregnancy
Avoid high-fat meals as they may increase triglyceride levels. No specific food interactions known, but consistency in timing with meals is recommended.
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.
FDA Pregnancy Category C. No evidence of teratogenicity in animal studies at doses up to 10 times the human dose. There are no adequate and well-controlled studies in pregnant women. Use only if potential benefit justifies potential risk to fetus. Omega-3-acid ethyl esters may inhibit prostaglandin synthesis and delay labor. Third trimester use may increase risk of bleeding in mother and neonate.
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.
Not recommended during breastfeeding. Omega-3 fatty acids are excreted in human milk; M/P ratio not established. Potential for adverse effects in nursing infant. Consider alternative treatment or discontinue nursing.
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.
No specific dose adjustments recommended for pregnancy-induced pharmacokinetic changes. Use with caution as pregnancy may alter lipid profiles; monitor triglyceride levels and adjust dose accordingly.
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.
Omacor (omega-3-acid ethyl esters) is indicated as an adjunct to diet for severe hypertriglyceridemia (≥500 mg/d L). Monitor LDL-C levels as they may increase during therapy; adjust statin dose if needed. Administer with meals to enhance absorption and reduce gastrointestinal side effects. Avoid use in patients with fish or shellfish allergy. May prolong bleeding time; monitor in patients on anticoagulants.
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.
Take with food to improve absorption and reduce burping or fishy taste.,Do not take if you have an allergy to fish or shellfish.,Report unusual bleeding or bruising, especially if you are on blood thinners.,Do not substitute with over-the-counter fish oil supplements as they are not equivalent.,Continue dietary modifications and exercise as part of your treatment plan.
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.
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 OMACOR vs ATROMID-S, answered by our medical review team.
OMACOR is a Antilipemic that works by Omega-3-acid ethyl esters (EPA and DHA) reduce hepatic triglyceride synthesis by inhibiting acyl-Co A:1,2-diacylglycerol acyltransferase and increasing beta-oxidation. They also decrease very-low-density lipoprotein (VLDL) secretion and enhance triglyceride clearance from circulating VLDL particles.. ATROMID-S is a Antilipemic Agent that works by Inhibits hepatic triglyceride synthesis and increases lipoprotein lipase activity, leading to reduced VLDL and triglycerides.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between OMACOR and ATROMID-S 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 OMACOR is: 4 g orally once daily or 2 g orally twice daily, taken with meals. Each capsule contains 1 g of omega-3-acid ethyl esters (approximately 465 mg eicosapentaenoic acid and 375 mg docosahexaenoic acid).. The standard adult dose of ATROMID-S is: 500 mg to 1 g orally twice daily. Maximum dose 2 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 OMACOR and ATROMID-S 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. OMACOR is classified as Category C. FDA Pregnancy Category C. No evidence of teratogenicity in animal studies at doses up to 10 times the human dose. There are no adequate and well-controlled studies in pregnant wome. 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. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.