Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NUMORPHAN vs ANEXSIA
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Opioid agonist; binds to mu-opioid receptors in the CNS, inhibiting ascending pain pathways and altering pain perception.
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.
Moderate to severe pain where an opioid analgesic is appropriate,Anesthesia adjunct (off-label)
Relief of moderate to moderately severe pain
Intravenous or subcutaneous: 0.5-2 mg (0.1-0.2 mg/kg for severe pain) every 2-3 hours as needed; not to exceed 20 mg/day.
50-100 mg orally every 4-6 hours as needed; maximum 400 mg/day.
Terminal elimination half-life is 2–3 hours in adults; prolonged to 3–4 hours in elderly and up to 15 hours in patients with severe hepatic impairment.
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).
Primarily hepatic via glucuronidation; involves UGT2B7; active metabolite (hydromorphone-3-glucuronide) may accumulate in renal impairment.
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.
Primarily renal (approximately 70% as unchanged drug, <5% as noroxymorphone and other conjugates); biliary/fecal excretion accounts for ~20%.
Approximately 70% renal (unchanged drug and metabolites), 20% biliary/fecal, 10% other.
Approximately 10–20% bound to plasma proteins (primarily albumin).
Approximately 95% bound to plasma albumin and alpha-1-acid glycoprotein.
2.5–3.5 L/kg; indicates extensive tissue distribution, with high affinity for brain and other tissues.
0.2-0.4 L/kg, indicating limited extravascular distribution primarily confined to plasma and interstitial fluid.
Intravenous: 100%; Intramuscular: approximately 85–95%; Subcutaneous: approximately 75–85%; Oral: approximately 10–20% due to extensive first-pass metabolism.
Oral: 80-90%; Intramuscular: 90-100%; Rectal: 70-80%.
Cr Cl 10-50 m L/min: administer 75% of dose; Cr Cl <10 m L/min: administer 50% of dose, use with caution, consider extended dosing intervals.
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 B: reduce dose by 50%; Child-Pugh Class C: reduce dose by 75% or avoid use; start at lowest dose and titrate carefully.
Child-Pugh A: no adjustment; Child-Pugh B: 50% dose reduction; Child-Pugh C: avoid use.
Children >2 years: 0.1-0.2 mg/kg intravenously, subcutaneously, or intramuscularly every 2-4 hours as needed; not to exceed 15 mg/day.
1-2 mg/kg/dose orally every 6 hours; maximum 6 mg/kg/day.
Start at low end of dosing range (0.5 mg), extend dosing interval to 3-4 hours, monitor for respiratory depression and constipation, use non-opioid alternatives when possible.
Initiate at 25 mg every 6 hours; increase cautiously; monitor renal function.
Risk of respiratory depression, especially in elderly, cachectic, or debilitated patients; concomitant use with benzodiazepines or CNS depressants may cause profound sedation, respiratory depression, coma, and death; abuse potential leading to addiction; neonatal opioid withdrawal syndrome with prolonged use during pregnancy.
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; CNS depression; serotonin syndrome (with serotonergic drugs); adrenal insufficiency; hypotension; seizures; opioid-induced hyperalgesia; impaired ability to drive/operate machinery; risk of overdose with alcohol or other 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 hydromorphone or any component; significant respiratory depression; acute or severe bronchial asthma; known or suspected paralytic ileus; concurrent use of MAOIs (or within 14 days).
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 and grapefruit juice. Grapefruit juice may inhibit CYP3A4 metabolism of oxymorphone, leading to increased plasma concentrations and risk of toxicity. High-fat meals may delay absorption but not significantly alter overall exposure. Maintain adequate hydration 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.
First trimester: Limited data, but opioid use is associated with neural tube defects and congenital heart defects in some studies. Second and third trimesters: Chronic use may lead to fetal opioid dependence and neonatal withdrawal syndrome. No specific malformation pattern attributed to Numorphan. Avoid prolonged use, especially in first trimester.
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.
Numorphan (oxymorphone) is excreted into breast milk. The M/P ratio is unknown. Limited data suggest low concentrations, but caution is advised. Monitor infant for drowsiness, respiratory depression, and withdrawal if maternal use is prolonged. American Academy of Pediatrics considers it compatible with breastfeeding with cautious use, but consider risk-benefit.
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.
Pregnancy increases renal blood flow and hepatic metabolism; clearance of oxymorphone may be increased. No formal studies available. Consider dose adjustments based on clinical response and tolerability. Avoid in first trimester if possible; if necessary, use lowest effective dose for shortest duration. In third trimester, anticipate potential neonatal withdrawal and plan for taper postpartum.
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.
Numorphan (oxymorphone) is a potent semisynthetic opioid agonist approximately 10 times more potent than morphine. Avoid in patients with severe respiratory depression, paralytic ileus, or acute asthma. Caution in elderly, cachectic, or debilitated patients due to increased risk of respiratory depression. Monitor for hypotension and bradycardia. Use with extreme caution in patients with head injury or increased intracranial pressure. Abrupt discontinuation may precipitate withdrawal; taper gradually.
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 increase dose or frequency without consulting your doctor.,Numorphan may cause dizziness, drowsiness, or blurred vision; avoid driving or operating heavy machinery until you know how the drug affects you.,Avoid alcohol and other central nervous system depressants (e.g., sedatives, tranquilizers) as they may increase the risk of serious side effects like respiratory depression.,If you miss a dose, skip it and take the next dose at the scheduled time; do not double up.,Do not suddenly stop taking this medication; a gradual reduction under medical supervision is needed to prevent withdrawal symptoms.,Store securely away from children and pets; dispose of unused medication via a drug take-back program.
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 NUMORPHAN vs ANEXSIA, answered by our medical review team.
NUMORPHAN is a Opioid Analgesic that works by Opioid agonist; binds to mu-opioid receptors in the CNS, inhibiting ascending pain pathways and altering pain perception.. 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 NUMORPHAN and ANEXSIA 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 NUMORPHAN is: Intravenous or subcutaneous: 0.5-2 mg (0.1-0.2 mg/kg for severe pain) every 2-3 hours as needed; not to exceed 20 mg/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 NUMORPHAN 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. NUMORPHAN is classified as Category C. First trimester: Limited data, but opioid use is associated with neural tube defects and congenital heart defects in some studies. Second and third trimesters: Chronic use may lead. 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.