Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
PROPOXYPHENE HYDROCHLORIDE AND ACETAMINOPHEN vs ANEXSIA 5/325
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Propoxyphene is a mu-opioid receptor agonist; acetaminophen inhibits cyclooxygenase (COX) and modulates central pain pathways.
Hydrocodone is a semi-synthetic opioid agonist that binds to mu-opioid receptors in the CNS, inhibiting ascending pain pathways and altering pain perception. Acetaminophen is a para-aminophenol derivative with analgesic and antipyretic effects, primarily through central COX-2 inhibition and activation of descending serotonergic pathways.
Mild to moderate pain,Cough suppression (off-label)
Management of moderate to moderately severe pain where an opioid analgesic is appropriate
One tablet (propoxyphene HCl 65 mg/acetaminophen 650 mg) orally every 4 hours as needed for pain; maximum: 6 tablets per day.
1-2 tablets orally every 4-6 hours as needed for pain; maximum 8 tablets per day.
Propoxyphene: 6-12 h (prolonged in hepatic disease); Norpropoxyphene (active metabolite): 30-36 h (accumulation risk). Acetaminophen: 2-3 h (prolonged in hepatic disease).
Oxycodone: terminal half-life 3.2-4.3 hours (immediate-release); prolonged in hepatic impairment. Acetaminophen: terminal half-life 2-3 hours (therapeutic doses); prolonged in hepatic impairment or overdose.
Propoxyphene: hepatic via CYP3A4 and CYP2D6 to norpropoxyphene (active); acetaminophen: hepatic via conjugation (glucuronidation, sulfation) and CYP2E1.
Hydrocodone: primarily hepatic via CYP3A4 and CYP2D6 to active metabolites (hydromorphone). Acetaminophen: hepatic metabolism via conjugation (glucuronidation, sulfation) and CYP2E1-mediated oxidation to toxic NAPQI.
Renal: Propoxyphene ~20-25% as unchanged drug and metabolites; Acetaminophen ~85-90% as glucuronide and sulfate conjugates, <5% unchanged. Fecal: Minimal for both.
Oxycodone: renal excretion of metabolites (conjugated and unconjugated) and parent drug; ~10% excreted unchanged. Acetaminophen: renal excretion of metabolites (glucuronide and sulfate conjugates); ~2-4% excreted unchanged.
Propoxyphene: ~80% bound to albumin; Acetaminophen: 10-25% bound to albumin at therapeutic concentrations.
Oxycodone: 38-45% bound to albumin and alpha-1-acid glycoprotein. Acetaminophen: 10-25% bound to albumin at therapeutic concentrations.
Propoxyphene: 12-26 L/kg (large, extensive tissue distribution; clinical meaning: high CNS penetration). Acetaminophen: 0.9-1.0 L/kg (clinical meaning: uniform distribution, limited tissue binding).
Oxycodone: Vd 2.0-3.0 L/kg; distributes extensively into tissues. Acetaminophen: Vd 0.8-1.0 L/kg; relatively uniform distribution.
Oral: Propoxyphene ~30-70% due to extensive first-pass metabolism; Acetaminophen ~85-90%.
Oxycodone: oral bioavailability 60-87% (immediate-release). Acetaminophen: oral bioavailability 88-98% (therapeutic doses).
Not recommended in severe renal impairment (Cr Cl <30 m L/min). For moderate impairment (Cr Cl 30-50 m L/min), reduce frequency to every 6-8 hours; use with caution.
GFR 30-50 m L/min: use with caution, increase dosing interval to every 6 hours; GFR <30 m L/min: avoid use due to hydrocodeone accumulation.
Contraindicated in severe hepatic impairment (Child-Pugh C). For Child-Pugh A or B, reduce dose by 50% and monitor hepatic function; maximum duration limited.
Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50% and monitor; Child-Pugh C: contraindicated.
Not recommended for pediatric use due to risk of respiratory depression and propoxyphene toxicity; safety and efficacy not established.
Not recommended for children under 18 years due to risk of respiratory depression.
Initiate with lower doses (e.g., half tablet) and increase cautiously; avoid in elderly with renal or hepatic impairment; monitor for CNS and respiratory effects.
Start with lowest dose (1 tablet every 6 hours), monitor renal and hepatic function, and avoid in frail elderly due to increased fall and cognitive impairment risk.
