Antibiotic treatment after draining perianal abscesses

Antibiotic Treatment foLlowing Surgical drAinage of Perianal abScess; the ATLAS Trial, a Double-blind, Placebo-controlled, Randomized Trial

Not applicable Interventional Proctos Kliniek · NCT05385887

This study tests if giving antibiotics after draining perianal abscesses can help prevent the development of perianal fistulas in patients.

Quick facts

PhaseNot applicable
Study typeInterventional
Enrollment298 (estimated)
Ages18 Years and up
SexAll
SponsorProctos Kliniek Academic / other
Drugs / interventionsradiation
Locations11 sites (Tilburg, Noord-Brabant and 10 other locations)
Trial IDNCT05385887 on ClinicalTrials.gov

What this trial studies

This trial investigates whether adding antibiotic treatment to the surgical drainage of perianal abscesses can reduce the incidence of perianal fistulas. It is a double-blind, placebo-controlled, randomized, multicenter trial involving patients with a primary occurrence of perianal abscess. Participants will be randomly assigned to receive either antibiotics or a placebo following their surgical procedure. The study aims to provide evidence on the effectiveness of prophylactic antibiotics in preventing complications after abscess drainage.

Who should consider this trial

Good fit: Ideal candidates for this study are men and women aged 18 years or older who are experiencing a primary perianal abscess.

Not a fit: Patients with a coexisting anorectal fistula or those with recurrent abscesses may not benefit from this study.

Why it matters

Potential benefit: If successful, this study could significantly reduce the recurrence of perianal fistulas in patients who have undergone abscess drainage.

How similar studies have performed: While the use of antibiotics in similar contexts has been explored, this specific approach to preventing perianal fistulas following abscess drainage is relatively novel.

Eligibility criteria

Show full inclusion / exclusion criteria
Inclusion Criteria:

* Men and women aged 18 years or older
* Eligible for e-mail questionnaires
* Sufficient understanding of the Dutch written language (reading and writing)
* Obtained written informed consent

Exclusion Criteria:

* A coexistent anorectal fistula
* Secondary or recurrent anorectal abscess
* Presence of an internal fistula opening
* Any additional surgical procedure performed during the same session
* Previous (peri)anal surgery
* Inflammatory bowel disease
* History of radiation of the pelvic area
* Anorectal malignancy
* Immunodeficiency
* Kidney failure (eGFR \<30ml/min)
* Valvular heart disease
* Pregnancy or lactation
* Postoperative antibiotic prophylaxis indicated for another reason
* Immunosuppressive medication at the time of surgery
* Allergy to metronidazole or ciprofloxacin
* Not able or trouble with swallowing pills
* Concomitant use of:

  * Tizanidine, theophylline, clozapine, olanzapine, pirfenidone, carbamazepine, agomelatine (these are all CYP1A2 substrates, ciprofloxacin is an inhibitor)
  * Amiodarone, erythromycin, sotalol, azithromycin, citalopram, escitalopram, flecainide, fluconazole, haloperidol \>5mg/day, methadone, ondansetron (concerning prolonged QT interval in combination with ciprofloxacin)
  * Lithium (can cause toxic levels with metronidazole)
  * Lopinavir/ritonavir, ritonavir capsules, temsirolimus, disulfiram (antabuse), mebendazole (can cause serious side effects, confusion and psychosis in combination with metronidazole)
  * Corticosteroids (in combination with ciprofloxacin higher risk of tendinitis and tendon rupture).

Where this trial is running

Tilburg, Noord-Brabant and 10 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
Conditions Perianal FistulaPerianal AbscessDrain Abscessantibioticsantibiotic treatmentperianal fistulaperianal abscessdrainage of abscess
Last reviewed 2026-06-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.