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

  • End date
    Aug 1, 2024
  • participants needed
  • sponsor
    dr. IJM Han-Geurts
Updated on 28 October 2022



Perianal fistula is a burdening disease with an annual prevalence of 2/100.000 in the Dutch population. More than 90% of crypto-glandular fistulas originate from anorectal abscess. Despite adequate drainage of anorectal abscess up to 83% recurs or results in an anal fistula, the majority developing within 12 months. Up till now it is not common practice to routinely administer prophylactic antibiotics to prevent anal fistula development.\


The objective of this trial is to establish if adding antibiotic treatment to surgical drainage of perianal abscess results in less perianal fistulas.

Study design:

The study concerns a double-blind, placebo-controlled, randomized, multicenter trial with treatment of perianal abscess by surgical drainage alone or combined with antibiotic treatment. Patients will be accrued by all participating clinics. The design involves allocation of all appropriate consecutive patients with a primary occurrence of perianal abscess to surgical drainage followed by either antibiotics or placebo. Data will be analyzed on 'intention to treat' basis in case patients are not subjected to the randomized treatment modality.

Study population:

Men and women of 18 years and older who present for the first time with a perianal abscess.

Intervention (if applicable): The antibiotic group receives 7 days of oral metronidazole (500 mg every eight hours) and ciprofloxacin (500 mg every twelve hours) in addition to surgical drainage. The other group receives surgical drainage and postoperatively identical placebo tablets.

Main study parameters/endpoints:

Primary outcome measure is development of a perianal fistula. Secondary outcome measures are quality of life at 12 months measured with the EQ-5D-5L with Dutch rating. Further: in-hospital direct and indirect costs and out-of hospital postoperative costs, need of repeated drainage, patient related outcome (PRO) and clinical outcome measures.

Nature and extent of the burden and risks associated with participation, benefit and group


For this study, patients are asked to take part in a study comparing the addition of antibiotic treatment to surgical drainage of perianal abscess. Patients will not be burdened by extra hospital visits. At baseline participants will complete PRO questionnaires. Also at 1 week and 3, 6 and 12 months participants will fulfill the PRO questionnaires. These will be send to them by email and will take approximately 10 minutes each time.

Condition Perianal Fistula, Perianal Abscess, Drain Abscess
Treatment Placebo, Ciprofloxacin 500 mg, Metronidazole 500 mg
Clinical Study IdentifierNCT05385887
Sponsordr. IJM Han-Geurts
Last Modified on28 October 2022


Yes No Not Sure

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
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)
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If you are confirmed eligible after full screening, you will be required to understand and sign the informed consent if you decide to enroll in the study. Once enrolled you may be asked to make scheduled visits over a period of time.

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