# Tazobactam
**Tazobactam** is a β-lactamase inhibitor of the penicillanic acid sulfone class that has little antibacterial activity of its own but is combined with β-lactam antibiotics, principally piperacillin and [ceftolozane](https://www.edgepedia.org/ceftolozane), to protect them from enzymatic degradation by bacterial β-lactamases.[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630) It is a sulbactam analog in which one exocyclic methyl hydrogen is replaced by a 1,2,3-triazol-1-yl group, a substitution made to raise inhibitory activity.[2](https://pubchem.ncbi.nlm.nih.gov/compound/123630?from=summary) The drug was originally synthesized in the 1980s by Taiho Pharmaceuticals of Tokyo and launched by Lederle (later Wyeth).[3](https://ndl.ethernet.edu.et/bitstream/123456789/91184/1/Drug%20Discovery%20A%20History-Walter%20Sneader-John%20Wiley%20%26%20Sons%20Ltd-2005-1.pdf)
| Key fact | Detail |
|---|---|
| Drug class | β-lactamase inhibitor (penicillanic acid sulfone); ATC code J01CG02[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630) |
| Chemistry | Formula C10H12N4O5S; molecular weight 300.29 g/mol; pKa 2.1[2](https://pubchem.ncbi.nlm.nih.gov/compound/123630?from=summary) • [4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9888030/) |
| First approval | 1993 (combination product); piperacillin-tazobactam approved by the FDA in 1994[2](https://pubchem.ncbi.nlm.nih.gov/compound/123630?from=summary) |
| Main combinations | Piperacillin (Zosyn/Tazocin, 8:1 ratio) and ceftolozane (Zerbaxa)[5](https://www.ema.europa.eu/en/documents/referral/tazocin-article-30-referral-assessment-report_en.pdf) • [6](https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/206829s023lbl.pdf) |
| Enzyme spectrum | Effective mainly against class A enzymes (OHIO-1, SHV-1, TEM groups); weak against AmpC; inactive against metallo-β-lactamases and carbapenemases[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630) • [7](https://onlinelibrary.wiley.com/doi/10.1155/ijm/4479031) |
| Elimination | Renal, with about 80% of the dose excreted unchanged; about 30% bound to plasma proteins[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630) |
| Half-life | 0.7 to 1.2 hours after a single dose in healthy volunteers given piperacillin-tazobactam[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630) |
## Mechanism of action
β-lactam antibiotics kill bacteria by interfering with cell-wall synthesis, but many Gram-negative organisms defend themselves with β-lactamase enzymes that hydrolyze the β-lactam ring. Tazobactam is a mechanism-based (suicide) inhibitor: it mimics a β-lactam substrate, is attacked by the enzyme's active site, and then forms an imine acyl complex that irreversibly inactivates the enzyme.[4](https://pmc.ncbi.nlm.nih.gov/articles/PMC9888030/) By removing the enzyme, tazobactam broadens the spectrum of its partner antibiotic against organisms that would otherwise degrade it.[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630)
The inhibitor's spectrum is bounded by enzyme class. Tazobactam is predominantly effective against the OHIO-1, SHV-1, and TEM groups of β-lactamases, and it may inhibit others, but AmpC cephalosporinases are not significantly inhibited by clavulanic acid, sulbactam, or tazobactam, and the drug has no activity against metallo-β-lactamases (class B) or carbapenemases such as KPC and OXA-48.[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630) • [8](https://www.bmj.com/content/391/bmj-2024-082681.full) • [7](https://onlinelibrary.wiley.com/doi/10.1155/ijm/4479031) Among the three classical inhibitors, tazobactam and clavulanic acid are more potent against plasmid-mediated β-lactamases than sulbactam, while tazobactam and sulbactam are more potent against chromosomally mediated enzymes than clavulanic acid.[9](https://academic.oup.com/cid/article-pdf/22/1/107/809715/22-1-107.pdf)
