Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
OMTRYG vs ALFENTANIL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
OMTRYG is a combination of ombitasvir, paritaprevir, and ritonavir. Ombitasvir is an NS5A inhibitor that blocks viral RNA replication and assembly. Paritaprevir is an NS3/4A protease inhibitor that prevents viral polyprotein cleavage. Ritonavir is a CYP3A4 inhibitor used to boost paritaprevir levels.
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.
Treatment of chronic hepatitis C virus (HCV) genotype 4 infection without cirrhosis or with compensated cirrhosis,Treatment of chronic HCV genotype 1 infection (with ribavirin or as part of combination therapy)
Analgesic adjunct during general anesthesia,Induction of anesthesia,Maintenance of anesthesia for short surgical procedures,Off-label: Procedural sedation in monitored settings
2 mg orally twice daily; if taste disturbance occurs, reduce to 1 mg twice daily.
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 is 12-14 hours in healthy adults, allowing once-daily dosing. In renal impairment (Cr Cl <30 m L/min), half-life prolongs to 24-36 hours requiring dose adjustment.
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.
Ombitasvir: primarily metabolized by CYP3A4; Paritaprevir: primarily metabolized by CYP3A4; Ritonavir: primarily metabolized by CYP3A4 and to a lesser extent by CYP2D6.
Alfentanil is primarily metabolized by hepatic cytochrome P450 enzymes, mainly CYP3A4, through oxidative N-dealkylation and O-demethylation to inactive metabolites.
Primarily renal excretion unchanged (approximately 70%), with 30% metabolized hepatically and excreted in feces via bile. Renal clearance accounts for ~60% of total clearance.
Primarily hepatic metabolism via CYP3A4; <1% excreted unchanged in urine; metabolites (mainly noralfentanil) excreted renally. Biliary/fecal excretion of metabolites accounts for ~30%.
Approximately 95% bound to serum albumin.
~92% bound primarily to alpha-1-acid glycoprotein (AAG) and albumin.
0.3-0.5 L/kg, indicating distribution primarily in extracellular fluid and plasma with limited tissue penetration.
Vd: 0.4–1.0 L/kg (mean ~0.75 L/kg). Moderate Vd reflecting rapid distribution to tissues, especially brain and muscle.
Oral: 60-80% (first-pass effect); Subcutaneous: 90-100%.
IV: 100%. IM: ~90%. Epidural: ~30–50% due to local uptake and redistribution. No significant oral bioavailability.
No dose adjustment required for GFR ≥30 m L/min; avoid use if GFR <30 m L/min.
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.
No dose adjustment required for Child-Pugh A or B; not recommended in Child-Pugh C due to lack of data.
Child-Pugh class A: no adjustment needed; Child-Pugh class B: reduce dose by 50%; Child-Pugh class C: reduce dose by 75%.
Not approved for pediatric patients <18 years; safety and efficacy not established.
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.
No dose adjustment required based on age; monitor for taste disturbance and renal function.
Reduce initial IV bolus by 30-50% to 3-10 mcg/kg; titrate carefully; monitor for prolonged sedation and respiratory depression.
WARNING: HEPATITIS B VIRUS REACTIVATION — Test all patients for evidence of current or prior HBV infection before initiating treatment. HBV reactivation has been reported in patients coinfected with HCV and HBV, which can result in fulminant hepatitis, hepatic failure, and death.
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.
Risk of hepatitis B virus reactivation,Hepatic decompensation/hepatic failure in patients with cirrhosis,ALT elevations and hepatic injury,Risk of drug interactions (significant CYP3A4 inhibition),Use with ribavirin: ribavirin-related adverse effects (e.g., anemia, teratogenicity)
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.
Severe hepatic impairment (Child-Pugh C),Known hypersensitivity to ombitasvir, paritaprevir, ritonavir, or any component of the formulation,Coadministration with drugs highly dependent on CYP3A4 for clearance (e.g., alfuzosin, amiodarone, sildenafil when used for pulmonary arterial hypertension, ergot derivatives, lovastatin, simvastatin, midazolam, triazolam),Moderate to severe hepatic impairment in patients with cirrhosis (Child-Pugh B and C)
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)
No clinically significant food interactions reported.
No significant food interactions known. Avoid grapefruit and grapefruit juice as they may inhibit CYP3A4 metabolism, potentially prolonging effects.
Pregnancy Category X: contraindicated in pregnancy. First trimester: major congenital malformations (e.g., neural tube defects, cardiac anomalies). Second and third trimesters: fetal growth restriction, oligohydramnios, neonatal renal failure. Risk is dose-dependent.
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.
Contraindicated during breastfeeding. M/P ratio not established; drug excreted into breast milk. Potential for serious adverse effects in nursing infant (renal toxicity).
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.
Not applicable; contraindicated in pregnancy. No dose adjustment recommended due to contraindication.
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.
OMTRYG (triptorelin pamoate) is a Gn RH agonist used for advanced prostate cancer. Monitor for tumor flare at therapy initiation; consider antiandrogen coadministration for first month. Baseline and periodic serum testosterone and PSA levels are essential. Caution in patients with spinal cord compression or urinary tract obstruction. Risk of QT prolongation; assess electrolytes and ECG in at-risk patients. Depot formulation provides 6-month coverage.
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.
OMTRYG is injected every 6 months by a healthcare provider.,You may experience a temporary increase in bone pain or urinary symptoms during the first few weeks.,Report new or worsening pain, difficulty urinating, or leg weakness immediately.,Hot flashes, decreased libido, and erectile dysfunction are common.,Do not stop treatment without consulting your doctor.,Keep all scheduled injections; missed doses can reduce effectiveness.
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 OMTRYG vs ALFENTANIL, answered by our medical review team.
OMTRYG is a HMG-CoA Reductase Inhibitor (Statin) that works by OMTRYG is a combination of ombitasvir, paritaprevir, and ritonavir. Ombitasvir is an NS5A inhibitor that blocks viral RNA replication and assembly. Paritaprevir is an NS3/4A protease inhibitor that prevents viral polyprotein cleavage. Ritonavir is a CYP3A4 inhibitor used to boost paritaprevir levels.. 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 OMTRYG and ALFENTANIL 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 OMTRYG is: 2 mg orally twice daily; if taste disturbance occurs, reduce to 1 mg twice daily.. 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 OMTRYG 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. OMTRYG is classified as Category C. Pregnancy Category X: contraindicated in pregnancy. First trimester: major congenital malformations (e.g., neural tube defects, cardiac anomalies). Second and third trimesters: fet. 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.