Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
ERYC 125 vs ACTIQ
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Erythromycin binds to the 50S subunit of bacterial ribosomes, inhibiting protein synthesis by blocking translocation of peptidyl-t RNA. It also activates motilin receptors in the gastrointestinal tract, enhancing gastric motility.
Opioid agonist; binds to mu-opioid receptors in the CNS, altering pain perception and response.
Treatment of infections caused by susceptible strains of microorganisms (e.g., respiratory tract infections, skin infections, pertussis, diphtheria, syphilis),Off-label: Prokinetic agent for gastroparesis, treatment of delayed gastric emptying
Management of breakthrough pain in cancer patients aged 16 and older who are already receiving and tolerant to opioid therapy for their underlying persistent cancer pain
250 mg orally every 6 hours or 500 mg every 12 hours; maximum 4 g/day.
200 mcg transmucosally, titrated upward as needed; initial dose for opioid-tolerant patients is 200 mcg, with additional doses possible after 15 minutes if needed. Maximum 4 doses per episode. At least 4 hours between episodes.
1.5-2.0 hours in adults; prolonged in hepatic impairment (up to 5-6 hours) or neonates.
Terminal half-life 0.83–2 hours (mean 1.3 h) in adults; note that context: transmucosal absorption leads to rapid onset but short duration; half-life is not correlated with clinical effect due to oral transmucosal route and rapid redistribution.
Primarily hepatic via cytochrome P450 3A4 (CYP3A4) isoenzyme; undergoes demethylation and hydrolysis; major metabolite is desosamine.
Primarily hepatic via CYP3A4 to inactive metabolites (norfentanyl, despropionylfentanyl, hydroxyfentanyl) and other metabolites; <7% excreted unchanged in urine.
Primarily hepatic metabolism; ~2-5% excreted unchanged in urine, ~15-20% in bile/feces as active drug.
Primarily renal as metabolites (about 75% as metabolites, <10% unchanged). Fecal excretion accounts for <9%. Biliary excretion is minor.
70-90% bound to albumin and alpha-1-acid glycoprotein.
Fentanyl is 80–85% bound to plasma proteins (primarily albumin and α1-acid glycoprotein).
0.5-0.9 L/kg; indicates distribution into total body water with some tissue binding.
Approximately 4 L/kg (range 3–6 L/kg); large Vd indicates extensive tissue distribution and redistribution contributing to short duration.
Oral: ~35% (acid-labile, enteric-coated).
Oral transmucosal: 50% (range 47–54%) relative to IV; variable and enhanced by rapid absorption through buccal mucosa.
No dose adjustment required for GFR >10 m L/min. For GFR <10 m L/min, reduce dose by 50% or extend interval to every 8-12 hours.
No specific GFR-based dose adjustment recommended; use with caution in severe renal impairment (Cr Cl < 30 m L/min) and consider dose reduction due to potential accumulation.
Child-Pugh Class A: no adjustment. Class B: reduce dose by 50%. Class C: reduce dose by 75% or avoid use.
Child-Pugh Class A/B: No adjustment. Child-Pugh Class C: Reduce initial dose to 100 mcg and titrate slowly; monitor closely for prolonged effects.
30-50 mg/kg/day orally divided every 6-8 hours; maximum 2 g/day.
Not approved for pediatric use; safety and efficacy not established in patients under 16 years.
No specific adjustment; monitor for ototoxicity and QT prolongation; consider lower initial dose due to age-related renal decline.
Initiate at 100 mcg transmucosally; titrate slowly due to increased sensitivity and risk of respiratory depression. Monitor for adverse effects.
No FDA boxed warning for ERYC 125.
Risk of respiratory depression, addiction, abuse, and misuse; accidental ingestion can be fatal; concomitant use with benzodiazepines or CNS depressants may cause profound sedation, respiratory depression, coma, and death; not for use in opioid non-tolerant patients; risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy; serious, life-threatening, or fatal respiratory depression may occur even at recommended doses.
Risk of QT prolongation and ventricular arrhythmias (e.g., torsades de pointes), especially with other QT-prolonging drugs or electrolyte abnormalities,Hepatic impairment: monitor liver function,Potential for drug interactions via CYP3A4 inhibition,May exacerbate myasthenia gravis,Infantile hypertrophic pyloric stenosis (IHPS) risk in neonates
Risk of respiratory depression; addiction, abuse, and misuse; interactions with CNS depressants; serotonin syndrome; adrenal insufficiency; severe hypotension; seizures; withdrawal; use in patients with head injuries, increased intracranial pressure, biliary tract disease, pancreatitis; risk of choking with lozenge; oral mucosal irritation; dental caries; hypokalemia; hyponatremia; use in elderly, cachectic, or debilitated patients.
Hypersensitivity to erythromycin or any macrolide antibiotic,Concomitant use with CYP3A4 substrates that prolong QT interval (e.g., terfenadine, astemizole, cisapride, pimozide),Pre-existing QT prolongation or cardiac arrhythmia history
Significant respiratory depression; acute or severe bronchial asthma in an unmonitored setting or without resuscitative equipment; known or suspected paralytic ileus; hypersensitivity to fentanyl or any component; opioid non-tolerant patients; management of acute or postoperative pain including headache/migraine, dental pain, or emergency department use.
