Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
DURAGESIC-100 vs ALFENTA
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Pure opioid agonist that binds to mu-opioid receptors in the CNS, mimicking endogenous endorphins to inhibit pain transmission. Also interacts with kappa and delta receptors. Therapeutic effects include analgesia, sedation, and euphoria.
μ-opioid receptor agonist that activates G-protein coupled receptors to inhibit adenylate cyclase, decreasing c AMP production, leading to reduced neuronal excitability and pain transmission.
Management of pain severe enough to require daily, around-the-clock, long-term opioid treatment in opioid-tolerant patients,Off-label: Chronic pain in non-opioid-tolerant patients (not recommended due to risk of respiratory depression)
Induction and maintenance of anesthesia,Analgesic supplement during surgical procedures,Intravenous use for monitored anesthesia care (MAC)
Transdermal patch; initial dose based on prior opioid use: for opioid-naive patients, 12 mcg/h every 72 hours; for opioid-tolerant patients, convert using equianalgesic tables; maximum dose 100 mcg/h per patch; apply to non-irritated, non-irradiated skin on chest, back, flank, or upper arm.
Intravenous: Initial dose 8-20 mcg/kg (0.5-1 min) then 0.5-3 mcg/kg/min or 3-5 mcg/kg q5-20min. For short procedures: 8-20 mcg/kg. For longer procedures: 50-75 mcg/kg followed by 0.5-3 mcg/kg/min.
Terminal elimination half-life approximately 20–27 hours after transdermal system removal (range 13–25 hours in healthy adults; prolonged in elderly, hepatic impairment, and cachexia).
Terminal elimination half-life: 90–111 minutes (1.5–1.85 hours); prolonged in hepatic impairment.
Primarily metabolized by CYP3A4 isoenzyme to norfentanyl and other inactive metabolites. Minor pathways via CYP3A5. First-pass metabolism is extensive after oral administration, but transdermal delivery bypasses this.
Hepatic via CYP3A4 to inactive metabolites; major metabolite is desmethylalfentanil (inactive).
Renal (primarily as metabolites, <10% unchanged fentanyl); fecal (about 9% of dose).
Primarily renal (urinary) elimination as metabolites; approximately 80% recovered in urine, 20% in feces.
Approximately 80–85% bound, primarily to alpha-1-acid glycoprotein (AAG) and albumin; increased free fraction in hypoalbuminemia.
Approximately 92% bound, primarily to alpha-1 acid glycoprotein and albumin.
3–8 L/kg (mean ~6 L/kg), indicating extensive tissue distribution (including deep compartments such as muscle and fat).
0.5–1.0 L/kg; reflects moderate tissue distribution; higher Vd in neonates and elderly.
Transdermal: approximately 92% of the dose over 72 hours (systemic absorption fraction).
Intravenous: 100%; intramuscular: approximately 90%; intrathecal: approximately 10% (due to systemic absorption following spinal administration).
GFR 30-60 m L/min: no adjustment required; GFR <30 m L/min: reduce dose by 50% and titrate cautiously; hemodialysis: not removed, avoid use or use with extreme caution.
No specific dose adjustment is recommended for renal impairment; however, alfentanil is primarily metabolized in the liver and its pharmacokinetics are not significantly altered in renal failure.
Child-Pugh class A: no adjustment; Child-Pugh class B: reduce initial dose by 50% and titrate slowly; Child-Pugh class C: avoid use or reduce dose by 75% with careful monitoring.
In hepatic impairment (Child-Pugh class A, B, C): Reduce dose by 50% and titrate carefully due to prolonged elimination half-life. Consider lower initial doses and extended dosing intervals.
For children ≥2 years old: initial dose 25 mcg/h for opioid-tolerant patients; for opioid-naive, use alternative analgesic; titrate in 12-25 mcg/h increments every 72 hours; do not use in children <2 years.
Children (1-12 years): Induction of anesthesia: 10-20 mcg/kg IV; maintenance: 5-10 mcg/kg IV or infusion 0.5-1 mcg/kg/min. For neonates and infants: Dose individualization required; titrate to effect.
Start at lowest available strength (12 mcg/h) and titrate slowly; monitor for respiratory depression, constipation, and cognitive effects; consider increased sensitivity to opioid effects.
Elderly patients (>65 years): Reduce initial dose by 30-50% and administer slowly. Due to decreased clearance and increased sensitivity, lower infusion rates (e.g., 0.3-0.5 mcg/kg/min) may be needed.