## Combinations and approved uses
**Piperacillin-tazobactam.** The parenteral combination of the ureidopenicillin piperacillin with tazobactam in an 8:1 ratio is approved for moderate to severe polymicrobial infections, including intra-abdominal, skin and soft-tissue, and other infections caused by susceptible Gram-positive and Gram-negative aerobic and anaerobic organisms.[5](https://www.ema.europa.eu/en/documents/referral/tazocin-article-30-referral-assessment-report_en.pdf) In the United States, ZOSYN is indicated for intra-abdominal infections, nosocomial pneumonia, skin and skin structure infections, female pelvic infections, and community-acquired pneumonia, in adults and in pediatric patients 2 months of age and older.[10](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8db6bd91-2106-4bfd-8cc8-38aaf1e18d17) The combination was first marketed in France in 1992 under the name [Tazocin](https://www.edgepedia.org/piperacillin-tazobactam) and reached the United Kingdom, Germany, Switzerland, and the United States in 1993.[11](https://patents.google.com/patent/CN118994197A/zh)
**Ceftolozane-tazobactam.** The second-generation pairing pairs tazobactam with the antipseudomonal cephalosporin ceftolozane (Zerbaxa), initially approved in the United States in 2014; in June 2019 the FDA added hospital-acquired bacterial pneumonia and ventilator-associated bacterial pneumonia (HABP/VABP) to the indications.[2](https://pubchem.ncbi.nlm.nih.gov/compound/123630?from=summary) The current label covers complicated intra-abdominal infections (with metronidazole), complicated urinary tract infections including pyelonephritis, and HABP/VABP in adult and pediatric patients at least 32 weeks gestational age, dosed at 1.5 g (1 g ceftolozane plus 0.5 g tazobactam) every 8 hours for cIAI and cUTI and 3 g (2 g plus 1 g) every 8 hours for HABP/VABP.[6](https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/206829s023lbl.pdf) Ceftolozane-tazobactam has shown moderate activity against multidrug-resistant and difficult-to-treat-resistant *Pseudomonas aeruginosa*, particularly in the absence of carbapenemases.[12](https://link.springer.com/article/10.1007/s11908-025-00874-y)
## Pharmacokinetics
Tazobactam is given parenterally and is cleared by the kidneys as a substrate of the transporters OAT1 and OAT3, so inhibitors of these transporters should be avoided and doses of both piperacillin-tazobactam and ceftolozane-tazobactam must be adjusted in renal impairment.[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630) About 80% of an administered dose is eliminated unchanged in urine, roughly 30% is bound to plasma proteins, and the plasma half-life after a single dose of piperacillin-tazobactam in healthy volunteers is 0.7 to 1.2 hours.[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630) The remainder is excreted as M1, an inactive metabolite formed by hydrolysis of the β-lactam ring.[1](https://pubchem.ncbi.nlm.nih.gov/compound/123630)
## Clinical evidence
Piperacillin-tazobactam is among the most widely used empirical regimens for hospitalized adults with suspected infection. The ACORN randomized trial (2,511 adults at [Vanderbilt University Medical Center](https://www.edgepedia.org/vanderbilt-university-medical-center), 2021 to 2022) compared it with cefepime and found no significant difference in the highest stage of acute kidney injury or death, while neurological dysfunction was more common with cefepime.[13](https://pmc.ncbi.nlm.nih.gov/articles/PMC10576861/) In complicated urinary tract infection and acute pyelonephritis, the ALLIUM phase 3 trial found that cefepime combined with the tazobactam derivative [enmetazobactam](https://www.edgepedia.org/enmetazobactam) achieved a composite cure rate of 79.1% at day 14 versus 58.9% for piperacillin-tazobactam, meeting criteria for both noninferiority and superiority.[14](https://jamanetwork.com/journals/jama/fullarticle/2796946)
For multidrug-resistant *P. aeruginosa*, ceftolozane-tazobactam and ceftazidime-avibactam are both considered first-line options, and comparative evidence has given mixed results. A 2025 systematic review and meta-analysis of six observational studies (1,161 patients) found higher clinical cure with ceftolozane-tazobactam after confounder adjustment (odds ratio 1.82, 95% CI 1.10 to 2.99), with no difference in microbiological failure, 90-day resistance development, or 30-day mortality.[15](https://pubmed.ncbi.nlm.nih.gov/41844194/) A separate GRADE-assessed meta-analysis found no significant differences between the two regimens across clinical success, mortality, recurrence, resistance emergence, and microbiological response, with certainty of evidence ranging from low to very low.[16](https://pmc.ncbi.nlm.nih.gov/articles/PMC13236363/) A Merck-supported network meta-analysis against aminoglycosides and polymyxins favored ceftolozane-tazobactam for clinical cure and all-cause mortality.[17](https://journals.asm.org/doi/10.1128/aac.00735-25)
