Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
DARVOCET vs ANEXSIA
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Darvocet is a combination of propoxyphene, a mu-opioid receptor agonist that alters perception of and response to pain, and acetaminophen, which inhibits COX enzymes and modulates descending serotonergic pathways.
ANEXSIA is a combination of hydrocodone and acetaminophen. Hydrocodone is an opioid agonist that binds to mu-opioid receptors in the central nervous system, altering pain perception and emotional response to pain. Acetaminophen's analgesic mechanism is not fully understood but involves inhibition of COX enzymes in the CNS and modulation of descending serotonergic pathways.
FDA-approved: relief of mild to moderate pain,Off-label: none commonly recognized
Relief of moderate to moderately severe pain
1 tablet (propoxyphene 100 mg / acetaminophen 650 mg) orally every 4 hours as needed for pain; maximum 6 tablets per day.
50-100 mg orally every 4-6 hours as needed; maximum 400 mg/day.
Propoxyphene: 6-12 hours (parent), 30-36 hours (norpropoxyphene). Acetaminophen: 1-4 hours (therapeutic doses). Accumulation of norpropoxyphene occurs with repeated dosing.
Terminal elimination half-life is 4-6 hours in adults with normal renal function; prolonged to 12-24 hours in severe renal impairment (Cr Cl <30 m L/min).
Propoxyphene: extensively metabolized via CYP3A4 to norpropoxyphene (active metabolite); Acetaminophen: metabolized primarily via glucuronidation and sulfation, with minor CYP2E1 oxidation.
Hydrocodone is metabolized via CYP2D6 and CYP3A4 to hydromorphone and norhydrocodone. Acetaminophen is primarily metabolized via hepatic glucuronidation and sulfation; a minor pathway via CYP2E1 produces NAPQI, which is detoxified by glutathione.
Propoxyphene: primarily hepatic metabolism to norpropoxyphene, renal excretion of metabolites (<1% unchanged). Acetaminophen: renal excretion of conjugates (85-90%) and unchanged drug (2-4%).
Approximately 70% renal (unchanged drug and metabolites), 20% biliary/fecal, 10% other.
Propoxyphene: 80% bound to albumin. Acetaminophen: 10-25% bound to albumin.
Approximately 95% bound to plasma albumin and alpha-1-acid glycoprotein.
Propoxyphene: 10-16 L/kg (large due to lipophilicity). Acetaminophen: 0.9-1.0 L/kg (distributes evenly in body fluids).
0.2-0.4 L/kg, indicating limited extravascular distribution primarily confined to plasma and interstitial fluid.
Propoxyphene: oral bioavailability ~40% due to first-pass metabolism. Acetaminophen: oral bioavailability 80-90%.
Oral: 80-90%; Intramuscular: 90-100%; Rectal: 70-80%.
For creatinine clearance <50 m L/min: avoid use; propoxyphene accumulates causing CNS and cardiac toxicity. For 50–80 m L/min: reduce frequency to every 6 hours. Not recommended in ESRD or dialysis.
GFR 30-89 m L/min: no adjustment; GFR 15-29 m L/min: 50% dose reduction; GFR <15 m L/min: avoid use.
Child-Pugh Class A: cautious use, reduce dose by 50% and monitor. Child-Pugh Class B or C: contraindicated due to risk of hepatotoxicity from acetaminophen and altered propoxyphene metabolism.
Child-Pugh A: no adjustment; Child-Pugh B: 50% dose reduction; Child-Pugh C: avoid use.
Not recommended for pediatric use due to risk of serious adverse effects; safety and efficacy not established.
1-2 mg/kg/dose orally every 6 hours; maximum 6 mg/kg/day.
Start with 1 tablet (100/650 mg) every 6 hours; maximum 4 tablets per day. Avoid in patients with renal impairment or multiple comorbidities. Increased risk of CNS depression and falls.
Initiate at 25 mg every 6 hours; increase cautiously; monitor renal function.
Propoxyphene has been withdrawn from the US market due to risk of fatal overdose; Darvocet is no longer available in the US.
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 from acetaminophen.
Respiratory depression, QT prolongation (propoxyphene), hepatotoxicity (acetaminophen at high doses), abuse potential, interaction with alcohol and CNS depressants.
Risk of respiratory depression, especially in elderly or debilitated patients; adrenal insufficiency; severe hypotension; seizures; opioid-induced hyperalgesia; acetaminophen hepatotoxicity (avoid exceeding 4 g/day); serotonin syndrome if used with serotonergic agents.
Hypersensitivity to propoxyphene or acetaminophen, severe asthma or respiratory depression, known CYP3A4 inhibitors (risk of increased propoxyphene levels), concurrent use of alcohol or other CNS depressants.
Hypersensitivity to hydrocodone or acetaminophen; significant respiratory depression; acute or severe bronchial asthma in an unmonitored setting; known or suspected GI obstruction; severe hepatic impairment; concomitant use of MAOIs or within 14 days.
