Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
Amoxicillin-Clavulanate vs ABSTRAL
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Amoxicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation and autolysin inhibitors. Clavulanate is a beta-lactamase inhibitor that binds to and inactivates beta-lactamases, protecting amoxicillin from hydrolysis.
Fentanyl is a potent mu-opioid receptor agonist, producing analgesia and sedation by activating G-protein coupled opioid receptors in the central nervous system.
Acute bacterial sinusitis,Acute otitis media,Community-acquired pneumonia,Urinary tract infections,Skin and skin structure infections,Intra-abdominal infections,Lower respiratory tract infections,Diabetic foot infections,Prophylaxis of infection following surgery (off-label)
Management of breakthrough pain in cancer patients aged 18 and older who are already receiving and tolerant to around-the-clock opioid therapy for their underlying persistent cancer pain.
500 mg/125 mg orally every 8 hours or 875 mg/125 mg orally every 12 hours; intravenous: 1 g/0.2 g every 8 hours.
For breakthrough pain in opioid-tolerant patients: initial dose 100 mcg sublingual tablet, titrate across strengths (100, 200, 300, 400, 600, 800 mcg) as needed; maximum 2 doses per episode, minimum 2 hours between episodes.
Amoxicillin: ~1-1.3 hours in adults with normal renal function; Clavulanate: ~1 hour. Both prolonged in renal impairment (amoxicillin up to 7-20 hours with Cr Cl <10 m L/min).
Terminal elimination half-life: 6-10 hours (mean 8 hours); prolonged in elderly and hepatic impairment
Amoxicillin is partially metabolized via hydrolysis of the beta-lactam ring to inactive penicilloic acid, minor hepatic metabolism; excreted primarily unchanged renally. Clavulanate is extensively metabolized in the liver, primarily to metabolites excreted in urine and feces.
Hepatic metabolism primarily via CYP3A4; major metabolites include norfentanyl (inactive) and other minor metabolites.
Amoxicillin: ~60% renal as unchanged drug via glomerular filtration and tubular secretion; Clavulanate: ~30-50% renal as metabolites and unchanged, remainder fecal. Approximately 50-70% of total dose excreted renally within 6 hours.
Renal: ~70% as metabolites (primarily fentanyl conjugates and norfentanyl), ~10% unchanged; Fecal: ~9%; Biliary: minimal
Amoxicillin: ~17% bound to serum protein (primarily albumin); Clavulanate: ~25% bound to albumin.
80-85% bound primarily to albumin and alpha-1-acid glycoprotein
Amoxicillin: Vd ~0.3-0.4 L/kg; clavulanate: Vd ~0.3 L/kg. Distributes well into interstitial fluid, tissues, and bone; limited CNS penetration (10-20% of serum levels) unless inflamed meninges.
4-6 L/kg; large Vd indicates extensive tissue distribution
Oral: 80-90% for both components; food does not significantly affect absorption (note: clavulanate is better absorbed with food, extended-release tab with food).
Sublingual: 70-90% (mean 80%); buccal: 50-65%; oral: ~30% due to first-pass metabolism
Cr Cl 30-50 m L/min: 500 mg/125 mg orally every 12 hours; Cr Cl 10-29 m L/min: 500 mg/125 mg orally every 24 hours; Cr Cl <10 m L/min: 500 mg/125 mg orally every 24 hours, supplement after dialysis.
No specific GFR-based dose adjustment recommended; use caution in severe renal impairment (Cr Cl <30 m L/min) due to potential accumulation of fentanyl.
No specific adjustment recommended; use with caution in severe hepatic impairment (Child-Pugh C).
For Child-Pugh Class A or B: no adjustment required; for Child-Pugh Class C: reduce dose and monitor closely for toxicity due to reduced clearance.
3 months to 40 kg: 25-45 mg/kg/day of amoxicillin component in 2-3 divided doses; >40 kg: adult dosing.
Not approved for pediatric patients <18 years; safety and efficacy not established.
Adjust based on renal function; initiate with lower end of dosing due to age-related renal decline.