Risk of respiratory depression, addiction, abuse, and misuse; concomitant use with benzodiazepines or CNS depressants may cause profound sedation, respiratory depression, coma, and death.
Risk of addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion; neonatal opioid withdrawal syndrome; risks from concomitant use with benzodiazepines or other CNS depressants; and hepatotoxicity from acetaminophen overdose.
Respiratory depression risk,Abuse and dependence potential,CNS depression with alcohol or other drugs,Hepatotoxicity from acetaminophen overdose,QT prolongation with high doses,Neonatal opioid withdrawal syndrome with prolonged use during pregnancy
Risk of opioid addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion; neonatal opioid withdrawal syndrome; risks from concomitant use with benzodiazepines or other CNS depressants; hepatotoxicity; adrenal insufficiency; severe hypotension; gastrointestinal obstruction; seizure; and serotonin syndrome.
Hypersensitivity to propoxyphene or acetaminophen,Significant respiratory depression,Acute or severe bronchial asthma,Paralytic ileus,Concurrent alcohol use (risk of hepatotoxicity),MAO inhibitor use within 14 days,Known prolonged QT interval or on QT-prolonging drugs
Hypersensitivity to hydrocodone or acetaminophen; significant respiratory depression; acute or severe bronchial asthma; GI obstruction; known or suspected paralytic ileus; severe hepatic impairment; and concurrent use of MAOIs within 14 days.
Avoid alcohol; may increase risk of hepatotoxicity and CNS depression. High-fat meals may delay absorption but not clinically significant.
Avoid alcohol. Grapefruit juice may enhance side effects; limit intake. Take with food to reduce gastrointestinal discomfort.
Propoxyphene is contraindicated in pregnancy due to risk of neonatal opioid withdrawal syndrome and respiratory depression. Acetaminophen is generally considered safe in pregnancy at therapeutic doses. First trimester: Propoxyphene may increase risk of congenital malformations, though data are limited. Second/third trimester: Prolonged use may cause neonatal opioid withdrawal; high doses near term may cause respiratory depression in the neonate.
First trimester: Associated with increased risk of neural tube defects and cardiovascular malformations; avoid use. Second and third trimesters: Chronic exposure may cause fetal renal toxicity, oligohydramnios, and premature closure of ductus arteriosus. Use only if clearly needed.
Propoxyphene is excreted into breast milk in low concentrations (M/P ratio approximately 0.5); however, the combination with acetaminophen may pose risks of sedation and respiratory depression in the infant. Acetaminophen is considered compatible with breastfeeding. Use with caution, monitor infant for drowsiness and feeding difficulties.
Paracetamol and hydrocodone are excreted in breast milk. M/P ratio: paracetamol ~1.0, hydrocodone ~1.0-2.0. Use with caution; monitor infant for drowsiness and respiratory depression. Consider risk of infant sedation with long-term use.
No specific dosing adjustments for propoxyphene/acetaminophen in pregnancy are established. However, pregnancy can alter propoxyphene pharmacokinetics (e.g., increased clearance, volume of distribution); thus, doses may need adjustment based on clinical response and toxicity monitoring. Generally, lowest effective dose for shortest duration is recommended.
Increased clearance in pregnancy may require dose adjustment. Monitor for pain control and adverse effects; no fixed dose change recommended. Consider lower starting dose due to potential fetal risks. Avoid chronic use; taper if possible.
Propoxyphene is a weak opioid with a narrow therapeutic index; acetaminophen component limits daily dose due to hepatotoxicity risk. Propoxyphene has been withdrawn in many countries due to cardiotoxicity (QT prolongation, arrhythmias) and overdose risks. Avoid in elderly due to accumulation of norpropoxyphene metabolite. Use with caution in renal impairment. Monitor for CNS depression when combined with other depressants.
ANEXSIA 5/325 contains hydrocodone 5 mg and acetaminophen 325 mg. Maximum acetaminophen dose from all sources should not exceed 4 g/day in adults; avoid in severe hepatic impairment. Hydrocodone is a Schedule II controlled substance with abuse potential; monitor for respiratory depression, especially in opioid-naive patients. Use with caution in patients with COPD, sleep apnea, or increased intracranial pressure. Consider naloxone co-prescription for high-risk patients. For acute pain, limit duration to 3-7 days.
