Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
DURAGESIC-75 vs ALFENTA
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Fentanyl is a potent opioid agonist primarily at the mu-opioid receptor, exerting its analgesic effects by mimicking endogenous endorphins and enkephalins to activate G-protein-coupled inwardly rectifying potassium channels, leading to hyperpolarization and reduced neuronal excitability in pain pathways.
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 and for which alternative treatment options are inadequate (FDA-approved for opioid-tolerant patients only).
Induction and maintenance of anesthesia,Analgesic supplement during surgical procedures,Intravenous use for monitored anesthesia care (MAC)
Adults: Apply one 75 mcg/hr transdermal patch every 72 hours. Start with lower dose in opioid-naive patients.
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.
22-25 hours after removal of patch; increased in elderly, hepatic/renal impairment
Terminal elimination half-life: 90–111 minutes (1.5–1.85 hours); prolonged in hepatic impairment.
Primarily metabolized via CYP3A4 in the liver and intestinal mucosa to norfentanyl and other minor metabolites; undergoes extensive first-pass metabolism.
Hepatic via CYP3A4 to inactive metabolites; major metabolite is desmethylalfentanil (inactive).
Renal (75% as metabolites, <10% unchanged), fecal (25%)
Primarily renal (urinary) elimination as metabolites; approximately 80% recovered in urine, 20% in feces.
90-95% bound to alpha-1-acid glycoprotein and albumin
Approximately 92% bound, primarily to alpha-1 acid glycoprotein and albumin.
6-7 L/kg, indicating extensive tissue distribution
0.5–1.0 L/kg; reflects moderate tissue distribution; higher Vd in neonates and elderly.
Fentanyl transdermal: 50-65% of patch content absorbed into systemic circulation
Intravenous: 100%; intramuscular: approximately 90%; intrathecal: approximately 10% (due to systemic absorption following spinal administration).
GFR 30-89 m L/min: No adjustment. GFR <30 m L/min: Reduce dose by 50% and monitor.
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. Class B: Reduce dose by 25-50%. Class C: Avoid use.
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.
Children ≥2 years: 12.5-25 mcg/hr initial, titrate based on need; max dose 25 mcg/hr for opioid-naive.
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.
Initial dose reduction of 25-50%; titrate cautiously; avoid in frail elderly.
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 that may result in death; ensure proper patient selection, dosing, and monitoring. Avoid use in opioid non-tolerant patients. Accidental exposure can be fatal. Concomitant use with CNS depressants increases risk. Risk of abuse, misuse, addiction, and diversion. Neonatal opioid withdrawal syndrome with prolonged use during pregnancy. Risk of life-threatening respiratory depression from CYP3A4 inhibitors or discontinuation of CYP3A4 inducers.
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.
Risk of life-threatening respiratory depression, especially in elderly, cachectic, or debilitated patients,Risk of opioid-induced hyperalgesia,Risk of serotonin syndrome with serotonergic drugs,Hypersensitivity reactions including anaphylaxis,Risk of withdrawal with abrupt discontinuation,Hepatic or renal impairment may alter pharmacokinetics,Avoid in patients with significant respiratory depression, acute or severe bronchial asthma, or known or suspected paralytic ileus,May impair mental or physical abilities needed for driving or operating machinery,Use with caution in patients with head injuries, increased intracranial pressure, or convulsive disorders,Application site reactions or adhesive-related injuries
Respiratory depression; abuse potential; hypotension; bradycardia; muscle rigidity; serotonin syndrome with concurrent serotonergic drugs; adrenal insufficiency; risk of withdrawal with prolonged use.
Opioid non-tolerant patients (not established for acute pain or short-term use),Significant respiratory depression,Acute or severe bronchial asthma in an unmonitored setting or without resuscitative equipment,Known or suspected gastrointestinal obstruction, including paralytic ileus,Hypersensitivity to fentanyl or any component of the system (e.g., adhesives),Concurrent use of monoamine oxidase inhibitors (MAOIs) or within 14 days of such therapy
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).