Initiate at the lowest available dose (100 mcg) and titrate cautiously; elderly patients may have altered pharmacokinetics and increased sensitivity to fentanyl.
None
Risk of respiratory depression, addiction, abuse, and misuse; risk of accidental ingestion; risk of medication errors resulting in fatal overdose; life-threatening respiratory depression in opioid-non-tolerant patients; risk of opioid analgesic drug interactions with CNS depressants; risk of neonatal opioid withdrawal syndrome with prolonged use during pregnancy.
Serious hypersensitivity reactions (anaphylaxis) can occur,Clostridium difficile-associated diarrhea (CDAD) risk,Hepatic dysfunction, including hepatitis and cholestatic jaundice, especially in elderly and patients with prior therapy,Renal impairment requires dose adjustment,Potential for superinfection with prolonged therapy
Respiratory depression, QT prolongation, serotonin syndrome, adrenal insufficiency, severe hypotension, seizures, biliary tract disease, gastrointestinal obstruction, withdrawal syndrome, and risk of overdose with alcohol or other CNS depressants.
History of hypersensitivity reaction to any penicillin,History of cholestatic jaundice or hepatic dysfunction associated with amoxicillin-clavulanate,Infectious mononucleosis (risk of erythematous rash)
Hypersensitivity to fentanyl or any components; opioid-non-tolerant patients; acute or severe bronchial asthma; known or suspected gastrointestinal obstruction; concurrent use of MAOIs or within 14 days of discontinuation.
May be taken with food to reduce GI irritation. No significant food interactions. Avoid high-fat meals if taking extended-release formulation (fat increases absorption variability).
Avoid grapefruit and grapefruit juice during treatment as they inhibit CYP3A4, increasing fentanyl exposure. No other significant food interactions; however, avoid alcohol due to additive CNS depressant effects. Maintain consistent meal timing relative to dosing to minimize variability.
FDA Category B. No evidence of teratogenicity in animal studies; human data do not indicate increased risk of major birth defects. However, use only when clearly needed in pregnancy, especially during first trimester. Theoretical risk of neonatal kernicterus if used near term due to bilirubin displacement from albumin.
FDA Pregnancy Category C. First trimester: Inadequate human data; opioid analgesics are not associated with major malformations but may cause neural tube defects at high doses in animal studies. Second trimester: No specific malformation risk. Third trimester: Prolonged use can cause neonatal opioid withdrawal syndrome (NOWS) and respiratory depression at birth.
Compatible with breastfeeding. Excreted into breast milk in low amounts (M/P ratio not established; amoxicillin milk concentration ~ 0.5-1% of maternal serum). No adverse effects reported in nursing infants. Consider monitoring for diarrhea or rash.
Minimal excretion into breast milk; M/P ratio not reported. Fentanyl is poorly absorbed orally, making significant infant exposure unlikely. Monitor infant for sedation, respiratory depression, and poor feeding. Avoid use in breastfeeding mothers with opioid dependence or high doses.
No routine dose adjustment in pregnancy despite increased renal clearance and expanded plasma volume. Standard adult dosing is appropriate unless GFR <30 m L/min. Monitor for therapeutic efficacy in pregnancy-related infections (e.g., UTIs, chorioamnionitis).
Pregnancy increases clearance and volume of distribution, potentially reducing drug levels. Dose adjustments may be needed: initiate with lower doses and titrate to effect; consider increasing frequency or using breakthrough doses. Monitor for inadequate analgesia. Avoid abrupt discontinuation; taper if stopping.
Administer with food to reduce GI upset. Monitor for rash, especially in patients with mononucleosis (EBV). Dose adjustment required for Cr Cl <30 m L/min. High dose (2000 mg amoxicillin) provides adequate coverage for penicillin-resistant S. pneumoniae. Avoid in penicillin allergy; cross-reactivity with cephalosporins is low but possible.
