Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
CEFACLOR vs ACEPHEN
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Bactericidal; inhibits cell wall synthesis by binding to penicillin-binding proteins (PBPs), disrupting peptidoglycan cross-linking.
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.
Acute otitis media,Acute exacerbations of chronic bronchitis,Pharyngitis/tonsillitis,Uncomplicated skin and skin structure infections,Urinary tract infections,Lower respiratory tract infections including pneumonia
Mild to moderate pain,Fever
250-500 mg orally every 8 hours
325-650 mg orally every 4-6 hours as needed; maximum 4 g/day.
Terminal elimination half-life: 0.5-1 hour; prolonged to 2-3 hours in renal impairment
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.
Hepatic (minor); primarily renally excreted unchanged.
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: 60-85% unchanged in urine within 8 hours; biliary/fecal: minor, ~5%
Renal: 90-95% as unchanged drug; tubular secretion and glomerular filtration. Biliary/fecal: <5%.
25-50% bound to plasma proteins, primarily albumin
Approximately 10-20% bound to serum albumin; extensive tissue binding.
0.35-0.5 L/kg; distributes into most body tissues and fluids, including middle ear, sinus, and respiratory secretions
Apparent Vd: 0.5-0.7 L/kg (30-40 L in a 70 kg adult). Distributions into CSF and breast milk.
Oral: 95% well absorbed; food does not significantly affect absorption
Oral: 85-90% (first-pass metabolism minimal). Rectal: approximately 70-80% of oral bioavailability.
Cr Cl 10-50 m L/min: 50% of usual dose every 8 hours; Cr Cl <10 m L/min: 50% of usual dose every 12 hours
GFR 10-50 m L/min: 650 mg every 6 hours; GFR <10 m L/min: 650 mg every 8 hours.
No adjustment required for mild to moderate hepatic impairment; safety in severe impairment not established
Child-Pugh Class A: no adjustment; Child-Pugh Class B: maximum 2 g/day; Child-Pugh Class C: maximum 1 g/day.
20-40 mg/kg/day orally divided every 8 hours; maximum 1 g/day
10-15 mg/kg/dose orally every 4-6 hours; maximum 75 mg/kg/day or 4 g/day, whichever is less.
No specific adjustment, but monitor renal function; initiate at lower end of dosing range due to age-related renal decline
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.
Hypersensitivity reactions, including anaphylaxis,Clostridium difficile-associated diarrhea,Seizures (especially with renal impairment),Prolonged PT in patients on anticoagulants,False-positive urine glucose test
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.
Known hypersensitivity to cephalosporins or any component,Previous immediate hypersensitivity reaction to penicillins (cross-sensitivity)
Hypersensitivity to acetaminophen or any component of the formulation; severe hepatic impairment or active liver disease.
No significant food interactions; cefaclor can be taken with or without food.,Absorption may be slightly delayed with food but total bioavailability is unaffected.,Avoid grapefruit juice? No known interaction.,Alcohol: No specific interaction, but caution as it may increase side effects like gastrointestinal upset.
Alcohol: increased risk of hepatotoxicity. Avoid concurrent use. Food: no significant interaction, but taking with food may reduce minor gastrointestinal irritation.
First trimester: No increased risk of major congenital malformations based on limited human data; animal studies show no teratogenicity at clinically relevant doses. Second/third trimester: No known fetal risks; Cefaclor crosses the placenta with fetal serum concentrations approximately 10-20% of maternal levels.
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.
Cefaclor is excreted into human breast milk in low concentrations (M/P ratio approximately 0.05-0.10). Considered compatible with breastfeeding by the American Academy of Pediatrics; use with caution in nursing infants with potential for diarrhea or allergic sensitization.
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).
No dose adjustment required in pregnancy; pharmacokinetic changes (increased volume of distribution, renal clearance) do not necessitate dose modification due to wide therapeutic index.
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.
Cefaclor is a second-generation cephalosporin with activity against both Gram-positive and Gram-negative organisms, but not Pseudomonas or MRSA.,It is stable against some beta-lactamases, but resistance can occur via extended-spectrum beta-lactamases (ESBLs).,Dose adjustment is required in renal impairment (Cr Cl <40 m L/min).,It is available as an oral suspension and capsules; suspension must be refrigerated and shaken well before use.,Cefaclor may cause a serum sickness-like reaction, especially in children, characterized by rash, arthralgia, and fever.,It has a short half-life (0.6-0.9 hours) and is usually dosed every 8 hours.,Avoid use in patients with immediate hypersensitivity to penicillins due to cross-reactivity risk (about 10%).
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 this medication exactly as prescribed, usually every 8 hours, with or without food.,Complete the full course of therapy even if you feel better to prevent bacterial resistance.,Shake the oral suspension well before each dose and refrigerate it; discard any unused portion after 14 days.,Contact your healthcare provider if you develop severe diarrhea, rash, joint pain, or fever.,Inform your doctor if you have a history of allergic reactions to penicillins or cephalosporins.,Do not take this medication if you are allergic to cefaclor or any other cephalosporin antibiotic.,If a dose is missed, take it as soon as remembered unless it is almost time for the next dose; do not double the dose.
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.
"Phenindione, a vitamin K antagonist anticoagulant, potentiates the effect of cefaclor, a second-generation cephalosporin antibiotic. Cefaclor may reduce vitamin K production by suppressing intestinal flora, thereby enhancing the anticoagulant effect of phenindione. This interaction can lead to an increased international normalized ratio (INR) and risk of bleeding, particularly in patients with poor nutritional status or prolonged antibiotic therapy."
"Dicoumarol may increase the anticoagulant activities of Cefaclor."
"Warfarin may increase the anticoagulant activities of Cefaclor."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about CEFACLOR vs ACEPHEN, answered by our medical review team.
CEFACLOR is a Cephalosporin Antibiotic that works by Bactericidal; inhibits cell wall synthesis by binding to penicillin-binding proteins (PBPs), disrupting peptidoglycan cross-linking.. 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 CEFACLOR 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 CEFACLOR is: 250-500 mg orally every 8 hours. 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 CEFACLOR 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. CEFACLOR is classified as Category A/B. First trimester: No increased risk of major congenital malformations based on limited human data; animal studies show no teratogenicity at clinically relevant doses. Second/third t. 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.