Tazobactam: Beta Lactamase Inhibitor in fixed combination with Piperacillin or Ceftolozan

Tazobactam is a penicillanic acid sulfone and belongs to the classical beta lactamase inhibitors such as sulbactam and clavulanic acid. It has only weak antibacterial properties itself but protects its companion antibiotic from enzymatic degradation by bacterial beta lactamases. In clinical practice, tazobactam is encountered almost exclusively in two fixed combinations: piperacillin/tazobactam (Tazobac, Piperacillin Tazobactam generics) and ceftolozan/tazobactam (Zerbaxa).

Piperacillin/tazobactam is among the most frequently prescribed reserve antibiotics in hospital care. It is typically used in nosocomial infections, febrile neutropenia, complicated intraabdominal infections, and severe pneumonia. Ceftolozan/tazobactam is a newer combination for multidrug-resistant gram-negative pathogens, especially Pseudomonas aeruginosa. In both cases, antibiotic stewardship strategy determines targeted use, because broad use promotes resistance development.

Mechanism of Action

Beta lactam antibiotics work by inhibiting bacterial cell wall synthesis by covalently binding to penicillin binding proteins (PBP). However, many bacteria produce beta lactamases, enzymes that split the beta lactam ring and render the antibiotic ineffective. Tazobactam itself possesses a beta lactam ring and acts as a suicide substrate: it binds irreversibly to class A beta lactamases (TEM, SHV, CTX M) as well as some class C and D enzymes and permanently inactivates them.

The protective effect extends primarily to penicillinases of Staphylococcus aureus, beta lactamases of many Enterobacteriaceae (E. coli, Klebsiella, Proteus) and some anaerobes (Bacteroides fragilis). Against highly relevant carbapenemases (KPC, NDM, OXA 48), tazobactam is practically ineffective, which is why carbapenems or newer beta lactam beta lactamase inhibitor combinations such as ceftazidime/avibactam are used when such pathogens are suspected.

Indications

• Nosocomial pneumonia: including ventilator-associated pneumonia, often initially empirical
• Complicated intraabdominal infections: peritonitis, cholangitis, perforated diverticulitis
• Complicated urinary tract infections and pyelonephritis: when Pseudomonas or ESBL producers are suspected
• Skin and soft tissue infections: diabetic foot syndrome, necrotizing fasciitis (in combination)
• Febrile neutropenia: empirical first-line therapy per IDSA guideline
• Sepsis of unknown source in adults: calculated initial therapy in hospitals with relevant ESBL prevalence

Dosage and Administration

Piperacillin/tazobactam (4 g/0.5 g): Standard 4.5 g intravenously every 8 hours with normal renal function. In severe pneumonia, Pseudomonas suspicion, or critically ill patients, 4.5 g every 6 hours or prolonged infusion over 4 hours is often preferred to maximize time-dependent effect.

Renal impairment: Dose adjustment necessary. At eGFR 20 to 40 ml/min 4.5 g every 8 hours, at eGFR under 20 ml/min 4.5 g every 12 hours. With hemodialysis, additional dose after dialysis. Ceftolozan/tazobactam (1 g/0.5 g): 1.5 g intravenously every 8 hours for intraabdominal and urinary tract infections, 3 g every 8 hours for nosocomial pneumonia.

Adverse Effects

Common: Diarrhea, nausea, vomiting, rash, elevated liver transaminases, eosinophilia, local phlebitis at the infusion site.

Occasional to rare: Clostridioides difficile associated diarrhea and pseudomembranous colitis, acute renal failure especially in combination with vancomycin (AKI risk significantly elevated in studies), thrombocytopenia, neutropenia with prolonged use, fever reaction, severe skin reactions such as Stevens Johnson syndrome, acute interstitial nephritis.

Important: Patients with known penicillin allergy should avoid tazobactam combinations, as cross reactions are possible. In case of prior mild reaction, individual risk-benefit assessment determines the decision.

Drug Interactions

• Intravenous vancomycin: significantly increased risk of acute kidney injury; close creatinine monitoring or consider alternative such as linezolid
• Aminoglycosides (gentamicin, tobramycin): physically incompatible in the same infusion line, separate administration
• Methotrexate: reduced renal clearance of MTX, toxicity increases
• Vecuronium and other muscle relaxants: prolonged neuromuscular blockade
• Probenecid: prolonged half-life of both components
• Oral anticoagulants: possible INR elevation with prolonged therapy

Special Information

Pregnancy: Beta lactams including piperacillin and tazobactam are considered relatively safe in pregnancy, use follows strict indication. Breastfeeding: both substances pass into breast milk in small amounts, clinically relevant effects in the infant are not reported.

Antibiotic stewardship: Tazobactam combinations are reserve antibiotics. De-escalation to a targeted antibiotic occurs as soon as microbiological results are available. Routine use in uncomplicated infections is explicitly not recommended in S3 guidelines.

Monitoring: Creatinine and liver values every 2 to 3 days, blood count for therapy over seven days, observe stool frequency (CDI risk). In critically ill patients, therapeutic drug monitoring (TDM) for piperacillin may be useful.

You may also be interested in

• Piperacillin, the companion partner of tazobactam
• Imipenem, carbapenem when carbapenemase is suspected
• Amoxicillin, classical aminopenicillin
• Flucloxacillin, penicillinase resistant penicillin
• Ceftriaxon, third generation cephalosporin

Frequently Asked Questions

Sources

• EMA, Zerbaxa (Ceftolozan/Tazobactam) EPAR
• AWMF S3 Guideline Sepsis and nosocomial pneumonia
• Gelbe Liste, Piperacillin Tazobactam
• BfArM, Federal Institute for Drugs and Medical Devices