ABSTRAL (fentanyl sublingual spray) is a transmucosal immediate-release fentanyl (TIRF) formulation indicated for breakthrough pain in opioid-tolerant patients. Due to high bioavailability (~70%) and rapid onset (peak plasma concentration at 15-30 minutes), initial titration must start with 100 mcg, with dose escalation based on efficacy and tolerability. Weight-based conversion from other fentanyl products is not valid; utilize the provided conversion table. Patients must have a rescue agent (e.g., naloxone) available. Concomitant use with CYP3A4 inhibitors (e.g., ketoconazole, ritonavir) or inducers (e.g., rifampin, carbamazepine) requires dose adjustment. Avoid use in opioid-naïve patients due to risk of respiratory depression.
Take with food or milk to minimize stomach upset.,Complete the full course even if you feel better.,Shake oral suspension well before each use.,Use backup contraception if on oral contraceptives.,Contact doctor if rash, watery diarrhea, or signs of liver problems (yellowing skin, dark urine).,Do not take if allergic to penicillin or cephalosporins.
Use only for breakthrough cancer pain while on around-the-clock opioid therapy.,Do not switch from other fentanyl products based on dose; follow specific conversion instructions.,Spray entire dose into mouth; do not swallow or rinse for at least 10 minutes.,Store at room temperature, away from children and pets.,Dispose of unused units via drug take-back program or by flushing down toilet per FDA guidelines.,Never share this medication with others; death may occur.,Seek emergency if severe drowsiness, confusion, or slow breathing occurs.
"Amoxicillin may reduce the metabolism of Indinavir via inhibition of CYP3A4, leading to increased plasma concentrations of Indinavir. This can elevate the risk of Indinavir-related toxicities such as nephrolithiasis, hepatotoxicity, and gastrointestinal intolerance. Patients may experience exacerbated adverse effects without a corresponding increase in antiviral efficacy."
"Amoxicillin may inhibit the CYP3A4-mediated metabolism of nicardipine, a calcium channel blocker, leading to increased plasma concentrations of nicardipine. This can potentiate vasodilation and negative chronotropic effects, resulting in an increased risk of hypotension, bradycardia, and peripheral edema. Patients, especially those with pre-existing cardiovascular conditions, should be monitored for enhanced antihypertensive effects and adverse reactions when these drugs are coadministered."
"Amoxicillin may inhibit the metabolism of bortezomib through competitive inhibition of cytochrome P450 enzymes, particularly CYP3A4 and CYP2C19, potentially leading to increased bortezomib exposure. This interaction could result in enhanced toxicity of bortezomib, including peripheral neuropathy, myelosuppression, and gastrointestinal adverse effects. Clinicians should monitor for signs of bortezomib toxicity when amoxicillin is coadministered, especially in patients with pre-existing hepatic impairment or other risk factors."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about Amoxicillin-Clavulanate vs ABSTRAL, answered by our medical review team.
Amoxicillin-Clavulanate is a Penicillin Antibiotic + Beta-Lactamase Inhibitor that works by Amoxicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), inhibiting transpeptidation and autolysin inhibitors. Clavulanate is a beta-lactamase inhibitor that binds to and inactivates beta-lactamases, protecting amoxicillin from hydrolysis.. ABSTRAL is a Opioid Analgesic that works by Fentanyl is a potent mu-opioid receptor agonist, producing analgesia and sedation by activating G-protein coupled opioid receptors in the central nervous system.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between Amoxicillin-Clavulanate and ABSTRAL 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 Amoxicillin-Clavulanate is: 500 mg/125 mg orally every 8 hours or 875 mg/125 mg orally every 12 hours; intravenous: 1 g/0.2 g every 8 hours.. The standard adult dose of ABSTRAL is: For breakthrough pain in opioid-tolerant patients: initial dose 100 mcg sublingual tablet, titrate across strengths (100, 200, 300, 400, 600, 800 mcg) as needed; maximum 2 doses per episode, minimum 2 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 Amoxicillin-Clavulanate and ABSTRAL 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. Amoxicillin-Clavulanate is classified as Category C. FDA Category B. No evidence of teratogenicity in animal studies; human data do not indicate increased risk of major birth defects. However, use only when clearly needed in pregnanc. ABSTRAL is classified as Category C. FDA Pregnancy Category C. First trimester: Inadequate human data; opioid analgesics are not associated with major malformations but may cause neural tube defects at high doses in a. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.