Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
COZAAR vs ACEPHEN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Losartan is a selective angiotensin II receptor type 1 (AT1) antagonist. It blocks the binding of angiotensin II to AT1 receptors in vascular smooth muscle and adrenal gland, leading to vasodilation, reduced aldosterone secretion, and decreased blood pressure. It also reduces proteinuria and slows progression of renal disease by decreasing intraglomerular pressure.
ACEPHEN (acetaminophen) is a para-aminophenol derivative with analgesic and antipyretic activity. Its mechanism involves inhibition of cyclooxygenase (COX) enzymes in the central nervous system, particularly COX-2, reducing prostaglandin synthesis. It has weak peripheral COX inhibition and minimal anti-inflammatory effect.
Hypertension,Nephropathy in patients with type 2 diabetes and hypertension,Hypertension with left ventricular hypertrophy (to reduce risk of stroke)
Mild to moderate pain,Fever
50 mg orally once daily; may increase to 100 mg once daily based on blood pressure response.
325-650 mg orally every 4-6 hours as needed; maximum 4 g/day.
Plasma half-life of losartan: approximately 2 hours; active metabolite E-3174: 6–9 hours. Clinical context: once-daily dosing due to prolonged receptor blockade by metabolite
Terminal elimination half-life: 1.0-1.5 hours in adults with normal renal function. Prolonged to 2-5 hours in hepatic impairment or elderly; requires dose adjustment in severe hepatic disease.
Losartan is extensively metabolized in the liver via CYP2C9 and CYP3A4 to its active metabolite, E-3174, which is more potent than the parent drug. E-3174 is further metabolized to inactive metabolites. Both losartan and E-3174 are excreted in urine and feces.
Acetaminophen is primarily metabolized in the liver via glucuronidation (UGT1A1, UGT1A6, UGT1A9) and sulfation (SULT1A1, SULT1A3). A minor fraction is oxidized by cytochrome P450 enzymes (CYP2E1, CYP1A2, CYP3A4) to a reactive toxic metabolite (NAPQI), which is normally detoxified by conjugation with glutathione.
Renal (35% as unchanged drug and 18% as active metabolite), biliary/fecal (approximately 60% of radiolabeled dose recovered in feces)
Renal: 90-95% as unchanged drug; tubular secretion and glomerular filtration. Biliary/fecal: <5%.
≥99% (primarily albumin); losartan ≥98.7%, active metabolite ≥99.8%
Approximately 10-20% bound to serum albumin; extensive tissue binding.
Losartan: 34 L (0.47 L/kg for 70 kg adult); active metabolite: 12 L. Indicates limited extravascular distribution
Apparent Vd: 0.5-0.7 L/kg (30-40 L in a 70 kg adult). Distributions into CSF and breast milk.
Oral: about 33% (losartan); active metabolite bioavailability not directly reported but formed via first-pass metabolism
Oral: 85-90% (first-pass metabolism minimal). Rectal: approximately 70-80% of oral bioavailability.
No dose adjustment required for GFR ≥30 m L/min; for GFR <30 m L/min, initial dose is 25 mg orally once daily.
GFR 10-50 m L/min: 650 mg every 6 hours; GFR <10 m L/min: 650 mg every 8 hours.
For Child-Pugh Class A or B: initial dose is 25 mg orally once daily; no data for Class C.
Child-Pugh Class A: no adjustment; Child-Pugh Class B: maximum 2 g/day; Child-Pugh Class C: maximum 1 g/day.
For children ≥6 years: initial dose 0.7 mg/kg (up to 50 mg) orally once daily; maximum 1.4 mg/kg (up to 100 mg) once daily.
10-15 mg/kg/dose orally every 4-6 hours; maximum 75 mg/kg/day or 4 g/day, whichever is less.
Consider lower initial dose of 25 mg orally once daily due to potential for volume depletion or decreased renal function.
Start at lowest effective dose (325 mg every 6 hours); avoid exceeding 3 g/day unless closely monitored.
None
Acetaminophen has been associated with cases of acute liver failure, at times resulting in liver transplant and death. Most of the cases of liver injury are associated with the use of acetaminophen at doses that exceed 4,000 milligrams per day, and often involve more than one acetaminophen-containing product.
Fetal toxicity (discontinue when pregnancy is detected); hypotension in volume-depleted patients; renal impairment (monitor serum creatinine and potassium); hyperkalemia; angioedema; dual blockade of renin-angiotensin system (increased risk of hypotension, hyperkalemia, renal dysfunction); hepatotoxicity; monitor for azotemia in renovascular hypertension.
Risk of severe liver injury with doses >4000 mg/day; use caution with hepatic impairment, chronic alcoholism, malnutrition, or concomitant hepatotoxic drugs; avoid exceeding recommended dose; limit use to 10 days for pain or 3 days for fever unless directed by physician; serious skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis) have occurred.
Hypersensitivity to losartan or any component; pregnancy (especially second and third trimesters); concomitant use with aliskiren in patients with diabetes mellitus or renal impairment (e GFR <60 m L/min/1.73m²); history of angioedema related to previous ARB therapy.
