Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
APADAZ vs ALFENTANIL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
APADAZ is a combination of benzhydrocodone, a prodrug of hydrocodone, and acetaminophen. Hydrocodone acts as a full mu-opioid receptor agonist, inhibiting ascending pain pathways and altering pain perception. Acetaminophen's mechanism involves inhibition of cyclooxygenase (COX) enzymes, particularly in the CNS, and modulation of serotonergic pathways, contributing to analgesia and antipyresis.
Alfentanil is a potent, short-acting synthetic opioid analgesic that primarily acts as a mu-opioid receptor agonist. It binds to mu-opioid receptors in the central nervous system, leading to G-protein coupled activation of inwardly rectifying potassium channels and inhibition of voltage-gated calcium channels, resulting in hyperpolarization and reduced neurotransmitter release. This produces analgesia, sedation, and respiratory depression.
Management of acute pain severe enough to require an opioid analgesic and for which alternative treatments are inadequate
Analgesic adjunct during general anesthesia,Induction of anesthesia,Maintenance of anesthesia for short surgical procedures,Off-label: Procedural sedation in monitored settings
Each tablet contains benzhydrocodone 4.08 mg (hydrocodone 3.33 mg) and acetaminophen 325 mg. One to 2 tablets every 4 to 6 hours as needed for pain; maximum 12 tablets per 24 hours.
Initial IV bolus of 5-20 mcg/kg; maintenance infusion of 0.5-1.5 mcg/kg/min; incremental boluses of 5-10 mcg/kg as needed. Induction of anesthesia: 50-100 mcg/kg IV.
Terminal elimination half-life: 2-4 hours for benzhydrocodone; context: immediate-release, dosing every 4-6 hours.
Terminal elimination half-life: 90–111 minutes (1.5–1.85 hours). Clinically, context-sensitive half-time is short (~40 min after 3-hour infusion) due to rapid redistribution and metabolism.
Benzhydrocodone is converted to hydrocodone by intestinal and hepatic enzymes (e.g., esterases). Hydrocodone is metabolized via CYP3A4 and CYP2D6 to norhydrocodone, hydromorphone, and other metabolites. Acetaminophen is primarily metabolized by glucuronidation (UGT1A1, UGT1A6, UGT1A9) and sulfation (SULT1A1, SULT1A3); a minor amount is oxidized by CYP2E1, CYP1A2, and CYP3A4 to the reactive metabolite NAPQI, which is conjugated with glutathione.
Alfentanil is primarily metabolized by hepatic cytochrome P450 enzymes, mainly CYP3A4, through oxidative N-dealkylation and O-demethylation to inactive metabolites.
Renal: ~90% as conjugates, ~10% unchanged; fecal: minimal; enterohepatic recirculation occurs.
Primarily hepatic metabolism via CYP3A4; <1% excreted unchanged in urine; metabolites (mainly noralfentanil) excreted renally. Biliary/fecal excretion of metabolites accounts for ~30%.
Benzhydrocodone: ~20% bound to albumin; acetaminophen: 10-25% bound.
~92% bound primarily to alpha-1-acid glycoprotein (AAG) and albumin.
Benzhydrocodone: ~3-5 L/kg; context: extensive tissue distribution.
Vd: 0.4–1.0 L/kg (mean ~0.75 L/kg). Moderate Vd reflecting rapid distribution to tissues, especially brain and muscle.
Oral: ~50% for benzhydrocodone (due to first-pass metabolism); acetaminophen: 60-90%.
IV: 100%. IM: ~90%. Epidural: ~30–50% due to local uptake and redistribution. No significant oral bioavailability.
Contraindicated in severe renal impairment (e GFR <30 m L/min/1.73m²). For moderate impairment (e GFR 30-59 m L/min/1.73m²), initiate with lowest dose and monitor; do not exceed 6 tablets per day.
GFR 10-50 m L/min: administer with caution, consider dose reduction of 25-50%; GFR <10 m L/min: reduce dose by 50% and extend dosing interval.