Risk of respiratory depression, especially in non-opioid-tolerant patients; risk of accidental exposure leading to fatal overdose; contraindicated in acute or postoperative pain; risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy; risk of interaction with CYP3A4 inhibitors leading to fatal respiratory depression; risk of death from concomitant use with benzodiazepines or CNS depressants.
Risk of respiratory depression, particularly in elderly or debilitated patients. Concomitant use with benzodiazepines or other CNS depressants may cause profound sedation, respiratory depression, coma, and death.
Life-threatening respiratory depression: monitor closely, especially during initiation and dose escalation,Accidental exposure: can cause fatal overdose in children; apply patch to dry, non-irritated skin on flat surface of upper torso,Neonatal opioid withdrawal syndrome: prolonged use during pregnancy can result in withdrawal in newborns,Risks from concomitant use with benzodiazepines or CNS depressants: additive sedation and respiratory depression,Risk of hypotension, bradycardia, and seizure in patients with compromised cardiovascular or cerebrovascular function,Serotonin syndrome when co-administered with serotonergic drugs,Adrenal insufficiency and androgen deficiency with long-term use,Severe hypotension in patients with reduced blood volume or concurrent drug therapy that compromises vasomotor tone,Biliary tract spasm and increased intracholedochal pressure,Avoid in patients with head injury, increased intracranial pressure, or impaired consciousness,Do not cut, chew, or swallow patch; apply patch immediately after removal from package; wear time 72 hours,Fever or external heat can increase absorption; avoid exposing application site to direct heat sources
Respiratory depression; abuse potential; hypotension; bradycardia; muscle rigidity; serotonin syndrome with concurrent serotonergic drugs; adrenal insufficiency; risk of withdrawal with prolonged use.
Hypersensitivity to fentanyl or any component of the patch,Significant respiratory depression,Acute or severe bronchial asthma in an unmonitored setting or in the absence of resuscitative equipment,Known or suspected paralytic ileus,Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days of stopping an MAOI,Non-opioid-tolerant patients: contraindicated for acute pain, postoperative pain, mild/intermittent pain, or pain that can be managed by non-opioid analgesics,Pregnancy: prolonged use can cause neonatal opioid withdrawal syndrome,Lactation: fentanyl is excreted in breast milk; use caution
Hypersensitivity to alfentanil or any component; significant respiratory insufficiency; severe asthma; paralytic ileus; concurrent use of MAOIs (or within 14 days); acute or postoperative pain management in children (except for procedural sedation).
Avoid grapefruit and grapefruit juice during therapy, as they can affect liver enzymes and alter fentanyl metabolism. No other specific food restrictions. However, a high-fat meal may delay absorption of oral fentanyl but this is not relevant for transdermal formulation. Maintain caution with alcohol intake as it can potentiate CNS depression.
No known interactions with food. However, grapefruit juice may increase alfentanil serum concentrations due to CYP3A4 inhibition; avoid concurrent consumption.
First trimester: Data insufficient to establish specific risk; fentanyl crosses placenta. Second/third trimester: Chronic use may cause neonatal opioid withdrawal syndrome (NOWS). Use not recommended unless benefit outweighs risk.
Alfentanil, a short-acting opioid analgesic, is classified as FDA Pregnancy Category C. No well-controlled studies in pregnant women exist. In animal studies, no teratogenic effects were observed at clinically relevant doses; however, high doses caused embryotoxicity and increased fetal mortality. Trimester-specific risks: First trimester - potential for minor malformations based on limited human data; second trimester - possible risk if used chronically; third trimester - prolonged use may lead to neonatal respiratory depression, withdrawal syndrome, or opioid dependence. Use only if benefits outweigh risks.
Fentanyl excreted in breast milk; M/P ratio approximately 0.5. Limited data suggest low levels, but monitoring for infant sedation and respiratory depression recommended. Avoid use or use with caution.
Alfentanil is excreted into human breast milk in low concentrations. The milk-to-plasma (M/P) ratio is approximately 0.3. Estimated infant dose is <1% of maternal weight-adjusted dose, which is considered clinically insignificant. However, due to potential for neonatal opioid effects, caution is advised; monitor infant for drowsiness, respiratory depression, and feeding difficulties. Consider alternative analgesics with established safety profiles, such as acetaminophen or ibuprofen, for lactation.
Increased clearance during pregnancy may require dose adjustment; no specific guidelines. Close monitoring for efficacy and withdrawal; taper to avoid NOWS.
