Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ACETAMINOPHEN, ASPIRIN, AND CODEINE PHOSPHATE vs ALLEGRA-D 12 HOUR ALLERGY AND CONGESTION
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Acetaminophen: cyclooxygenase (COX) inhibitor, primarily central, analgesic and antipyretic. Aspirin: irreversible COX-1 and COX-2 inhibitor, analgesic, anti-inflammatory, antipyretic, antiplatelet. Codeine: prodrug converted to morphine; mu-opioid receptor agonist.
Fexofenadine is a selective peripheral H1-receptor antagonist; pseudoephedrine is a sympathomimetic amine that directly stimulates alpha-adrenergic receptors, causing vasoconstriction and decongestion.
Mild to moderate pain,Fever (acetaminophen and aspirin),Inflammatory conditions (aspirin)
Relief of symptoms associated with seasonal allergic rhinitis and nasal congestion in adults and children 12 years and older
1-2 tablets (each containing acetaminophen 300 mg, aspirin 300 mg, codeine phosphate 30 mg) orally every 4-6 hours as needed for pain; maximum 8 tablets/day.
Adults and children 12 years and older: 1 tablet (fexofenadine 60 mg/pseudoephedrine 120 mg) orally every 12 hours with water. Do not exceed 2 tablets in 24 hours.
Acetaminophen: 2-3 hours (terminal). Aspirin: 15-30 minutes (parent drug); salicylate: 2-3 hours at low doses, 15-30 hours at high doses due to saturable metabolism. Codeine: 2.5-4 hours. Clinical context: Prolonged half-life of salicylate at high doses increases risk of toxicity; hepatic impairment prolongs acetaminophen and codeine half-lives.
Fexofenadine: 14.4 hours in healthy adults (range 11-15 h); pseudoephedrine: 5-8 hours (p H-dependent urinary excretion may prolong to 14-16 h in alkaline urine).
Acetaminophen: hepatic via CYP2E1, CYP1A2, CYP3A4; glucuronidation and sulfation; NAPQI formation. Aspirin: hepatic hydrolysis to salicylate; conjugation with glycine and glucuronic acid. Codeine: hepatic via CYP2D6 to morphine (active); also via CYP3A4 to norcodeine.
Fexofenadine is minimally metabolized by the liver (≤5% via CYP3A4); pseudoephedrine is partially metabolized by hepatic N-demethylation and undergoes renal excretion.
Acetaminophen: renal excretion of metabolites (glucuronide and sulfate conjugates, ~85-90%), minor parent drug (<5%). Aspirin: renal excretion of salicylate and its metabolites (salicyluric acid, glucuronides, gentisic acid), dose-dependent; at therapeutic doses, ~50-80% as free salicylate and conjugates. Codeine: renal excretion of free and conjugated codeine (about 90%) and metabolites (morphine, norcodeine).
Fexofenadine: 95% excreted unchanged in feces (biliary) and 5% in urine. Pseudoephedrine: 90% excreted unchanged in urine; remainder undergoes hepatic N-demethylation.
Acetaminophen: 10-25% (albumin). Aspirin: 50-80% (albumin), dose-dependent; salicylate: 75-90% (albumin). Codeine: ~7% (albumin).
Fexofenadine: 60-70% bound to plasma proteins (albumin and α1-acid glycoprotein). Pseudoephedrine: negligible binding (<5%).
Acetaminophen: 0.9-1.0 L/kg (large distribution including liver). Aspirin: 0.15-0.2 L/kg (low Vd, confined to plasma and extracellular fluid); salicylate: 0.2-0.3 L/kg. Codeine: 3-6 L/kg (extensive tissue distribution). Clinical meaning: Large Vd for codeine suggests extensive tissue binding; aspirin Vd is small, consistent with limited extravascular distribution.
Fexofenadine: 3.3 L/kg (large Vd, extensive tissue distribution); pseudoephedrine: 2.6-3.5 L/kg (distributes into body water).
Oral: Acetaminophen: 85-95%. Aspirin: 40-60% (due to first-pass hydrolysis to salicylate). Codeine: ~50% due to first-pass metabolism.