Contraindicated in severe hepatic impairment (Child-Pugh C). For moderate impairment (Child-Pugh B), reduce dose by 50% and monitor; maximum 6 tablets per day. Mild impairment (Child-Pugh A): no adjustment but monitor.
Child-Pugh class A: no adjustment needed; Child-Pugh class B: reduce dose by 50%; Child-Pugh class C: reduce dose by 75%.
Not recommended for pediatric patients under 18 years of age.
Initial IV bolus of 5-20 mcg/kg; maintenance infusion of 0.5-2 mcg/kg/min. For neonates, reduce dose by 30-50% due to immature clearance.
Initiate with lowest dose (1 tablet every 6 hours as needed); do not exceed 6 tablets per day; monitor for respiratory depression, falls, and cognitive impairment.
Reduce initial IV bolus by 30-50% to 3-10 mcg/kg; titrate carefully; monitor for prolonged sedation and respiratory depression.
Addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion; risks from concomitant use with benzodiazepines or other CNS depressants; neonatal opioid withdrawal syndrome; and risks associated with use of acetaminophen (hepatotoxicity).
Risk of respiratory depression: Alfentanil can cause severe, life-threatening, or fatal respiratory depression. Monitor for respiratory depression, especially during initiation or following dose increases. Accidental ingestion of even one dose can be fatal. Concomitant use with central nervous system depressants (e.g., benzodiazepines, alcohol) may increase risk. Alfentanil is an opioid agonist and a Schedule II controlled substance with high potential for abuse and addiction.
Life-threatening respiratory depression,Addiction, abuse, and misuse,Risks from concomitant use with benzodiazepines or other CNS depressants,Neonatal opioid withdrawal syndrome,Hepatotoxicity from acetaminophen,Severe hypotension,Gastrointestinal adverse reactions (e.g., constipation, ileus),Seizures in patients with seizure disorders,Adrenal insufficiency,Risks in patients with head injury or increased intracranial pressure
Respiratory depression: Potentially fatal; monitor oxygenation and ventilation.,Abuse potential: Schedule II controlled substance; risk of addiction, abuse, and diversion.,Concomitant use with CNS depressants: Increases risk of profound sedation, respiratory depression, coma, and death; limit use or monitor closely.,Geriatric and cachectic patients: Increased sensitivity; reduce initial dose.,Hepatic impairment: Alfentanil clearance is reduced in patients with cirrhosis; consider dose adjustment.,Bradycardia and hypotension: Use with caution in patients with hypovolemia or reduced cardiac reserve.,Serotonin syndrome: Risk with concurrent serotonergic drugs (e.g., MAOIs, SSRIs, triptans); monitor for symptoms.,Withdrawal: Prolonged use may lead to physical dependence; taper dose gradually.
Significant respiratory depression,Acute or severe bronchial asthma in an unmonitored setting or without resuscitative equipment,Known or suspected gastrointestinal obstruction (e.g., paralytic ileus),Hypersensitivity to hydrocodone, acetaminophen, or any component of the formulation,Severe hepatic impairment (acetaminophen component)
Hypersensitivity to alfentanil, fentanyl, or any opioid,Significant respiratory depression (e.g., acute asthma, COPD in acute exacerbation),Acute or severe bronchial asthma,Suspected or known paralytic ileus,MAO inhibitor use within 14 days (serotonin syndrome risk),Myasthenia gravis (relative contraindication due to risk of respiratory muscle weakness),Morbid obesity with sleep apnea (relative contraindication; increased risk of respiratory depression)
Avoid alcohol. Grapefruit juice may alter metabolism via CYP3A4 inhibition; consider limiting intake. High-fat meals can increase absorption of benzhydrocodone; take consistently with or without food to maintain effect.
No significant food interactions known. Avoid grapefruit and grapefruit juice as they may inhibit CYP3A4 metabolism, potentially prolonging effects.