Pregnancy can alter pharmacokinetics of alfentanil. Increased plasma volume and distribution may require higher doses to achieve same effect, while decreased plasma protein binding may increase free fraction, potentiating effects. Alpha-1-acid glycoprotein levels change in pregnancy, affecting binding. In third trimester, clearance may be increased by up to 50% due to enhanced hepatic metabolism. Therefore, dose adjustments may be needed: consider starting at low dose and titrating to effect, with close monitoring. For intravenous administration, typical adult doses (5-20 μg/kg) may need adjustments; no standard pregnancy-specific dosing exists. Use the lowest effective dose for the shortest duration. In labor, avoid high doses prior to delivery due to risk of neonatal respiratory depression.
Duragesic-100 is a transdermal fentanyl patch delivering 100 mcg/h. Use only in opioid-tolerant patients due to risk of respiratory depression. Do not cut or damage the patch; apply to non-irritated, non-hairy skin on upper torso. Avoid heat sources (heating pads, saunas) as increased temperature can accelerate drug absorption, leading to fatal overdose. Monitor for signs of serotonin syndrome when co-administered with serotonergic drugs. Rotate application sites to minimize skin irritation.
Alfentanil is a potent, rapid-onset, short-acting opioid analgesic used primarily for induction and maintenance of anesthesia. Due to its high protein binding (90%) and rapid redistribution, it has a shorter duration of action than fentanyl, making it suitable for brief, painful procedures. It undergoes hepatic metabolism via CYP3A4, so concomitant use with CYP3A4 inhibitors like ketoconazole or erythromycin can prolong its effects. Use caution in elderly or hypovolemic patients due to increased risk of hypotension. Naloxone reverses respiratory depression. Alfentanil is 5-10 times less potent than fentanyl.
Apply the patch to clean, dry, hairless skin on the chest, back, or upper arm. Do not shave the area; clip hair if necessary.,Do not cut, tear, or damage the patch. Use only as directed by your healthcare provider.,Avoid exposing the patch to direct heat sources such as heating pads, electric blankets, hot tubs, or prolonged sunbathing, as this can increase the amount of medicine absorbed and cause a fatal overdose.,Keep the patch away from children and pets, as exposure can be fatal. Dispose of used patches by folding them in half and flushing down the toilet or placing in a sealed container.,Do not stop using this medication suddenly without consulting your doctor, as withdrawal symptoms may occur.,Seek emergency help if you experience slow/shallow breathing, difficulty waking up, or extreme drowsiness.,Do not drink alcohol while using this medication, as it may increase the risk of serious side effects.
This medication is given only by a healthcare professional in a hospital or surgical setting.,You may feel drowsy, dizzy, or nauseated after receiving this drug.,Report any difficulty breathing or slow heart rate to your healthcare provider immediately.,Avoid alcohol and sedatives for 24 hours after administration, as they can increase side effects.,Do not drive or operate machinery until the effects have fully worn off.
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 DURAGESIC-100 vs ALFENTA, answered by our medical review team.
DURAGESIC-100 is a Opioid Analgesic that works by Pure opioid agonist that binds to mu-opioid receptors in the CNS, mimicking endogenous endorphins to inhibit pain transmission. Also interacts with kappa and delta receptors. Therapeutic effects include analgesia, sedation, and euphoria.. ALFENTA is a Opioid Analgesic that works by μ-opioid receptor agonist that activates G-protein coupled receptors to inhibit adenylate cyclase, decreasing c AMP production, leading to reduced neuronal excitability and pain transmission.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between DURAGESIC-100 and ALFENTA 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 DURAGESIC-100 is: Transdermal patch; initial dose based on prior opioid use: for opioid-naive patients, 12 mcg/h every 72 hours; for opioid-tolerant patients, convert using equianalgesic tables; maximum dose 100 mcg/h per patch; apply to non-irritated, non-irradiated skin on chest, back, flank, or upper arm.. The standard adult dose of ALFENTA is: Intravenous: Initial dose 8-20 mcg/kg (0.5-1 min) then 0.5-3 mcg/kg/min or 3-5 mcg/kg q5-20min. For short procedures: 8-20 mcg/kg. For longer procedures: 50-75 mcg/kg followed by 0.5-3 mcg/kg/min.. 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 DURAGESIC-100 and ALFENTA 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. DURAGESIC-100 is classified as Category C. First trimester: Data insufficient to establish specific risk; fentanyl crosses placenta. Second/third trimester: Chronic use may cause neonatal opioid withdrawal syndrome (NOWS). . ALFENTA is classified as Category C. Alfentanil, a short-acting opioid analgesic, is classified as FDA Pregnancy Category C. No well-controlled studies in pregnant women exist. In animal studies, no teratogenic effect. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.