Fexofenadine: 33% oral bioavailability (first-pass effect minimal, but absorption incomplete). Pseudoephedrine: ~90% oral bioavailability.
GFR 30-59 m L/min: Administer every 6 hours; maximum 6 tablets/day. GFR 15-29 m L/min: Administer every 12 hours; maximum 4 tablets/day. GFR <15 m L/min: Not recommended due to accumulation of codeine metabolites.
Contraindicated in severe renal impairment (Cr Cl < 30 m L/min). For mild to moderate impairment (Cr Cl 30-80 m L/min): fexofenadine dose adjustment recommended (not to exceed 60 mg once daily), but pseudoephedrine accumulation may occur; use alternative product. Not studied in ESRD.
Child-Pugh Class A: No adjustment. Child-Pugh Class B: Reduce dose by 50% and extend interval to every 6 hours; maximum 4 tablets/day. Child-Pugh Class C: Contraindicated.
No dosage adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not studied in severe hepatic impairment (Child-Pugh C); caution.
Not recommended for children <12 years due to aspirin risk of Reye syndrome. For children ≥12 years: Dose based on codeine component (0.5-1 mg/kg/dose) with maximum acetaminophen 75 mg/kg/day and aspirin 100 mg/kg/day. Typical: 1 tablet (acetaminophen 300 mg/aspirin 300 mg/codeine 30 mg) every 4-6 hours as needed; max 4 tablets/day.
Children under 12 years: not recommended. For children ≥12 years: same as adult dosing: 1 tablet every 12 hours with water.
Start with lowest effective dose (e.g., 1 tablet every 6 hours); monitor renal and hepatic function; maximum 6 tablets/day due to increased sensitivity and risk of adverse effects.
Elderly patients may be more sensitive to CNS effects and anticholinergic effects of pseudoephedrine. Not recommended due to increased risk of adverse reactions; consider alternative therapy. If used, monitor closely.
Risk of medication errors: confusion between different strengths and concentrations of acetaminophen can result in accidental overdose and fatal hepatotoxicity. Aspirin use in children and teenagers with viral infections is associated with Reye's syndrome.
None.
Hepatotoxicity (acetaminophen dose >4 g/day), Reye's syndrome (aspirin in children), respiratory depression (codeine), tolerance/dependence, bleeding risk (aspirin), GI toxicity, renal impairment, hypersensitivity reactions.
Cardiovascular effects: hypertension, arrhythmias, palpitations, tachycardia, myocardial infarction, stroke (especially with pre-existing cardiovascular disease or concomitant use with other sympathomimetics).,Central nervous system stimulation: nervousness, dizziness, insomnia, tremor, seizures (may be exacerbated in patients with seizure disorders).,Increased intraocular pressure: contraindicated in narrow-angle glaucoma.,Urinary retention: use with caution in patients with prostate hypertrophy or obstructive uropathy.,Thyroid disorders: may aggravate hyperthyroidism; use with caution.,Diabetes mellitus: may increase blood glucose; monitor in diabetic patients.,Acute allergic reactions: discontinue if severe hypersensitivity occurs.,Renal impairment: fexofenadine clearance reduced; avoid use in severe renal impairment (Cr Cl <30 m L/min).,Elderly: more sensitive to adverse effects; use with caution.,Drug interactions: MAO inhibitors (hypertensive crisis); antihypertensives (reduced effect); alcohol/CNS depressants (additive effects).
Hypersensitivity to any component, active peptic ulcer disease, bleeding disorders, severe hepatic impairment, severe respiratory depression, children with viral illness (aspirin), pregnancy (third trimester for aspirin, codeine cautious).
Hypersensitivity to fexofenadine, pseudoephedrine, or any component of the formulation.,Severe hypertension or coronary artery disease.,Narrow-angle glaucoma.,Urinary retention (e.g., due to bladder neck obstruction or prostatic hyperplasia).,Severe renal impairment (Cr Cl <30 m L/min).,Concurrent use or within 14 days of MAO inhibitor therapy (risk of hypertensive crisis).