Grapefruit and grapefruit juice should be avoided as they can increase drug levels and risk of toxicity. Food does not significantly alter absorption of the ethylsuccinate formulation, but taking with a high-fat meal may slightly delay absorption. Avoid alcohol as it may increase risk of hepatotoxicity.
No significant food interactions. Grapefruit juice may increase fentanyl levels, but specific studies with ACTIQ are lacking. Avoid alcohol, as it may increase sedation and respiratory depression risk.
Erythromycin, including ERYC 125, has not been associated with major congenital malformations in human studies. However, there is a potential increased risk of pyloric stenosis in infants exposed in utero or postnatally. No known teratogenic effects in first trimester; use in pregnancy is generally considered safe when indicated, especially for infections like chlamydia or syphilis.
FDA Pregnancy Category C. First trimester: limited human data; animal studies show increased resorptions and fetal growth restriction. Second/third trimester: chronic use may cause neonatal opioid withdrawal syndrome; avoid use during labor due to risk of neonatal respiratory depression.
Erythromycin is excreted into breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 0.5. It is considered compatible with breastfeeding by the American Academy of Pediatrics, but may increase the risk of pyloric stenosis in neonates. Monitor for gastrointestinal symptoms in the infant.
Excreted in breast milk; M/P ratio not established. Limited data suggest low levels, but risk of infant sedation and respiratory depression. Avoid use while breastfeeding unless potential benefit outweighs risk.
No specific dose adjustment is required for pregnancy based on pharmacokinetic changes. However, erythromycin has reduced plasma concentrations in late pregnancy due to increased volume of distribution and clearance, but no dose adjustment is recommended. Standard dosing is used.
Due to increased plasma volume and hepatic metabolism in pregnancy, dose requirements may increase; adjust based on clinical response and tolerance. Avoid use during labor and delivery due to risk of neonatal respiratory depression; short-term use preferred.
ERYC 125 (erythromycin ethylsuccinate) is a macrolide antibiotic; note that it may prolong QT interval, especially when combined with other QT-prolonging drugs. Avoid use in patients with hepatic impairment or known cholestatic jaundice. Administer on an empty stomach (1 hour before or 2 hours after meals) for optimal absorption, but food does not significantly affect the ethylsuccinate formulation.
ACTIQ is a transmucosal immediate-release fentanyl formulation indicated for breakthrough cancer pain in opioid-tolerant patients. Initiate with the lowest strength (200 mcg) and titrate upward. Avoid use in opioid-naive patients due to risk of fatal respiratory depression. Place the unit between cheek and lower gum, not sublingually. Instruct patient not to bite or suck the unit. Monitor for sedation and respiratory depression. Multiple units may be used per episode if needed, but wait at least 4 hours before next episode. Dispose of partially used units by flushing down toilet.
Take exactly as prescribed; do not skip doses or stop early even if you feel better.,Take this medication on an empty stomach, at least 1 hour before or 2 hours after a meal.,Avoid grapefruit and grapefruit juice while taking this medicine.,Report any signs of liver problems: yellowing of skin/eyes, dark urine, severe stomach pain.,Notify your doctor immediately if you experience irregular heartbeat, fainting, or severe diarrhea.,Complete the full course to prevent antibiotic resistance.
Only use ACTIQ if you are already taking regular around-the-clock opioid pain medicine and are tolerant to opioids.,Do not use ACTIQ for short-term pain like after surgery, headache, or dental pain.,Place the unit in your cheek pouch, not under your tongue. Do not chew or suck it.,If you need more than 4 units per day, contact your doctor as your dose may need adjustment.,Store ACTIQ in a safe place away from children, as accidental ingestion can be fatal.,Dispose of unused or partially used units by flushing them down the toilet.
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 ERYC 125 vs ACTIQ, answered by our medical review team.
ERYC 125 is a Macrolide Antibiotic that works by Erythromycin binds to the 50S subunit of bacterial ribosomes, inhibiting protein synthesis by blocking translocation of peptidyl-t RNA. It also activates motilin receptors in the gastrointestinal tract, enhancing gastric motility.. ACTIQ is a Opioid Analgesic that works by Opioid agonist; binds to mu-opioid receptors in the CNS, altering pain perception and response.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between ERYC 125 and ACTIQ 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 ERYC 125 is: 250 mg orally every 6 hours or 500 mg every 12 hours; maximum 4 g/day.. The standard adult dose of ACTIQ is: 200 mcg transmucosally, titrated upward as needed; initial dose for opioid-tolerant patients is 200 mcg, with additional doses possible after 15 minutes if needed. Maximum 4 doses per episode. At least 4 hours between episodes.. 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 ERYC 125 and ACTIQ 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. ERYC 125 is classified as Category C. Erythromycin, including ERYC 125, has not been associated with major congenital malformations in human studies. However, there is a potential increased risk of pyloric stenosis in . ACTIQ is classified as Category C. FDA Pregnancy Category C. First trimester: limited human data; animal studies show increased resorptions and fetal growth restriction. Second/third trimester: chronic use may cause. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.