A Phase 3 interventional study of Antibiotic - standard duration and Antibiotic - fixed-extended-duration in Complicated Intra-abdominal Infection, sponsored by Lydia Flett. Active, not recruiting at 36 sites in United Kingdom. Open to participants aged 16 Years and older. Per ClinicalTrials.gov, last updated 2026-07-24.
Sponsored by Lydia Flett · Phase 3, Interventional, and Treatment
A multicentre, open label, two-arm, parallel group, pragmatic, randomised controlled trial with internal pilot. A total of 1166 consenting adult patients with cIAI will be recruited and randomised on a 1:1 basis between 28-days antibiotics and standard care antibiotics. Patients will be followed up for 180 days to determine cost effectiveness and the rate of treatment failure in each group.
UK data suggests that current treatment for complicated intra-abdominal infections (cIAIs) results in unacceptably high rates of cIAI relapse and extra-abdominal infection. As a guiding rule, shorter antibiotic durations are important to combat antimicrobial resistance, but this is not true when these shorter courses need repeating and result in more days in hospital. Optimal care for patients should be our primary concern.
The EXTEND trial aims to find out whether a fixed extended duration of 28 days of antibiotics is superior to the current standard duration (typically 7-18 days) based on clinical outcomes and quality of life assessed over 180 days of follow up. Cost effectiveness will also be determined.
A target of 1166 patients will be recruited from ICUs and hospital in-patient wards across approximately 30 NHS trust hospitals. Only patients that are able provide consent (or those with a consultee able to confirm whether the patient would wish to be included in the study) can take part in the trial. They will receive antibiotics as prescribed by their treating clinician, but the duration of treatment will be determined by randomisation. Patients will have equal chance of randomisation to the standard care arm, in which the antibiotic duration will be determined by the treating clinician, or the intervention arm, a fixed duration of 28 days treatment.
Patients (or a personal consultee) will complete a quality of life questionnaire at baseline and 30, 60 and 180 days after randomisation. At follow-up timepoints they will also complete questionnaires on antibiotic use and health care resource use. Hospital notes will be used to collect data on inpatient admissions, relapse and further infections.
The study is Sponsored by the University of Leeds
6,687 studies on the registry are indexed under Infections; 807 are open to participants now.
This study's planned enrollment of 1,166 is above the median of 120 across 4,200 interventional studies indexed under Infections.
Browse Infections studies →This is the only study on the registry with Lydia Flett as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Patients will be included in the trial whether or not they undergo surgical or radiological source control procedures.
* cIAI is defined by the following case definition:
Evidence of pathologic findings at operation
** The first day of effective antibiotic treatment will be determined by the patient's clinical team or clinical research team. Antibiotics that do not count towards these 10 days of effective treatment are:
Previous courses of treatment antibiotics: A previous course is one stopped for 48 hours or more
Exclusion Criteria:
A maximum of 20% of participants entering the trial can have a source of cIAI as the appendix. If 230 patients with appendix as the source are recruited, this will become an exclusion criteria for subsequent patients.
Note: There are absolute exclusions that preclude trial participation. These include: C. difficile infection, Infected necrotic pancreatitis, Concomitant infection requiring ≥4 weeks antibiotic therapy, Treatment with Interleukin-6 Inhibitors, High likelihood of death within 72 hours of randomisation, Limitations in treatment decided before inclusion, Peritoneal dialysis, Previously recruited for the EXTEND trial, Patient with persistent cIAI of more than 6 months duration and a patient with persistent cIAI of more than 6 months duration. If a patient has two intraabdominal infections, the presence of one of the following ineligible infections does not make a patient ineligible if the other cIAI is eligible: Perforated gastric ulcer or duodenal ulcer treated within 24 hours of the onset of symptoms, Traumatic injury to the bowel (including iatrogenic or intra-operative) treated within 12 hours of injury, Uncomplicated diverticulitis, Ineligible cases of appendicitis (see exclusion criteria above), Uncomplicated cholecystitis, Ischemic or necrotic intestine without perforation, Uterine perforation following uterine surgery treated within six hours of injury or cIAI with a low risk of complications.
Clinician decided antibiotic treatment duration
Drug: Antibiotic - standard duration
28 day antibiotic treatment duration
Drug: Antibiotic - fixed-extended-duration
Clinician decided antibiotic and duration of treatment
Clinician decided antibiotic for a fixed duration of 28 days.
Treatment failure within 180 days of randomisation.
For in-patients, treatment failure is defined when a patient meets objective criteria for both inflammation and infection within a 5 day period. Meeting of the criteria for inflammation may precede or follow the date that criteria for infection were met (the first day of an eligible antibiotic treatment course). These criteria are: Criteria for Inflammation * A fever (≥ 37.8 degrees Celsius) or hypothermia (≤36 degrees Celsius), plus * A neutrophilia (\>7.5 x109/L) or neutropaenia (\<1.8 x 109/L), plus * A CRP over 100 mg/L PLUS, criteria for infection * Initiation of a new antibiotic treatment course of ≥ 5 days, or * A change in antibiotic treatment continued for ≥ 5 days, or * Initiation of a new antibiotic treatment, or a change in antibiotic treatment, and death within 5 days. * Bacteraemia with a recognised intestinal pathogen include: Anaerobes (e.g., Bacteroides), Enterobacterales and Streptococcus species. Assessed by blinded outcome committee
Time frame: 180 days
Quality of life (EQ-5D-5L)
Participants will complete the EQ-5D-5L at baseline, and at 30, 90 and 180 days post-randomisation.