Avoid alcohol due to increased risk of acetaminophen hepatotoxicity and aspirin-induced GI bleeding. Avoid large amounts of caffeine or high-tyramine foods (e.g., aged cheeses, cured meats) as they may affect CYP2D6 metabolism of codeine.
Avoid alcohol, which can increase drowsiness. Grapefruit juice may reduce absorption of fexofenadine; avoid concurrent intake. Taking with high-fat meal may slow absorption but not affect overall efficacy.
Acetaminophen: Generally considered low risk; association with ASD and ADHD with prolonged use not fully established. Aspirin: First trimester: possible increased risk of gastroschisis; second trimester: relatively safe; third trimester: risk of premature closure of ductus arteriosus, oligohydramnios, and increased peripartum hemorrhage. Codeine: First trimester: possible neural tube defects; second and third trimesters: risk of respiratory depression, withdrawal in neonate with chronic use; neonatal opioid withdrawal syndrome (NOWS) possible.
FDA Pregnancy Category C. First trimester: Animal studies show teratogenic effects at high doses of fexofenadine; pseudoephedrine may cause reduced uterine blood flow. Second and third trimesters: Risk of uterine contractions and fetal hypoxia due to pseudoephedrine vasoconstriction; avoid in preeclampsia.
Acetaminophen: M/P ratio approximately 0.91-1.42; considered safe. Aspirin: M/P ratio 0.08-0.15; high doses may cause Reye's syndrome; avoid or use low doses. Codeine: M/P ratio about 2.5; variable metabolism; risk of CNS depression in infant; avoid due to potential for toxicity in CYP2D6 ultrarapid metabolizers.
Fexofenadine: low excretion in breast milk (M/P ratio not established); pseudoephedrine: excreted in milk, may cause irritability and sleep disturbances in infants. Use caution, consider risk-benefit.
Acetaminophen: No dose adjustment needed. Aspirin: Avoid in third trimester; use lowest effective dose if necessary. Codeine: Avoid in pregnancy; if used, lowest effective dose for shortest duration; caution for CYP2D6 polymorphism. Pharmacokinetic changes: Increased clearance of codeine during pregnancy may require higher doses but risk outweighs benefit.
No specific dose adjustments recommended; use lowest effective dose for shortest duration due to altered pharmacokinetics (increased plasma volume, decreased GFR).
Combination analgesic with acetaminophen (hepatotoxic at high doses), aspirin (antiplatelet, GI irritant, contraindicated in children <12 due to Reye's syndrome), and codeine (prodrug to morphine via CYP2D6; efficacy depends on CYP2D6 phenotype; risk of CNS/respiratory depression). Avoid in severe hepatic/renal impairment, active peptic ulcer, bleeding disorders, or concomitant use of other CNS depressants. Maximum acetaminophen dose from all sources: 4 g/day.
Allegra-D 12 Hour contains fexofenadine (antihistamine) and pseudoephedrine (decongestant). Pseudoephedrine can cause insomnia, so advise taking the last dose early in the evening. Avoid in patients with severe hypertension, coronary artery disease, or narrow-angle glaucoma. Use with caution in hyperthyroidism, diabetes, and prostatic hypertrophy. Do not exceed recommended dose; extended-release formulation must be swallowed whole.
Do not exceed recommended dose; acetaminophen overdosage can cause serious liver damage.,Do not take with other products containing acetaminophen or aspirin.,Avoid alcohol while taking this medication to reduce risk of liver toxicity and GI bleeding.,This product contains aspirin; do not give to children/teenagers with chickenpox or flu-like symptoms to avoid Reye's syndrome.,May cause drowsiness; do not drive or operate machinery until you know how you react.,Codeine is a narcotic pain reliever with abuse potential; use exactly as prescribed.,Seek medical attention if you experience signs of allergic reaction (rash, difficulty breathing) or bleeding (black/tarry stools, unusual bruising).