Hypersensitivity to acetaminophen or any component of the formulation; severe hepatic impairment or active liver disease.
No significant food interactions. However, avoid high-potassium foods (such as bananas, oranges, leafy greens, tomatoes, and avocados) in large amounts if taken with potassium supplements or if renal function is impaired. Limit salt intake as advised for hypertension management. Grapefruit juice does not interact significantly with losartan.
Alcohol: increased risk of hepatotoxicity. Avoid concurrent use. Food: no significant interaction, but taking with food may reduce minor gastrointestinal irritation.
Contraindicated in pregnancy. First trimester: Associated with congenital malformations, including renal dysplasia and oligohydramnios. Second and third trimesters: Fetal toxicity (oligohydramnios, pulmonary hypoplasia, skull ossification defects, neonatal anuria, hypotension, and death).
Pregnancy Category C. First trimester: potential risk of neural tube defects and orofacial clefts (limited human data, animal studies show embryotoxicity). Second and third trimesters: NSAID exposure associated with oligohydramnios, premature ductus arteriosus constriction, and fetal renal impairment. Avoid in third trimester.
Not recommended. No data on M/P ratio; excreted in rat milk; potential for adverse effects in nursing infant due to renin-angiotensin system blockade.
Excreted into breast milk in low concentrations (M/P ratio approximately 0.10). Considered compatible with breastfeeding; however, use lowest effective dose for shortest duration given potential for neonatal adverse effects (e.g., thrombocytopenia, renal dysfunction).
Contraindicated; no dose adjustments recommended as use should be avoided; alternative antihypertensives preferred.
No standard dose adjustments recommended; however, due to increased plasma volume and metabolism in pregnancy, higher doses may be required to achieve therapeutic effect. Avoid near term.
Cozaar (losartan) is an angiotensin II receptor blocker (ARB). Monitor renal function and electrolytes, especially potassium, within 2-4 weeks of initiation and periodically thereafter. May cause a reversible rise in serum creatinine, especially in renal artery stenosis. Has a uricosuric effect, modestly lowering uric acid levels. Avoid use in pregnancy (category D). Dose adjustment recommended for hepatic impairment. Can be used as an alternative in patients who develop ACE-inhibitor-induced cough.
ACEPHEN (acetaminophen) is commonly used for mild to moderate pain and fever. Avoid exceeding 4 g/day in adults to prevent hepatotoxicity. In patients with hepatic impairment, reduce maximum daily dose to 2 g. Consider acetylcysteine for overdose. Onset of action is 15-30 minutes orally.
Take once daily with or without food; consistency in timing is key.,Avoid potassium supplements or salt substitutes containing potassium unless directed by your doctor.,May cause dizziness, especially at start; avoid driving until you know how it affects you.,Do not use if pregnant, planning pregnancy, or breastfeeding; discuss contraception with your doctor.,Report symptoms like fainting, rapid heartbeat, or leg swelling to your doctor.,Stay well-hydrated, especially if you experience diarrhea or vomiting, as dehydration can worsen side effects.,Do not stop this medication abruptly; consult your physician before discontinuing.
Do not exceed 4000 mg (4 grams) in 24 hours.,Avoid drinking alcohol while taking this medication.,Do not combine with other products containing acetaminophen.,Take with food if stomach upset occurs.,Seek immediate medical help if you experience symptoms of liver damage: yellowing of skin/eyes, dark urine, severe abdominal pain.
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 COZAAR vs ACEPHEN, answered by our medical review team.
COZAAR is a Angiotensin Receptor Blocker that works by Losartan is a selective angiotensin II receptor type 1 (AT1) antagonist. It blocks the binding of angiotensin II to AT1 receptors in vascular smooth muscle and adrenal gland, leading to vasodilation, reduced aldosterone secretion, and decreased blood pressure. It also reduces proteinuria and slows progression of renal disease by decreasing intraglomerular pressure.. ACEPHEN is a Non-Opioid Analgesic that works by ACEPHEN (acetaminophen) is a para-aminophenol derivative with analgesic and antipyretic activity. Its mechanism involves inhibition of cyclooxygenase (COX) enzymes in the central nervous system, particularly COX-2, reducing prostaglandin synthesis. It has weak peripheral COX inhibition and minimal anti-inflammatory effect.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between COZAAR and ACEPHEN 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 COZAAR is: 50 mg orally once daily; may increase to 100 mg once daily based on blood pressure response.. The standard adult dose of ACEPHEN is: 325-650 mg orally every 4-6 hours as needed; maximum 4 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 COZAAR and ACEPHEN 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. COZAAR is classified as Category C. Contraindicated in pregnancy. First trimester: Associated with congenital malformations, including renal dysplasia and oligohydramnios. Second and third trimesters: Fetal toxicity . ACEPHEN is classified as Category C. Pregnancy Category C. First trimester: potential risk of neural tube defects and orofacial clefts (limited human data, animal studies show embryotoxicity). Second and third trimest. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.