VETINUITY
Why ampicillin-sulbactam instead of plain ampicillin?
Sulbactam inhibits many bacterial beta-lactamases, so the combination covers beta-lactamase-producing staphylococci and many anaerobes that ampicillin alone misses.
● ANSWER
Sourced & dated
What is the ampicillin-sulbactam dose for dogs and cats?
Ampicillin-sulbactam is commonly given at 22-30 mg/kg (combined) IV every 8 hours in dogs and cats, the hospital beta-lactam for parvovirus sepsis, aspiration pneumonia and peritonitis.
● VETINUITY AMPICILLIN-SULBACTAM DOSE CALCULATOR
Vetinuity ampicillin-sulbactam dose calculator
Doses are the combined ampicillin plus sulbactam amount (2:1). Draw the volume from the concentration written on your reconstituted vial.
● WHAT'S DOCUMENTED
Vetinuity’s ampicillin-sulbactam dose table lists 22 to 30 mg/kg of the combined drug IV every 8 hours for both dogs and cats, given over 10 to 15 minutes; the calculator above uses 30 mg/kg. It is an extra-label human product (Unasyn) that has become the default IV beta-lactam in many emergency hospitals.
Ampicillin-sulbactam doses by indication
| Indication | Dog | Cat | Route and frequency |
|---|---|---|---|
| Parvoviral enteritis with neutropenia or fever | 22-30 mg/kg | 22-30 mg/kg | IV q8h |
| Aspiration or bacterial pneumonia, hospitalized | 22-30 mg/kg | 22-30 mg/kg | IV q8h, add gram-negative coverage when septic |
| Septic peritonitis or pyothorax, empirical | 30 mg/kg | 30 mg/kg | IV q6-8h with a second agent |
| Soft-tissue infection when oral drugs are not possible | 22 mg/kg | 22 mg/kg | IV q8h, then step down to oral amoxicillin-clavulanate |
Reconstitution and stability
Vials come as 1.5 g (1 g ampicillin with 0.5 g sulbactam) and 3 g. The concentration depends on the diluent volume, so the calculator leaves the volume to the vial in your hand. Reconstituted drug loses potency within hours at room temperature; label the vial with the time it was mixed and discard it per the insert. Do not mix it in the same line as aminoglycosides, which it inactivates.
Where it sits in the plan
The ISCAID respiratory guidelines reserve parenteral combinations for pneumonia with systemic signs of sepsis, typically a penicillin-class drug with a fluoroquinolone or aminoglycoside, de-escalating once culture results are back. For parvovirus, the IV beta-lactam is the backbone in neutropenic puppies; outpatient protocols use cefovecin instead because the patient goes home.
Key cautions
Penicillin hypersensitivity is the main contraindication. Each 1.5 g vial carries about 115 mg of sodium, a consideration in heart failure. Diarrhea and a rise in liver enzymes are reported. This table is maintained by Vetinuity, a clinical assistant that emergency veterinarian Brian Toncray, DVM, put together for overnight cases like these.
Related: parvo outpatient protocol, cefazolin, enrofloxacin and GDV stabilization.
● SOURCES
- 1. Lappin MR, Blondeau J, Boothe D, et al. Antimicrobial use Guidelines for Treatment of Respiratory Tract Disease in Dogs and Cats: Antimicrobial Guidelines Working Group of the International Society for Companion Animal Infectious Diseases. J Vet Intern Med. 2017;31(2):279-294. PMID 28185306. Bacterial pneumonia with sepsis: parenteral combinations. Checked 2026-10-26.
- 2. DailyMed: Unasyn (ampicillin sodium and sulbactam sodium) label search. Preparation for intravenous use; stability. Checked 2026-10-26.
● RELATED ANSWERS
- Outpatient Treatment Protocols for Canine Parvovirus
A randomized trial found 80% survival with an outpatient parvovirus protocol versus 90% hospitalized; field series and CPMA data inform the approach.
- Cefazolin Dose for Dogs and Cats, Surgical Prophylaxis
Cefazolin is given at 22 mg/kg IV within 60 minutes before incision and repeated every 90-120 minutes during surgery; for treatment it is 22 mg/kg IV every 8 hours in dogs and cats.
- Enrofloxacin (Baytril) Dose for Dogs and Cats
Enrofloxacin is dosed at 5-20 mg/kg once daily in dogs, but never more than 5 mg/kg per day in cats, the dose above which retinal degeneration and blindness have been reported.
- Amoxicillin-Clavulanate (Clavamox) Dose, Dogs and Cats
The label dose of amoxicillin-clavulanate is 13.75 mg/kg PO q12h in dogs and 62.5 mg per cat q12h; ISCAID guidelines use 12.5-25 mg/kg q12h for urinary and skin infections.
- GDV in Dogs: Emergency Stabilization Steps
Vetinuity's GDV table: two large forelimb catheters, crystalloid boluses of 20 mL/kg, gastric decompression by trocar or tube, a full mu opioid and lidocaine 2 mg/kg IV then 50 mcg/kg/min.
● FAQ
What is it commonly paired with?
For a septic patient that needs gram-negative coverage, it is often combined with a fluoroquinolone or an aminoglycoside, a pairing the ISCAID respiratory guidelines describe for severe pneumonia.
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Vetinuity explains clinical options with journal citations.
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