What the label lists and what reports show
Ampicillin and sulbactam side effects
Ampicillin and sulbactam's FDA label: “The most frequently reported adverse reactions were diarrhea in 3% of the patients and rash in less than 2% of the patients.” FAERS holds 2,564 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 pyrexia (202 reports).
- Generic listed
Check it at the source: the ampicillin and sulbactam FDA label on DailyMed (effective July 10, 2026, Roerig); the FDA FAERS public dashboard.
What does the label list?
From the label: adverse reactionsThe most frequently reported adverse reactions were diarrhea in 3% of the patients and rash in less than 2% of the patients.
From the label: adverse reactions, continuedAdult Patients UNASYN is generally well tolerated. The following adverse reactions have been reported in clinical trials. Local Adverse Reactions Pain at IM injection site – 16% Pain at IV injection site – 3% Thrombophlebitis – 3% Phlebitis – 1.2% Systemic Adverse Reactions The most frequently reported adverse reactions were diarrhea in 3% of the patients and rash in less than 2% of the patients. Additional systemic reactions reported in less than 1% of the patients were: itching, nausea, vomiting, candidiasis, fatigue, malaise, headache, chest pain, flatulence, abdominal distension, glossitis, urine retention, dysuria, edema, facial swelling, erythema, chills, tightness in throat, substernal pain, epistaxis and mucosal bleeding. Pediatric Patients Available safety data for pediatric patients treated with UNASYN demonstrate a similar adverse events profile to those observed in adult patients. Additionally, atypical lymphocytosis has been observed in one pediatric patient receiving UNASYN. Adverse Laboratory Changes Adverse laboratory changes without regard to drug relationship that were reported during clinical trials were: Hepatic: Increased AST (SGOT), ALT (SGPT), alkaline phosphatase, and LDH. Hematologic: Decreased hemoglobin, hematocrit, RBC, WBC, neutrophils, lymphocytes, platelets and increased lymphocytes, monocytes, basophils, eosinophils, and platelets. …
Source: FDA drug label, NDA050608 (Pfizer), as published by Roerig, effective July 10, 2026 (SPL set 155c7ec0-5862-404f-b1d0-f278f8a8bbda), via openFDA; the full label on DailyMed
What do FAERS reports show?
2,564 reports list ampicillin and sulbactam among the medicines taken, each a report of something that happened, not proof the medicine caused it; 522 are coded as a death and 1,375 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 21 reactions below, 8 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?
- Ampicillin and sulbactam: 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