Time frame: 180 days
Cost effectiveness
Participants will complete health care resource use questionnaires at 30, 90 and 180 days after randomisation to record activity outside of hospital. Research teams will record data related to expenses as an inpatient.
Time frame: 180 days
Desirability Of Outcome Ranking (DOOR)
Patients will be categorised according to the worst outcome they experience over the 6 months follow up period using a four-level ordinal classification the Desirability Of Outcome Ranking (DOOR). The four levels will be C1 = No treatment failure, C2 = Treatment failure (as for the primary outcome), C3 = Treatment failure associated with sepsis (NEWS 6 in ward-based patients and SOFA 2 in ICU based patients) and C4 = Treatment failure associated with death.
Time frame: 180 days
Number and type of source control procedures
The total number and type of source control procedures measured by reviewing patient notes at 180 days after randomisation. The definition of source control used for this study is any procedure that stops the ongoing contamination of the peritoneal cavity and removes the majority of the contaminated intraperitoneal contents to the extent that no further acute interventions are felt to be necessary. The different types (radiological, surgical) and source control procedures of any type occurring in each randomised group will be compared using a proportional odds model, with fixed effects for allocation, the stratification factors and other prognostic baseline covariates, and random intercepts for study recruitment site.
Time frame: 180 days
Relapse of cIAI
The proportion of patients that experience a relapse of cIAI during the 180 days following randomisation will be reported by randomised group.
Time frame: 180 days
All-cause mortality
All-cause mortality (time to event) measured by reviewing patient notes at 180 days after randomisation. Brief summaries of the total time at risk and number/proportion of participants who died will be presented by randomised group and overall
Time frame: 180 days
Length of hospital stay
Length of hospital stay measured by reviewing patient notes at 180 days after randomisation. Total number of nights in hospital (with death coded as the worst/highest outcome) will be compared using a proportional odds model, with fixed effects for allocation, the stratification factors and other prognostic baseline covariates, and random intercepts for study recruitment site.
Time frame: 180 days
Re-admission
Re-admission measured by reviewing patient notes at 180 days after randomisation. The proportion of participants who are re-admitted to hospital during the 180 days following randomisation, and number of re-admissions per participant will be reported descriptively by randomised group and overall
Time frame: 180 days
C. difficile infection
C. difficile infection measured by reviewing patient notes at 180 days after randomisation. The proportion of patients that experience C. difficile infection during the 180 days following randomisation will be reported by randomised group.
Time frame: 180 days
Anti-microbial resistant (AMR) infections
Anti-microbial resistant (AMR) infections measured by reviewing patient notes at 180 days after randomisation. When standard treatment fails in patients with cIAI, antibiotics are often escalated to one of the carbapenem class of antibiotics. We will therefore use rates of carbapenem prescribing as a surrogate for AMR infections. Participants will undergo passive surveillance for antimicrobial resistant infections (including MRSA, VRE, ESBL and CPE) during the 180 days following randomisation. The proportion of patients that experience each type of antimicrobial infection, number of days receiving carbapenem class antibiotics and the number of antibiotic class switches will be reported descriptively by randomised group and overall.
Time frame: 180 days
Days of antibiotic therapy (in-patient and outpatient)
Days of antibiotic therapy (in-patient and outpatient) including anti-fungal therapy measured by reviewing patient notes and from a questionnaire completed by patients at 180 days after randomisation. The total number of days of anti-microbial therapy (inpatient, outpatient and overall) during the 180 days following randomisation, proportion of total follow up time on anti-microbial therapy, and mortality will be reported descriptively by randomised group and overall.
Time frame: 180 days
Acute kidney injury
Acute kidney injury measured by reviewing patient notes at 180 days after randomisation and defined as: an increase in serum creatinine by ≥ 0.3 mg/dl (≥ 26.5 µmol/l) within 48 hours; or increase in serum creatinine to ≥ 1.5 times baseline, which is known or presumed to have occurred within the prior 7 days; or urine volume \< 0.5 ml/kg/h for 6 hours (KDIGO Clinical Practice Guideline for Acute Kidney Injury). The proportion of patients that experience acute kidney injury during the 180 days following randomisation will be reported by randomised group.
Time frame: 180 days
Complications
Will be measure by reviewing patient notes at 180 days after randomisation.
Time frame: 180 days
Number of days on ventilation and days of renal replacement therapy.
Will be measure by reviewing patient notes at 180 days after randomisation.
Time frame: 180 days
Time to treatment failure
Time to treatment failure and number of episodes of treatment failure.
Time frame: 180 days.
Plan to share: No
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