UNASYN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for UNASYN (UNASYN).
Ampicillin inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs); sulbactam is a beta-lactamase inhibitor that prevents degradation of ampicillin by beta-lactamases.
| Metabolism | Ampicillin is primarily excreted unchanged in urine; sulbactam is also excreted renally with minimal hepatic metabolism. |
| Excretion | Renal: ampicillin (~75-90% unchanged) and sulbactam (~75-85% unchanged); biliary/fecal: minimal (<5% for each component). |
| Half-life | Ampicillin: ~1 hour (normal renal function); sulbactam: ~1-1.4 hours (normal renal function); prolonged in renal impairment (ampicillin up to 20 hours, sulbactam up to 10-15 hours in anuria). |
| Protein binding | Ampicillin: ~20% bound to albumin; sulbactam: ~38% bound to albumin. |
| Volume of Distribution | Ampicillin: 0.3-0.4 L/kg; sulbactam: 0.2-0.4 L/kg; distributes well into extracellular fluid and tissues (e.g., pleural fluid, bile, middle ear). |
| Bioavailability | IM: ~100% (both components); oral: not applicable (only parenteral formulation). |
| Onset of Action | IV: immediate (within minutes); IM: rapid (peak levels in 30-60 minutes). |
| Duration of Action | IV/IM: approximately 6-8 hours (requires q6h dosing for serious infections). |
3 g (ampicillin 2 g + sulbactam 1 g) IV every 6 hours; total daily dose of sulbactam not to exceed 4 g.
| Dosage form | INJECTABLE |
| Renal impairment | CrCl 15-29 mL/min: 1.5 g (ampicillin 1 g + sulbactam 0.5 g) IV every 12 hours; CrCl 5-14 mL/min: 1.5 g IV every 24 hours; hemodialysis: administer after dialysis. |
| Liver impairment | No adjustment required for mild-to-moderate hepatic impairment; not studied in severe hepatic disease. |
| Pediatric use | Children ≥1 year: 300 mg/kg/day (ampicillin 200 mg/kg + sulbactam 100 mg/kg) IV divided every 6 hours; neonates and infants <1 year: not established. |
| Geriatric use | Dose based on renal function; monitor for neurotoxicity; max daily sulbactam dose 4 g. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for UNASYN (UNASYN).
| Breastfeeding | Ampicillin and sulbactam are excreted into breast milk in low concentrations. M/P ratio not well established but estimated low. Generally considered compatible with breastfeeding; monitor infant for diarrhea or rash. |
| Teratogenic Risk | UNASYN (ampicillin/sulbactam) is classified as Pregnancy Category B. No evidence of teratogenicity in animal studies. Adequate human studies are lacking; use only if clearly needed. Risk of neonatal kernicterus if administered near term due to bilirubin displacement. |
| Fetal Monitoring |
■ FDA Black Box Warning
No black box warning.
| Serious Effects |
["Hypersensitivity to penicillins or sulbactam","Infections caused by beta-lactamase-negative ampicillin-resistant organisms","History of cholestatic jaundice or hepatic dysfunction with sulbactam/ampicillin combinations"]
| Precautions | ["Serious hypersensitivity reactions (anaphylaxis) especially in penicillin-allergic patients","Clostridium difficile-associated diarrhea (CDAD)","Seizures with high doses or renal impairment","Hepatotoxicity (elevated liver enzymes, hepatitis)","Renal impairment: dose adjustment required","Superinfection with prolonged use","Blood dyscrasias (neutropenia, thrombocytopenia)"] |
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| Monitor maternal renal function, signs of hypersensitivity, and diarrhea. Fetal monitoring for bradycardia or distress not routinely required unless maternal adverse effects occur. |
| Fertility Effects | No known adverse effects on fertility in animal or human studies. |