What the label lists and what reports show
Ceftolozane and tazobactam side effects
Ceftolozane and tazobactam's FDA label: “The most common adverse reactions in adult patients (≥5% in either the cIAI or cUTI indication) are nausea, diarrhea, headache, and pyrexia.” FAERS holds 965 reports naming it through July 30, 2026; the reaction reported most often, leaving out the conditions it is used for, product-use terms and outcomes, is pathogen resistance (54 reports).
- No generic listed
Check it at the source: the ceftolozane and tazobactam FDA label on DailyMed (effective May 12, 2026, Merck Sharp & Dohme LLC); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe most common adverse reactions in adult patients (≥5% in either the cIAI or cUTI indication) are nausea, diarrhea, headache, and pyrexia.
Table 7: Adverse Reactions Occurring in 1% or Greater of Adult Patients Receiving ZERBAXA in Phase 3 cIAI and cUTI Clinical Trials (Trial 1 and Trial 2)
| Reaction | ZERBAXA The ZERBAXA for injection dose was 1.5 g intravenously every 8 hours, adjusted to… | Meropenem (N=497) n (%) | ZERBAXA (N=533) n (%) | Levofloxacin (N=535) n (%) |
|---|---|---|---|---|
| Nausea | 38 (7.9) | 29 (5.8) | 15 (2.8) | 9 (1.7) |
| Headache | 12 (2.5) | 9 (1.8) | 31 (5.8) | 26 (4.9) |
| Diarrhea | 30 (6.2) | 25 (5) | 10 (1.9) | 23 (4.3) |
| Pyrexia | 27 (5.6) | 20 (4) | 9 (1.7) | 5 (0.9) |
| Constipation | 9 (1.9) | 6 (1.2) | 21 (3.9) | 17 (3.2) |
| Insomnia | 17 (3.5) | 11 (2.2) | 7 (1.3) | 14 (2.6) |
| Vomiting | 16 (3.3) | 20 (4) | 6 (1.1) | 6 (1.1) |
| Hypokalemia | 16 (3.3) | 10 (2) | 4 (0.8) | 2 (0.4) |
| ALT increased | 7 (1.5) | 5 (1) | 9 (1.7) | 5 (0.9) |
| AST increased | 5 (1) | 3 (0.6) | 9 (1.7) | 5 (0.9) |
| Anemia | 7 (1.5) | 5 (1) | 2 (0.4) | 5 (0.9) |
| Thrombocytosis | 9 (1.9) | 5 (1) | 2 (0.4) | 2 (0.4) |
| Abdominal pain | 6 (1.2) | 2 (0.4) | 4 (0.8) | 2 (0.4) |
| Anxiety | 9 (1.9) | 7 (1.4) | 1 (0.2) | 4 (0.7) |
| Dizziness | 4 (0.8) | 5 (1) | 6 (1.1) | 1 (0.2) |
| Hypotension | 8 (1.7) | 4 (0.8) | 2 (0.4) | 1 (0.2) |
| Atrial fibrillation | 6 (1.2) | 3 (0.6) | 1 (0.2) | 0 |
| Rash | 8 (1.7) | 7 (1.4) | 5 (0.9) | 2 (0.4) |
Rows and numbers as the label prints them, under its own column headings (the first rows of a longer table where it runs on). A reaction in a trial table is not necessarily caused by the medicine, and trials differ from everyday use.
From the label: adverse reactions, continuedThe following serious reactions are described in greater detail in the Warnings and Precautions section: Hypersensitivity reactions [see Warnings and Precautions (5.2) ] Clostridioides difficile -associated diarrhea [see Warnings and Precautions (5.3) ] Adult cIAI, cUTI and HABP/VABP Patients: The most common adverse reactions in adult patients (≥5% in either the cIAI or cUTI indication) are nausea, diarrhea, headache, and pyrexia. ( 6.1 ) The most common adverse reactions (≥5% in the HABP/VABP indication) are increase in hepatic transaminases, renal impairment/renal failure, and diarrhea. ( 6.1 ) Pediatric cIAI, cUTI and HABP/VABP Patients: The most common adverse reactions in pediatric patients (≥7% in cIAI, cUTI, or HABP/VABP) are thrombocytosis, diarrhea, pyrexia, leukopenia, abdominal pain, vomiting, increased aspartate aminotransferase, increased alanine aminotransferase, and anemia. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Merck Sharp & Dohme LLC at 1-877-888-4231 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and also may not reflect rates observed in practice.
Source: FDA drug label, NDA206829 (Cubist Pharms Llc), as published by Merck Sharp & Dohme LLC, effective May 12, 2026 (SPL set 70ac1d90-eff3-4f0b-9f46-5846c571b32f), via openFDA; the full label on DailyMed
What do FAERS reports show?
965 reports list ceftolozane and tazobactam among the medicines taken, each a report of something that happened, not proof the medicine caused it; 228 are coded as a death and 265 as a hospital stay. Counts follow how widely a medicine is used and watched, and they are not a measure of how risky it is. Of the 15 reactions below, 2 are named by the same term (in US spelling) in the label's adverse reactions, warnings or patient leaflet; a reaction the label does not name may still be there under another word, and a report does not show that the medicine caused it.
Reports received each year
The 25 most reported reactions
Source: FDA Adverse Event Reporting System (FAERS) via openFDA, reports through July 30, 2026; reactions as MedDRA preferred terms
What next?
- Ceftolozane and tazobactam: the full record
- label, generics, price, shortages, recalls
- Report a side effect to the FDA
- MedWatch
- Side effects hub
- the most reported medicines and reactions