Ampicillin and Sulbactam
**Ampicillin/sulbactam** is a parenteral potentiated aminopenicillin. It combines the broad-spectrum bactericidal activity of ampicillin with sulbactam, a beta-lactamase inhibitor. * **Spectrum of Activity**: Effective against many beta-lactamase-producing strains of *E. coli*, *Pasteurella* spp., *Staphylococcus* spp., *Klebsiella*, and *Proteus*. Also covers anaerobes like *Clostridium*, *Bacteroides*, *Fusobacterium*, and *Peptostreptococcus*. * **Clinical Utility**: Primarily used in dogs and cats when oral amoxicillin/clavulanate is not viable (e.g., patient is NPO, critically ill, or vomiting) or when high parenteral concentrations are required for severe infections like sepsis, pneumonia, or serious bite wounds. * **Limitations**: Ineffective against *Pseudomonas aeruginosa* and certain Type I beta-lactamase producers (*Citrobacter*, *Enterobacter*, *Serratia*). > **Clinical Pearl**: On a mg-for-mg basis, clavulanic acid is a more potent beta-lactamase inhibitor than sulbactam, but sulbactam offers advantages such as reduced likelihood of inducing chromosomal beta-lactamases, greater tissue penetration, and greater stability.
Mecanismo: * **Ampicillin** binds to **penicillin-binding proteins (PBPs)** located inside the bacterial cell wall → inhibits the third and final stage of bacterial cell wall synthesis → cell lysis and death. * **Sulbactam** irreversibly binds to and inactivates **beta-lactamases** (Richmond-Sykes types II-VI) → protects the **beta-lactam ring** of ampicillin from enzymatic hydrolysis. * *Note*: Sulbactam has weak intrinsic antibacterial activity against certain organisms (*Neisseria*, *Moraxella*, *Bacteroides*) by binding to specific PBPs, providing a synergistic effect when combined with ampicillin.
Dosificación por especie
- For respiratory infections using ampicillin/sulbactam (Unasyn®) · 50 mg/kg (combined) IV q8h · IV · q8h
- As adjunctive treatment of serious bite wounds · 30-50 mg/kg q8h IV · IV · q8h
- For intra-abdominal infections · 20 mg/kg IV or IM q6-8h · IV/IM · q6-8h · Extrapolation of human dose with limited studies in dogs and cats
- For respiratory infections · 50 mg/kg (combined) IV q8h · IV · q8h
- For respiratory infections · 20 mg/kg IV or IM q6-8h · IV/IM · q6-8h
- As adjunctive treatment of serious bite wounds · 30-50 mg/kg q8h IV · IV · q8h
- For intra-abdominal infections · 20 mg/kg IV or IM q6-8h · IV/IM · q6-8h · Extrapolation of human dose with limited studies in dogs and cats
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- Patients with a history of severe hypersensitivity (e.g., anaphylaxis) to penicillins
Efectos adversos
- Pain at intramuscular injection sites
- Thrombophlebitis (with intravenous injection)
- Hypersensitivity reactions (including severe anaphylaxis, particularly after IV administration)
- Neurotoxicity (e.g., ataxia in dogs) at high doses or prolonged use
- Elevated liver enzymes
- Tachypnea, dyspnea, edema, and tachycardia (reported in dogs)
Interacciones farmacológicas
- Aminoglycosides (amikacin, gentamicin, tobramycin) · In vitro inactivation if mixed together; synergistic in vivo, but penicillins can inactivate aminoglycosides in patients with renal failure or when used in massive dosages. Amikacin is the most resistant to this inactivation.
- Bacteriostatic antimicrobials (chloramphenicol, macrolides, tetracyclines, sulfonamides) · Potential in vitro antagonism between beta-lactam antibiotics and bacteriostatic antibiotics; clinical importance is unclear.
- Probenecid · Reduces the renal tubular secretion of both ampicillin and sulbactam, maintaining higher systemic levels for a longer period.
Monitorización
- Clinical efficacy (resolution of infection signs)
- Adverse effects (signs of hypersensitivity, neurological symptoms at high doses)
Sobredosis
Neurological effects (e.g., ataxia) have rarely been reported in dogs receiving very high dosages of penicillins. In humans, very high dosages of parenteral penicillins, especially in those with renal disease, have induced CNS effects. If neurological signs develop, weigh the risks of continued use versus dosage reduction or switching to a different antibiotic class.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.