Do not exceed recommended dose; acetaminophen overdose can cause severe liver damage.,Propoxyphene may cause dizziness, drowsiness, or confusion; avoid driving or operating machinery.,Avoid alcohol and other CNS depressants during therapy.,Inform your doctor if you have a history of heart rhythm problems, as propoxyphene can affect heart rhythm.,Do not stop abruptly after prolonged use; withdrawal may occur.
Take exactly as prescribed; do not increase dose or frequency without consulting your doctor.,Do not consume alcohol or other sedatives (e.g., benzodiazepines) while taking this medication.,Avoid other products containing acetaminophen (e.g., Tylenol, cold remedies) to prevent liver damage.,This medication may cause drowsiness or dizziness; do not drive or operate machinery until you know how it affects you.,Store securely out of reach of others; dispose of unused medication via drug take-back programs.,Seek emergency help if you have trouble breathing, severe drowsiness, or signs of allergic reaction.
"Acetaminophen competitively inhibits the CYP3A4 isoenzyme, which is the primary metabolic pathway for nilotinib. This reduces nilotinib clearance, leading to increased systemic exposure and potentially enhanced toxicity, including QT prolongation and hepatotoxicity. Clinically, coadministration may raise nilotinib plasma concentrations by 20-40%, warranting caution especially in patients with hepatic impairment or on high-dose acetaminophen."
"Rilpivirine, a non-nucleoside reverse transcriptase inhibitor (NNRTI), is primarily metabolized by CYP3A4 enzymes. Acetaminophen is principally metabolized via conjugation pathways (glucuronidation and sulfation) with minor oxidation via CYP2E1, CYP1A2, and CYP3A4. While Rilpivirine is not a known inhibitor of acetaminophen metabolism, weak inhibition of CYP3A4 by rilpivirine may theoretically reduce acetaminophen clearance, leading to a modest increase in acetaminophen serum concentrations. This interaction is unlikely to be clinically significant in most patients, but could theoretically increase the risk of hepatotoxicity with supratherapeutic doses."
"Acetaminophen undergoes glucuronidation and sulfation, with minor cytochrome P450 (CYP) 3A4 metabolism, while efavirenz is a potent inducer of CYP3A4. Chronic co-administration may modestly increase acetaminophen clearance, reducing its efficacy. However, the primary safety concern is that efavirenz does not significantly impact acetaminophen hepatotoxicity risk; conversely, acetaminophen at therapeutic doses does not alter efavirenz pharmacokinetics. No clinically significant interaction is established, and the combination is generally safe when used as directed."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about PROPOXYPHENE HYDROCHLORIDE AND ACETAMINOPHEN vs ANEXSIA 5/325, answered by our medical review team.
PROPOXYPHENE HYDROCHLORIDE AND ACETAMINOPHEN is a Opioid Analgesic Combination that works by Propoxyphene is a mu-opioid receptor agonist; acetaminophen inhibits cyclooxygenase (COX) and modulates central pain pathways.. ANEXSIA 5/325 is a Opioid Analgesic Combination that works by Hydrocodone is a semi-synthetic opioid agonist that binds to mu-opioid receptors in the CNS, inhibiting ascending pain pathways and altering pain perception. Acetaminophen is a para-aminophenol derivative with analgesic and antipyretic effects, primarily through central COX-2 inhibition and activation of descending serotonergic pathways.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between PROPOXYPHENE HYDROCHLORIDE AND ACETAMINOPHEN and ANEXSIA 5/325 depend on the specific clinical indication. These are both Opioid Analgesic Combination agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of PROPOXYPHENE HYDROCHLORIDE AND ACETAMINOPHEN is: One tablet (propoxyphene HCl 65 mg/acetaminophen 650 mg) orally every 4 hours as needed for pain; maximum: 6 tablets per day.. The standard adult dose of ANEXSIA 5/325 is: 1-2 tablets orally every 4-6 hours as needed for pain; maximum 8 tablets per 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 PROPOXYPHENE HYDROCHLORIDE AND ACETAMINOPHEN and ANEXSIA 5/325 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. PROPOXYPHENE HYDROCHLORIDE AND ACETAMINOPHEN is classified as Category C. Propoxyphene is contraindicated in pregnancy due to risk of neonatal opioid withdrawal syndrome and respiratory depression. Acetaminophen is generally considered safe in pregnancy . ANEXSIA 5/325 is classified as Category C. First trimester: Associated with increased risk of neural tube defects and cardiovascular malformations; avoid use. Second and third trimesters: Chronic exposure may cause fetal re. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.