Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
A/T/S vs COMBOGESIC
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
A/T/S (erythromycin) is a macrolide antibiotic that acts by binding to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis and bacterial growth.
COMBOGESIC (acetaminophen and tramadol) combines a centrally acting analgesic (tramadol) that binds to mu-opioid receptors and inhibits serotonin and norepinephrine reuptake, with an antipyretic (acetaminophen) that inhibits cyclooxygenase (COX) in the CNS.
Treatment of acne vulgaris (FDA-approved indication),Treatment of bacterial infections caused by susceptible organisms (off-label use for acne is the primary use)
Management of acute pain severe enough to require an opioid analgesic and for which alternative treatments are inadequate in adults
Dosing is individualized based on antithrombin activity level. For acute thrombotic events: initial bolus of 30-50 IU/kg followed by maintenance dosing to achieve target activity levels (80-120% of normal). Prophylaxis: 40-60 IU/kg every 24 hours.
One tablet (acetaminophen 500 mg / tramadol 37.5 mg) orally every 4 to 6 hours as needed for pain, not to exceed 8 tablets per day.
Terminal elimination half-life: 1–2 hours (prolonged in hepatic impairment).
Acetaminophen: 2-3 hours; Tramadol: 6.3 hours (slow CYP2D6 metabolizers may exceed 12 hours). Clinically, dosing interval adjusted for renal impairment.
Antithrombin is a glycoprotein; its metabolism involves cellular uptake and catabolism, but specific CYP450 enzymes are not involved. Degradation occurs via proteolysis and reticuloendothelial system clearance.
Tramadol: primarily metabolized by CYP2D6 and CYP3A4; O-desmethyltramadol (active metabolite) via CYP2D6. Acetaminophen: primarily metabolized by glucuronidation and sulfation in the liver.
Renal: 10-20% (active drug and metabolites); Fecal: minimal; Biliary: not significant.
Renal excretion of acetaminophen metabolites (glucuronide, sulfate, cysteine, and mercapturate conjugates); 85% total. Tramadol and metabolites: 90% renal, 10% fecal.
70-90% bound to serum albumin.
Acetaminophen 10-25%; Tramadol 20% bound to albumin.
0.5–0.8 L/kg (low Vd, minimal tissue penetration).
Acetaminophen 0.9 L/kg; Tramadol 2.6 L/kg. Reflects extensive tissue distribution.
Topical: 1–5% (minimal systemic absorption).
Acetaminophen oral ~88%; Tramadol oral ~75% (due to first-pass metabolism).
No specific adjustment required; drug is not renally eliminated.
For Cr Cl 30-59 m L/min: increase dosing interval to every 12 hours, maximum 4 tablets per day. For Cr Cl <30 m L/min: not recommended. Hemodialysis: administer dose after dialysis session, use with caution.
No specific adjustment; antithrombin is produced in the liver, but exogenous replacement does not require dose adjustment in hepatic impairment.
Child-Pugh Class A: no adjustment. Child-Pugh Class B: reduce dose by 50% or extend interval; maximum 4 tablets per day. Child-Pugh Class C: contraindicated.
Dosing based on weight and antithrombin levels; typical initial dose 30-50 IU/kg, followed by maintenance to achieve target levels. Clinical trial data limited in neonates.
Not recommended for pediatric use. Safety and efficacy not established in children.
No specific adjustment; use standard dosing with monitoring of antithrombin activity and bleeding risk.
Initiate at lowest effective dose; consider extended dosing interval (every 8-12 hours) and monitor for adverse effects, particularly CNS and respiratory depression.
None.
Risk of addiction, abuse, and misuse; life-threatening respiratory depression; accidental ingestion; neonatal opioid withdrawal syndrome; risk of medication errors (combining different forms of acetaminophen leading to hepatotoxicity); serious, life-threatening, or fatal respiratory depression may occur when used with benzodiazepines or other CNS depressants.
Hypersensitivity reactions including anaphylaxis have occurred.,Prolonged use may result in overgrowth of nonsusceptible organisms including fungi.,Use with caution in patients with hepatic impairment.,Potential for QT prolongation and ventricular arrhythmias, especially with intravenous administration or concomitant drugs that prolong QT interval.
Addiction, abuse, and misuse; life-threatening respiratory depression; neonatal opioid withdrawal syndrome; risks from concomitant use with benzodiazepines or other CNS depressants; hepatotoxicity (associated with acetaminophen); seizures; serotonin syndrome; risk of overdose; interactions with MAOIs; CYP2D6 poor metabolizers may have reduced efficacy; risk of anaphylaxis and hypersensitivity.
Hypersensitivity to erythromycin or any macrolide antibiotic.,Use with caution in patients with pre-existing QT prolongation or electrolyte abnormalities (relative contraindication).
Hypersensitivity to tramadol, acetaminophen, or any component; significant respiratory depression; acute or severe bronchial asthma in an unmonitored setting or without resuscitative equipment; known or suspected gastrointestinal obstruction, including paralytic ileus; concomitant use of MAOIs or within 14 days of such therapy.
No specific food interactions. Avoid excessive alcohol consumption as it may increase skin dryness.