Take this medication by mouth with or without food, usually every 12 hours.,Swallow the tablet whole; do not crush, chew, or break it.,Do not take more than 2 tablets in 24 hours.,Avoid taking at bedtime to prevent difficulty sleeping.,Do not take with other products containing pseudoephedrine or other decongestants.,Stop use and ask a doctor if symptoms do not improve within 7 days or are accompanied by fever.,Keep out of reach of children.
"Pirenzepine, a selective M1 muscarinic antagonist, reduces gastrointestinal motility and secretions, while codeine, an opioid agonist, also decreases gastrointestinal motility via mu-opioid receptors. Concurrent use leads to additive anticholinergic and opioid effects, resulting in enhanced risk of severe constipation, paralytic ileus, and central nervous system depression. Clinically, patients may experience exacerbated sedation, respiratory depression, and urinary retention."
"Ropinirole, a non-ergoline dopamine agonist used in Parkinson's disease and restless legs syndrome, may reduce the analgesic efficacy of codeine. This is likely due to pharmacodynamic antagonism at central dopamine and opioid receptors, as well as potential pharmacokinetic interactions that decrease the conversion of codeine to its active metabolite morphine via CYP2D6 inhibition by ropinirole. The resultant blunted opioid response can lead to inadequate pain control, necessitating dose adjustment or alternative therapy."
"Vemurafenib induces CYP3A4, significantly reducing the plasma concentrations of codeine, which is metabolized via CYP3A4 to its active metabolite morphine. This may diminish codeine's analgesic efficacy, potentially leading to inadequate pain control. Additionally, reduced formation of morphine may lower the risk of opioid-related adverse effects."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about ACETAMINOPHEN, ASPIRIN, AND CODEINE PHOSPHATE vs ALLEGRA-D 12 HOUR ALLERGY AND CONGESTION, answered by our medical review team.
ACETAMINOPHEN, ASPIRIN, AND CODEINE PHOSPHATE is a Opioid Agonist that works by Acetaminophen: cyclooxygenase (COX) inhibitor, primarily central, analgesic and antipyretic. Aspirin: irreversible COX-1 and COX-2 inhibitor, analgesic, anti-inflammatory, antipyretic, antiplatelet. Codeine: prodrug converted to morphine; mu-opioid receptor agonist.. ALLEGRA-D 12 HOUR ALLERGY AND CONGESTION is a Antihistamine-Decongestant Combination that works by Fexofenadine is a selective peripheral H1-receptor antagonist; pseudoephedrine is a sympathomimetic amine that directly stimulates alpha-adrenergic receptors, causing vasoconstriction and decongestion.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ACETAMINOPHEN, ASPIRIN, AND CODEINE PHOSPHATE and ALLEGRA-D 12 HOUR ALLERGY AND CONGESTION 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 ACETAMINOPHEN, ASPIRIN, AND CODEINE PHOSPHATE is: 1-2 tablets (each containing acetaminophen 300 mg, aspirin 300 mg, codeine phosphate 30 mg) orally every 4-6 hours as needed for pain; maximum 8 tablets/day.. The standard adult dose of ALLEGRA-D 12 HOUR ALLERGY AND CONGESTION is: Adults and children 12 years and older: 1 tablet (fexofenadine 60 mg/pseudoephedrine 120 mg) orally every 12 hours with water. Do not exceed 2 tablets in 24 hours.. 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 ACETAMINOPHEN, ASPIRIN, AND CODEINE PHOSPHATE and ALLEGRA-D 12 HOUR ALLERGY AND CONGESTION 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. ACETAMINOPHEN, ASPIRIN, AND CODEINE PHOSPHATE is classified as Category D/X. Acetaminophen: Generally considered low risk; association with ASD and ADHD with prolonged use not fully established. Aspirin: First trimester: possible increased risk of gastrosch. ALLEGRA-D 12 HOUR ALLERGY AND CONGESTION is classified as Category C. FDA Pregnancy Category C. First trimester: Animal studies show teratogenic effects at high doses of fexofenadine; pseudoephedrine may cause reduced uterine blood flow. Second and t. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.