Avoid alcohol. No specific food interactions, but take with food if gastrointestinal upset occurs. Maintain adequate hydration and fiber intake to prevent constipation.
Avoid alcohol; may increase risk of hepatotoxicity and GI bleeding. Limit caffeine intake from coffee, tea, cola, or energy drinks due to added caffeine content. High-fat meals may delay absorption; take on empty stomach for faster onset if tolerated.
Pregnancy Category C. First trimester: No evidence of structural malformations from acetaminophen; propoxyphene has not been associated with increased risk of major birth defects. Second and third trimesters: Chronic use may lead to neonatal withdrawal syndrome (irritability, hypertonia, tremors) and respiratory depression. High-dose or prolonged use near term associated with neonatal respiratory depression.
First trimester: Data are limited; no increased risk of major malformations reported in small studies. Second and third trimesters: Associated with premature closure of the ductus arteriosus and oligohydramnios due to fetal renal effects; avoid use after 30 weeks gestation.
Excreted in breast milk. Acetaminophen: M/P ratio 0.9-1.4; low infant dose. Propoxyphene: M/P ratio ~0.5; estimated infant dose <1% of maternal weight-adjusted dose. Considered compatible with breastfeeding if used short-term; monitor infant for drowsiness, poor feeding.
Excreted into breast milk in low concentrations (M/P ratio not established). Not recommended during breastfeeding due to potential for adverse effects in the infant, including renal impairment and gastrointestinal bleeding.
No standard dose adjustment recommended. Increased clearance of acetaminophen in pregnancy may require higher doses for efficacy; avoid exceeding 4 g/day. Propoxyphene pharmacokinetics not significantly altered; avoid prolonged use due to accumulation risk.
Dose adjustment not generally required; however, due to increased renal clearance in pregnancy, shortened dosing intervals may be necessary for sustained efficacy. Use lowest effective dose for shortest duration.
Darvocet contains propoxyphene, a weak opioid with potential for cardiac toxicity (QT prolongation) at high doses. Avoid in patients with history of substance abuse, suicidal ideation, or concurrent use of CNS depressants. Efficacy similar to aspirin, but with higher risk of adverse effects; consider safer alternatives. Monitor for respiratory depression in elderly or debilitated patients.
ANEXSIA is a combination analgesic containing paracetamol, ibuprofen, and caffeine. It is contraindicated in patients with active peptic ulcer disease, severe hepatic impairment, or hypersensitivity to NSAIDs. Avoid concurrent use with other NSAIDs or paracetamol-containing products. Monitor renal function in elderly or dehydrated patients. Caffeine may exacerbate anxiety or insomnia.
Take exactly as prescribed; do not take more than recommended dose.,Avoid alcohol and other CNS depressants (e.g., benzodiazepines) as they increase risk of serious side effects.,Do not drive or operate heavy machinery until you know how this medication affects you.,Do not stop abruptly; withdrawal may occur. Taper under medical supervision.,Report severe constipation, difficulty breathing, or signs of allergic reaction.,Store securely away from children and others; dispose properly when no longer needed.
Do not exceed recommended dose; overdosage of paracetamol can cause liver damage.,Take with food or milk to reduce gastrointestinal upset.,Avoid alcohol while taking this medication to reduce risk of liver toxicity and GI bleeding.,Discontinue use and consult if signs of allergic reaction, GI bleeding, or liver problems occur.,Caffeine may cause nervousness, insomnia, or increased heart rate; limit caffeine-containing foods and beverages.
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 DARVOCET vs ANEXSIA, answered by our medical review team.
DARVOCET is a Opioid Analgesic Combination that works by Darvocet is a combination of propoxyphene, a mu-opioid receptor agonist that alters perception of and response to pain, and acetaminophen, which inhibits COX enzymes and modulates descending serotonergic pathways.. ANEXSIA is a Opioid Analgesic Combination that works by ANEXSIA is a combination of hydrocodone and acetaminophen. Hydrocodone is an opioid agonist that binds to mu-opioid receptors in the central nervous system, altering pain perception and emotional response to pain. Acetaminophen's analgesic mechanism is not fully understood but involves inhibition of COX enzymes in the CNS and modulation of descending serotonergic pathways.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between DARVOCET and ANEXSIA 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 DARVOCET is: 1 tablet (propoxyphene 100 mg / acetaminophen 650 mg) orally every 4 hours as needed for pain; maximum 6 tablets per day.. The standard adult dose of ANEXSIA is: 50-100 mg orally every 4-6 hours as needed; maximum 400 mg/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 DARVOCET and ANEXSIA 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. DARVOCET is classified as Category C. Pregnancy Category C. First trimester: No evidence of structural malformations from acetaminophen; propoxyphene has not been associated with increased risk of major birth defects. . ANEXSIA is classified as Category C. First trimester: Data are limited; no increased risk of major malformations reported in small studies. Second and third trimesters: Associated with premature closure of the ductus . Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.