Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
TYLENOL W/ CODEINE NO. 1 vs ACETAMINOPHEN AND CODEINE PHOSPHATE
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Codeine is a prodrug that undergoes O-demethylation via CYP2D6 to morphine, which acts as a μ-opioid receptor agonist. Acetaminophen inhibits cyclooxygenase (COX) enzymes in the CNS, reducing prostaglandin synthesis and modulating pain perception.
Acetaminophen: centrally acting analgesic and antipyretic, possibly via inhibition of cyclooxygenase (COX) and modulation of cannabinoid receptors. Codeine: prodrug converted to morphine; mu-opioid receptor agonist.
Mild to moderate pain,Pyrexia
Mild to moderate pain,Pain accompanied by fever
Adult: 1-2 tablets (acetaminophen 300 mg/codeine 8 mg per tablet) orally every 4-6 hours as needed; maximum 8 tablets per day. Route: oral. Frequency: every 4-6 hours.
One or two tablets (acetaminophen 300 mg/codeine 30 mg per tablet) orally every 4-6 hours as needed for pain; maximum 12 tablets daily.
Acetaminophen: 2-3 hours; Codeine: 2.5-3.5 hours; Morphine (active metabolite): 2-4 hours. Terminal half-life prolonged in hepatic impairment or elderly.
Acetaminophen: 2–3 hours (prolonged in hepatic impairment). Codeine: 2.5–3.5 hours; metabolites: morphine 1.5–2.5 hours, codeine-6-glucuronide 3–4 hours. Clinical context: dosing interval every 4–6 hours.
Acetaminophen is primarily metabolized via glucuronidation and sulfation in the liver, with a minor pathway via CYP2E1 to a toxic metabolite (NAPQI). Codeine is metabolized via CYP2D6 to morphine, via CYP3A4 to norcodeine, and via glucuronidation.
Acetaminophen: primarily glucuronidation and sulfation in liver; minor CYP450 (CYP2E1) to toxic NAPQI. Codeine: CYP2D6 to morphine; CYP3A4 to norcodeine; glucuronidation.
Renal: ~70-80% of codeine as inactive metabolites (codeine-6-glucuronide, norcodeine, morphine) and ~5-10% as unchanged codeine; ~5-15% of acetaminophen as unchanged drug. Biliary/fecal: minimal (<5% for both).
Acetaminophen: renal elimination of conjugated metabolites (glucuronide 60%, sulfate 30%, cysteine/mercapturate <5%), less than 5% unchanged. Codeine: renal elimination of codeine (5–15%), morphine (5–10%), norcodeine (10–20%), and conjugates; 90% excreted in urine within 24 hours.
Acetaminophen: 10-25% bound to plasma proteins; Codeine: ~25% bound to plasma proteins.
Acetaminophen: 10–25% (albumin). Codeine: 7–25% (primarily albumin).
Acetaminophen: ~0.9 L/kg (distributes throughout total body water); Codeine: ~3-6 L/kg (extensively distributed into tissues).
Acetaminophen: 0.9 L/kg. Codeine: 3–6 L/kg (extensive tissue distribution).
Acetaminophen: oral bioavailability ~80-85%; Codeine: oral bioavailability ~60-90% (due to first-pass metabolism to morphine).
Oral: acetaminophen 88% (variable first-pass); codeine 50–60% (first-pass metabolism to morphine, norcodeine, and conjugates).
Cr Cl 30-50 m L/min: Administer every 6 hours; Cr Cl <30 m L/min: Avoid due to risk of codeine accumulation and toxicity; hemodialysis: Not recommended.
GFR 30-50 m L/min: administer every 6 hours; GFR 10-29 m L/min: administer every 8 hours; GFR <10 m L/min: administer every 12 hours; hemodialysis: not recommended.
Child-Pugh Class A (mild): No adjustment needed; Child-Pugh Class B (moderate): Reduce dose by 50% and extend interval to every 6-8 hours; Child-Pugh Class C (severe): Contraindicated.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50% and extend interval to every 8 hours; Child-Pugh C: contraindicated.
Weight-based: Codeine not recommended in pediatric patients <12 years due to risk of respiratory depression; for ages 12-18 years: 1 tablet (acetaminophen 300 mg/codeine 8 mg) orally every 4-6 hours as needed; maximum 4 tablets per day.
For children ≥12 years: acetaminophen 10-15 mg/kg/dose and codeine 0.5-1 mg/kg/dose orally every 4-6 hours; maximum acetaminophen 75 mg/kg/day, codeine 6 mg/kg/day. For children <12 years: not recommended due to codeine safety concerns.