Apadaz (benzhydrocodone/acetaminophen) is a combination opioid/acetaminophen product. Opioid use during pregnancy may cause neonatal opioid withdrawal syndrome (NOWS) with prolonged use; risk is highest in third trimester. Acetaminophen is not teratogenic at therapeutic doses. FDA Pregnancy Category C (prior to 2019 labeling); current labeling advises use only if potential benefit justifies potential risk to fetus. First trimester: limited data; opioid use associated with neural tube defects in some studies, but confounding by maternal factors. Second trimester: no specific malformation risk. Third trimester: risk of NOWS, preterm labor, and intrauterine growth restriction with chronic use. Avoid prolonged use; acute use at standard doses is not associated with major teratogenic risk.
Alfentanil is an opioid analgesic; limited human data. No clear evidence of major malformations, but third trimester use may cause neonatal opioid withdrawal syndrome (NOWS). Avoid prolonged use or high doses near term; use during labor may cause respiratory depression in neonate.
Benzhydrocodone is a prodrug of hydrocodone; both hydrocodone and acetaminophen are excreted into breast milk. Hydrocodone M/P ratio is approximately 2.0 (milk:plasma concentration ratio). Acetaminophen M/P ratio is approximately 1.0. Low absolute infant dose; relative infant dose is about 2-4% of maternal weight-adjusted dose for hydrocodone and 10-20% for acetaminophen. AAP considers acetaminophen compatible with breastfeeding. Opioids should be used with caution; monitor infant for sedation, respiratory depression, and poor feeding. Avoid in mothers with CYP2D6 ultra-rapid metabolizer phenotype due to risk of increased morphine conversion.
Alfentanil is excreted into breast milk in very low concentrations; estimated relative infant dose is low (<2% of maternal weight-adjusted dose). M/P ratio not determined in humans. Compatible with breastfeeding with caution; monitor infant for drowsiness, feeding difficulties.
Pharmacokinetic changes in pregnancy (increased plasma volume, hepatic enzyme induction, altered opioid clearance): For acute pain, use lowest effective dose for shortest duration. Consider dose reduction postpartum as metabolic changes resolve. No specific dose adjustment guidelines for Apadaz; clinical judgment for opioid dose titration needed. Monitor for inadequate analgesia or withdrawal due to increased clearance. For chronic pain, consider tapering or alternative non-opioid therapy.
Pregnancy can alter alfentanil pharmacokinetics: increased volume of distribution, decreased plasma clearance, prolonged elimination half-life. Dose reduction may be needed for prolonged use; titrate to effect. During labor, use smallest effective dose.
Contains benzhydrocodone, a prodrug of hydrocodone, and acetaminophen. Abuse-deterrent properties due to enzymatic activation required in GI tract; consider in patients with risk of opioid misuse. Monitor for acetaminophen hepatotoxicity; max daily acetaminophen dose from all sources should not exceed 4 g. Avoid in severe hepatic impairment. Onset of analgesia is slower than immediate-release hydrocodone due to prodrug conversion.
Alfentanil is a potent, short-acting synthetic opioid (4-5 times more potent than fentanyl) with rapid onset (1-2 min) and brief duration (5-10 min). Primarily used for induction and maintenance of anesthesia, especially in short procedures. Requires careful monitoring of respiratory depression and chest wall rigidity, particularly during rapid IV administration. Hepatic metabolism (CYP3A4) affected by liver disease; reduce dose. Decrease dose in elderly and hypovolemic patients. Not recommended for chronic pain due to short half-life.
Take exactly as prescribed; do not crush, chew, or dissolve tablets as this can cause rapid release and overdose.,Avoid alcohol and other CNS depressants; may cause severe drowsiness, respiratory depression, or coma.,Do not take other acetaminophen-containing products; check labels for acetaminophen (APAP) to prevent liver damage.,Store securely and dispose of unused medication via take-back programs; prevent misuse by others.,Common side effects include nausea, constipation, dizziness, and drowsiness; contact prescriber if severe or persistent.