No significant food interactions. Grapefruit juice may increase fentanyl levels via CYP3A4 inhibition; caution with high intake. Avoid alcohol due to additive CNS depression.
No known interactions with food. However, grapefruit juice may increase alfentanil serum concentrations due to CYP3A4 inhibition; avoid concurrent consumption.
Fetal risk cannot be ruled out. In first trimester, no clear evidence of major malformations from opioid analgesics, but data limited. Second and third trimesters: chronic use may cause fetal opioid dependence, neonatal abstinence syndrome (NAS) postpartum. Use during labor may cause respiratory depression in neonate. Risk of preterm birth and low birth weight with prolonged use.
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 is excreted in breast milk. M/P ratio approximately 0.4. Breastfeeding is generally not recommended during Duragesic-75 use due to risk of infant sedation and respiratory depression. If used, monitor infant for unusual sleepiness, difficulty breathing, or poor feeding. Alternative analgesics are preferred.
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.
No specific dose adjustments are established for Duragesic-75 in pregnancy. Fentanyl pharmacokinetics may be altered due to increased plasma volume, renal clearance, and hepatic metabolism; however, transdermal absorption may be inconsistent. Use lowest effective dose for shortest duration. Consider alternative opioids with more pregnancy data. Taper dose before delivery to reduce NAS risk.
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-75 delivers fentanyl at 75 mcg/hour transdermally. Do not use in opioid-naive patients due to risk of fatal respiratory depression. Apply to non-irritated, non-hairy skin on upper torso or upper arm. Avoid heat sources (heating pads, hot tubs) as heat increases absorption. Onset ~12-24 hours; peak effect ~24-72 hours. Remove old patch before applying new; rotate sites. Do not cut or damage the patch. Monitor for serotonin syndrome if used with serotonergic drugs. For breakthrough pain, use immediate-release opioids not additional fentanyl patches.
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 a flat, non-hairy area of the upper body or arm. Do not use on skin that is irritated, cut, or scarred.,Do not expose the patch to direct heat sources like heating pads, electric blankets, hot tubs, or sunbathing—this can cause a dangerous overdose.,Wash hands after handling the patch. Dispose of used patches by folding sticky sides together and flushing down toilet per FDA guidelines.,Remove the old patch and apply the new patch to a different skin site every 72 hours (3 days). Rotate sites to avoid skin irritation.,Do not cut, chew, or damage the patch—this can lead to rapid release of fentanyl and fatal overdose.,Store patches in a secure place away from children and pets. Accidental exposure can be fatal.,Common side effects include nausea, vomiting, constipation, dizziness, and drowsiness. Report severe drowsiness, confusion, difficulty breathing, or signs of an allergic reaction.,Avoid alcohol, other opioids, benzodiazepines, and sedatives as they increase risk of respiratory depression.,Do not stop using this medication suddenly; taper with prescriber to avoid withdrawal symptoms.,Seek emergency care for symptoms of overdose: slow or shallow breathing, extreme drowsiness, or unresponsiveness.
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-75 vs ALFENTA, answered by our medical review team.
DURAGESIC-75 is a Opioid Analgesic that works by Fentanyl is a potent opioid agonist primarily at the mu-opioid receptor, exerting its analgesic effects by mimicking endogenous endorphins and enkephalins to activate G-protein-coupled inwardly rectifying potassium channels, leading to hyperpolarization and reduced neuronal excitability in pain pathways.. 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-75 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-75 is: Adults: Apply one 75 mcg/hr transdermal patch every 72 hours. Start with lower dose in opioid-naive patients.. 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-75 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-75 is classified as Category C. Fetal risk cannot be ruled out. In first trimester, no clear evidence of major malformations from opioid analgesics, but data limited. Second and third trimesters: chronic use may . 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.