Start at lowest effective dose (1 tablet) and monitor for respiratory depression and constipation; consider acetaminophen 300 mg/codeine 8 mg every 6 hours; maximum 4 tablets per day.
Start with lowest effective dose; acetaminophen component maximum 3 g/day; consider reduced codeine dose (e.g., 15 mg) due to increased sensitivity and risk of respiratory depression; extend dosing interval to every 6-8 hours.
WARNING: RISK OF MEDICATION ERRORS; ADDICTION, ABUSE, AND MISUSE; RESPIRATORY DEPRESSION; ACCIDENTAL INGESTION; ULTRA-RAPID METABOLISM OF CODEINE AND OTHER RISK FACTORS FOR LIFE-THREATENING RESPIRATORY DEPRESSION IN CHILDREN; NEONATAL OPIOID WITHDRAWAL SYNDROME; INTERACTION WITH ALCOHOL; RISKS FROM CONCOMITANT USE WITH BENZODIAZEPINES OR OTHER CNS DEPRESSANTS; HEPATOTOXICITY.
Risk of medication errors: confusion between milligram and milliliter doses, and between codeine and acetaminophen components. Contraindicated for postoperative pain management in children following tonsillectomy/adenoidectomy due to risk of respiratory depression and death.
Risk of medication errors (confusion with other products),Addiction, abuse, and misuse,Life-threatening respiratory depression,Accidental ingestion (especially in children),Ultra-rapid metabolism of codeine (CYP2D6 ultra-rapid metabolizers),Neonatal opioid withdrawal syndrome with prolonged use during pregnancy,Hepatotoxicity (acetaminophen overdose),Severe hypotension,Seizures,Adrenal insufficiency,Serotonin syndrome with concomitant serotonergic drugs,Increased risk of severe skin reactions (e.g., SJS/TEN),Interaction with alcohol,Risks from concomitant use with benzodiazepines or other CNS depressants,Impaired mental/physical abilities,Use in children with respiratory conditions,Hepatic or renal impairment
Hepatotoxicity (acetaminophen overdose); respiratory depression; drug dependence; ultra-rapid metabolizers of codeine (CYP2D6) leading to morphine toxicity; concomitant CNS depressants; use in pediatric patients; avoid alcohol.
Hypersensitivity to codeine, acetaminophen, or any component,Significant respiratory depression,Acute or severe bronchial asthma in an unmonitored setting or without resuscitative equipment,Known or suspected gastrointestinal obstruction, including paralytic ileus,Patients with severe hepatic impairment or acute liver disease,Postoperative pain management in children who have had tonsillectomy and/or adenoidectomy,Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days of such therapy
Hypersensitivity to acetaminophen or codeine; severe respiratory depression; acute or severe asthma; paralytic ileus; post-operative pain management in children after tonsillectomy/adenoidectomy; breastfeeding (in ultra-rapid metabolizers); concomitant MAOIs.
Avoid alcohol; may increase risk of hepatotoxicity and CNS depression. No specific food restrictions. May be taken with food to reduce gastrointestinal upset.
Avoid alcohol; high-fat meals may delay absorption but not clinically significant.
Acetaminophen: Low teratogenic risk; use at therapeutic doses not associated with increased major malformations. Codeine: First trimester: Risk of malformations unclear; some studies suggest small increased risk of respiratory defects and spina bifida. Third trimester: Prolonged use may cause neonatal opioid withdrawal syndrome (NOWS); high doses near term may cause neonatal respiratory depression. Avoid chronic high doses.
Acetaminophen is considered low risk in all trimesters at therapeutic doses; chronic high doses may be associated with adverse outcomes. Codeine is associated with risk of respiratory depression and neonatal withdrawal if used near term; may cause neural tube defects and other malformations with first-trimester exposure, but data are conflicting. Use lowest effective dose for shortest duration.
Acetaminophen: Compatible; low levels in breast milk (M/P ratio ~0.91). Codeine: Excreted into breast milk; M/P ratio ~2.5. Risk of infant opioid toxicity, especially in ultra-rapid CYP2D6 metabolizers. Use lowest effective dose for shortest duration. Monitor infant for drowsiness, feeding difficulties, respiratory depression.
Acetaminophen is excreted into breast milk in low amounts (M/P ratio ~0.91-1.42) and is considered compatible with breastfeeding. Codeine is also excreted in breast milk; risk of infant opioid toxicity depends on maternal CYP2D6 phenotype. Ultra-rapid metabolizers may produce higher morphine levels. Use with caution, avoid in known CYP2D6 ultra-rapid metabolizers, and monitor infant for sedation and respiratory depression.