## Resistance and limitations
Resistance to tazobactam combinations arises through several routes: hyperproduction of chromosomal AmpC enzymes, which the inhibitor does not block; acquisition of carbapenemases or metallo-β-lactamases; loss of porins; and inhibitor-resistant variants of class A enzymes, such as SHV mutants in which single amino-acid substitutions raise the IC50 of tazobactam tenfold.[8](https://www.bmj.com/content/391/bmj-2024-082681.full) • [18](https://academic.oup.com/femsre/article/24/3/251/561791) • [1](https://pubchem.ncbi.nlm.nih.gov/compound/123630) For ceftolozane-tazobactam, resistance in *P. aeruginosa* can also develop through AmpC mutations and extended-spectrum OXA-type enzymes.[7](https://onlinelibrary.wiley.com/doi/10.1155/ijm/4479031)
Supply has also been a practical constraint: the UK ESPAUR report attributed fluctuations in ceftolozane-tazobactam consumption to a drug shortage in 2021.[19](https://assets.publishing.service.gov.uk/media/6936ac34b612700b2cb73607/ESPAUR-report-2024-to-2025.pdf)
## References
1. [Tazobactam, CID 123630, PubChem](https://pubchem.ncbi.nlm.nih.gov/compound/123630)
2. [Tazobactam, PubChem summary (ChEBI/DrugBank annotations)](https://pubchem.ncbi.nlm.nih.gov/compound/123630?from=summary)
3. [Walter Sneader (2005). Drug Discovery: A History, John Wiley & Sons](https://ndl.ethernet.edu.et/bitstream/123456789/91184/1/Drug%20Discovery%20A%20History-Walter%20Sneader-John%20Wiley%20%26%20Sons%20Ltd-2005-1.pdf)
4. [Biochemical exploration of β-lactamase inhibitors, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC9888030/)
5. [Tazocin Article 30 referral, CHMP assessment report, EMA (2011)](https://www.ema.europa.eu/en/documents/referral/tazocin-article-30-referral-assessment-report_en.pdf)
6. [ZERBAXA (ceftolozane and tazobactam) prescribing information, FDA](https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/206829s023lbl.pdf)
7. [Gourabi et al. A Review of β-Lactamase Inhibitors in Clinical Use and Development, International Journal of Microbiology](https://onlinelibrary.wiley.com/doi/10.1155/ijm/4479031)
8. [Antimicrobial use and resistance, The BMJ](https://www.bmj.com/content/391/bmj-2024-082681.full)
9. [Review articles on β-lactamase inhibitors, Clinical Infectious Diseases](https://academic.oup.com/cid/article-pdf/22/1/107/809715/22-1-107.pdf)
10. [ZOSYN (piperacillin and tazobactam) label, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=8db6bd91-2106-4bfd-8cc8-38aaf1e18d17)
11. [CN118994197A: preparation method for tazobactam sodium, Google Patents](https://patents.google.com/patent/CN118994197A/zh)
12. [Filling the Gaps: A Review and Update on Beta-Lactamase Inhibitor Combinations, Current Infectious Disease Reports](https://link.springer.com/article/10.1007/s11908-025-00874-y)
13. [Cefepime vs Piperacillin-Tazobactam in Adults Hospitalized With Acute Infection: The ACORN Randomized Clinical Trial, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC10576861/)
14. [Effect of Cefepime/Enmetazobactam vs Piperacillin/Tazobactam in Complicated UTI or Acute Pyelonephritis, JAMA](https://jamanetwork.com/journals/jama/fullarticle/2796946)
15. [Comparison of Ceftolozane-Tazobactam and Ceftazidime-Avibactam in MDR/DTR Pseudomonas aeruginosa Infections: Systematic Review and Meta-analysis, PubMed](https://pubmed.ncbi.nlm.nih.gov/41844194/)
16. [Comparative efficacy of ceftolozane–tazobactam versus ceftazidime–avibactam for Pseudomonas aeruginosa infections, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC13236363/)
17. [Systematic literature review and (network) meta-analysis of ceftolozane/tazobactam effectiveness, Antimicrobial Agents and Chemotherapy](https://journals.asm.org/doi/10.1128/aac.00735-25)
18. [Molecular basis of antibiotic resistance and β-lactamase inhibition by mechanism-based inactivators, FEMS Microbiology Reviews](https://academic.oup.com/femsre/article/24/3/251/561791)
19. [ESPAUR report 2024 to 2025, UK Health Security Agency](https://assets.publishing.service.gov.uk/media/6936ac34b612700b2cb73607/ESPAUR-report-2024-to-2025.pdf)
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*Topic: Encyclopedia › Physical world and mathematics › Chemistry › Organic substances › Pharmaceutical and drug molecules › Antibacterial antibiotics*
*Initially written Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license