Avoid alcohol while taking Combogesic, as it increases the risk of liver damage with acetaminophen and gastrointestinal bleeding with ibuprofen. Taking with food may reduce gastric irritation. No specific food restrictions.
FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; no adequate human studies in first trimester. Topical erythromycin has minimal systemic absorption; risk to fetus is low across all trimesters.
Combogesic contains paracetamol (acetaminophen) and tramadol. Paracetamol: No increased risk of major malformations; first trimester use is generally considered low risk. Second and third trimester: No known fetal toxicity at therapeutic doses. Tramadol: First trimester: Limited data, but no major teratogenicity observed in animal studies; human data insufficient to exclude risk. Second and third trimester: Not associated with structural anomalies; chronic use may lead to fetal dependence and neonatal withdrawal syndrome. At term: Risk of neonatal respiratory depression if used near delivery; tramadol may prolong labor and increase risk of postpartum hemorrhage.
Compatible with breastfeeding. Erythromycin is excreted into breast milk in small amounts (M/P ratio approximately 0.5). Topical use results in negligible systemic exposure; unlikely to cause adverse effects in nursing infants.
Paracetamol: Excreted into breast milk in small amounts (M/P ratio ~0.23-0.91); considered compatible with breastfeeding. Tramadol: Excreted into breast milk (M/P ratio ~1.5-2.0); relative infant dose ~2.24% of maternal weight-adjusted dose. Monitor infant for sedation and respiratory depression; avoid in women with CYP2D6 ultra-rapid metabolizer status due to increased risk of high morphine levels in breast milk.
No dose adjustment required. Systemic absorption from topical application is minimal and not significantly altered by pregnancy-related pharmacokinetic changes.
Paracetamol: No adjustment required; use lowest effective dose for shortest duration. Tramadol: Pregnancy may alter tramadol pharmacokinetics (increased clearance, decreased Cmax); however, no standard dose adjustment is recommended. Use minimal effective dose; avoid sustained-release formulations. Near term: Consider alternative analgesics to minimize neonatal effects.
A/T/S (erythromycin 2% topical solution) is indicated for acne vulgaris. Avoid contact with eyes, mouth, and mucous membranes. May cause skin dryness or irritation; use moisturizer. Effectiveness may decrease with prolonged use due to bacterial resistance. Not recommended for use with other topical erythromycin products or clindamycin to avoid antagonism.
Combogesic (paracetamol/acetaminophen + ibuprofen) is a fixed-dose combination used for acute pain. Note that the maximum daily dose of acetaminophen is 4000 mg (or lower in hepatic impairment) and ibuprofen 1200 mg (or lower in renal impairment). Avoid concomitant use of other NSAIDs or acetaminophen-containing products. Use with caution in patients with a history of peptic ulcer or bleeding disorders; ibuprofen may increase bleeding risk.
Apply a thin layer to affected areas twice daily after washing.,Avoid contact with eyes, lips, and mouth; if contact occurs, rinse thoroughly with water.,May cause stinging, burning, or peeling; if irritation persists, consult your doctor.,Use sunscreen daily as this medication may increase sensitivity to sunlight.,Do not use more than prescribed; overuse may increase side effects without improving results.,Inform your doctor if you are pregnant, planning to become pregnant, or breastfeeding.,Keep away from open flames or heat sources; product is flammable.
Do not exceed the recommended dose as it may cause liver damage or kidney problems.,Avoid taking other products containing acetaminophen or NSAIDs (e.g., ibuprofen, naproxen) while using Combogesic.,Take with food or milk to reduce stomach upset.,Report any signs of stomach bleeding (e.g., black/tarry stools, vomiting blood), rash, or swelling.,Do not use for more than 10 days for pain unless directed by a doctor.
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 A/T/S vs COMBOGESIC, answered by our medical review team.
A/T/S is a Macrolide antibiotic that works by A/T/S (erythromycin) is a macrolide antibiotic that acts by binding to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis and bacterial growth.. COMBOGESIC is a Analgesic Combination (Opioid + Non-Opioid) that works by COMBOGESIC (acetaminophen and tramadol) combines a centrally acting analgesic (tramadol) that binds to mu-opioid receptors and inhibits serotonin and norepinephrine reuptake, with an antipyretic (acetaminophen) that inhibits cyclooxygenase (COX) in the CNS.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between A/T/S and COMBOGESIC 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 A/T/S is: Dosing is individualized based on antithrombin activity level. For acute thrombotic events: initial bolus of 30-50 IU/kg followed by maintenance dosing to achieve target activity levels (80-120% of normal). Prophylaxis: 40-60 IU/kg every 24 hours.. The standard adult dose of COMBOGESIC is: One tablet (acetaminophen 500 mg / tramadol 37.5 mg) orally every 4 to 6 hours as needed for pain, not to exceed 8 tablets per day.. 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 A/T/S and COMBOGESIC 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. A/T/S is classified as Category C. FDA Pregnancy Category B. No evidence of teratogenicity in animal studies; no adequate human studies in first trimester. Topical erythromycin has minimal systemic absorption; risk . COMBOGESIC is classified as Category C. Combogesic contains paracetamol (acetaminophen) and tramadol. Paracetamol: No increased risk of major malformations; first trimester use is generally considered low risk. Second an. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.