No standard dose adjustment required for acetaminophen. Codeine: Increased clearance in pregnancy may require dose adjustment; however, use lowest effective dose due to unpredictable metabolism. Avoid codeine in pregnancy if possible. Maximum recommended dose: acetaminophen 3000 mg/day; codeine 60 mg/day.
No routine dose adjustment needed for acetaminophen. Codeine pharmacokinetics are altered in pregnancy: increased clearance and volume of distribution may require dose adjustment; however, due to variability in CYP2D6 metabolism, individualize dosing and monitor for efficacy and toxicity. Avoid codeine in pregnancy unless alternative analgesics are ineffective.
Contains 300 mg acetaminophen and 15 mg codeine per tablet. Maximum acetaminophen dose 4000 mg/day; avoid combination with other acetaminophen products. Codeine is a prodrug requiring CYP2D6 conversion to morphine; poor metabolizers have reduced analgesia, ultra-rapid metabolizers risk toxicity. Monitor for respiratory depression, especially in children, elderly, or obese. Not recommended in breastfeeding mothers due to risk of infant toxicity.
For acute pain, limit codeine to 3 days; avoid in children under 12 due to CYP2D6 ultra-rapid metabolizer risk of fatal respiratory depression; monitor for constipation; assess liver function for acetaminophen hepatotoxicity; use with caution in renal impairment.
Do not exceed 13 tablets per 24 hours due to acetaminophen limit.,Avoid alcohol while taking this medication.,Do not use with any other products containing acetaminophen or codeine.,May cause drowsiness; avoid driving or operating machinery.,Store out of reach of children and dispose of unused medication properly.,Seek medical help if you experience difficulty breathing, severe drowsiness, or signs of allergic reaction.
Take exactly as prescribed; do not exceed 4000 mg acetaminophen per day.,Avoid alcohol while taking this medication.,Do not use with other acetaminophen-containing products.,May cause dizziness or drowsiness; avoid driving until you know how you react.,Common side effects include constipation, nausea, and drowsiness.,Seek emergency if signs of allergic reaction or difficulty breathing occur.
"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."
"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."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about TYLENOL W/ CODEINE NO. 1 vs ACETAMINOPHEN AND CODEINE PHOSPHATE, answered by our medical review team.
TYLENOL W/ CODEINE NO. 1 is a Opioid Agonist that works by Codeine is a prodrug that undergoes O-demethylation via CYP2D6 to morphine, which acts as a μ-opioid receptor agonist. Acetaminophen inhibits cyclooxygenase (COX) enzymes in the CNS, reducing prostaglandin synthesis and modulating pain perception.. ACETAMINOPHEN AND CODEINE PHOSPHATE is a Opioid Agonist that works by Acetaminophen: centrally acting analgesic and antipyretic, possibly via inhibition of cyclooxygenase (COX) and modulation of cannabinoid receptors. Codeine: prodrug converted to morphine; mu-opioid receptor agonist.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between TYLENOL W/ CODEINE NO. 1 and ACETAMINOPHEN AND CODEINE PHOSPHATE depend on the specific clinical indication. These are both Opioid Agonist agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of TYLENOL W/ CODEINE NO. 1 is: Adult: 1-2 tablets (acetaminophen 300 mg/codeine 8 mg per tablet) orally every 4-6 hours as needed; maximum 8 tablets per day. Route: oral. Frequency: every 4-6 hours.. The standard adult dose of ACETAMINOPHEN AND CODEINE PHOSPHATE is: One or two tablets (acetaminophen 300 mg/codeine 30 mg per tablet) orally every 4-6 hours as needed for pain; maximum 12 tablets daily.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
A moderate-severity drug interaction has been identified when combining TYLENOL W/ CODEINE NO. 1 and ACETAMINOPHEN AND CODEINE PHOSPHATE. Codeine, a prodrug converted to morphine via CYP2D6, and metyrosine, a tyrosine hydroxylase inhibitor, synergistically depress the central nervous system. Codeine's mu-opioid receptor agonism and metyrosine's reduction of catecholamine synthesis lead to enhanced sedation, respiratory depression, and hypotension. Clinically, patients may experience excessive drowsiness, confusion, or respiratory compromise, particularly at higher doses or in vulnerable populations. Consult your prescriber before combining these medications.
The maternal-fetal safety profiles differ. TYLENOL W/ CODEINE NO. 1 is classified as Category D/X. Acetaminophen: Low teratogenic risk; use at therapeutic doses not associated with increased major malformations. Codeine: First trimester: Risk of malformations unclear; some studi. ACETAMINOPHEN AND CODEINE PHOSPHATE is classified as Category D/X. Acetaminophen is considered low risk in all trimesters at therapeutic doses; chronic high doses may be associated with adverse outcomes. Codeine is associated with risk of respirat. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.