This medication causes drowsiness and dizziness; avoid driving or operating machinery for at least 24 hours after administration.,Report any difficulty breathing, chest tightness, or feeling faint immediately.,Alfentanil is used only in hospital settings under direct supervision of healthcare professionals.,Inform your doctor if you have a history of liver disease, lung disease, or drug/alcohol abuse.,Do not consume alcohol or other sedatives while under the effects of alfentanil.
No interactions on record
"Propantheline, an anticholinergic agent, can competitively antagonize muscarinic acetylcholine receptors, potentially reducing gastrointestinal motility and secretion. Alfentanil, a mu-opioid receptor agonist, also decreases gastrointestinal motility through central and peripheral opioid receptors. Concomitant use may synergistically inhibit peristalsis, leading to severe constipation, paralytic ileus, or delayed gastric emptying, which can increase the risk of aspiration and complicate anesthesia recovery."
"Alfentanil, a potent opioid analgesic, can cause significant hypotension and respiratory depression. When combined with furosemide, a loop diuretic that reduces blood volume and vascular resistance, there is a synergistic decrease in blood pressure, which may precipitate cardiovascular collapse, especially in patients with compromised circulatory reserves. Additionally, furosemide may enhance the sedative and respiratory depressant effects of alfentanil, leading to increased risk of respiratory acidosis and altered mental status."
"Alfentanil, a potent mu-opioid receptor agonist, can enhance the bradycardic effects of nebivolol, a beta-1 selective blocker with additional nitric oxide-mediated vasodilation. The combination may lead to excessive slowing of heart rate, reduced cardiac output, and potential hemodynamic instability, particularly in patients with underlying cardiac conduction abnormalities or hypovolemia."
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about APADAZ vs ALFENTANIL, answered by our medical review team.
APADAZ is a Opioid Analgesic that works by APADAZ is a combination of benzhydrocodone, a prodrug of hydrocodone, and acetaminophen. Hydrocodone acts as a full mu-opioid receptor agonist, inhibiting ascending pain pathways and altering pain perception. Acetaminophen's mechanism involves inhibition of cyclooxygenase (COX) enzymes, particularly in the CNS, and modulation of serotonergic pathways, contributing to analgesia and antipyresis.. ALFENTANIL is a Opioid Analgesic that works by Alfentanil is a potent, short-acting synthetic opioid analgesic that primarily acts as a mu-opioid receptor agonist. It binds to mu-opioid receptors in the central nervous system, leading to G-protein coupled activation of inwardly rectifying potassium channels and inhibition of voltage-gated calcium channels, resulting in hyperpolarization and reduced neurotransmitter release. This produces analgesia, sedation, and respiratory depression.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between APADAZ and ALFENTANIL depend on the specific clinical indication. These are both Opioid Analgesic agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of APADAZ is: Each tablet contains benzhydrocodone 4.08 mg (hydrocodone 3.33 mg) and acetaminophen 325 mg. One to 2 tablets every 4 to 6 hours as needed for pain; maximum 12 tablets per 24 hours.. The standard adult dose of ALFENTANIL is: Initial IV bolus of 5-20 mcg/kg; maintenance infusion of 0.5-1.5 mcg/kg/min; incremental boluses of 5-10 mcg/kg as needed. Induction of anesthesia: 50-100 mcg/kg IV.. 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 APADAZ and ALFENTANIL 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. APADAZ is classified as Category C. Apadaz (benzhydrocodone/acetaminophen) is a combination opioid/acetaminophen product. Opioid use during pregnancy may cause neonatal opioid withdrawal syndrome (NOWS) with prolonge. ALFENTANIL is classified as Category C. Alfentanil is an opioid analgesic; limited human data. No clear evidence of major malformations, but third trimester use may cause neonatal opioid withdrawal syndrome (NOWS). Avoid. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.