Randomized, Double-Blind, Placebo-Controlled Trial of Metronidazole and Ciprofloxacin in Reducing Perianal Fistula Formation Post-Perianal Abscess Drainage

The primary objective of this trial is to determine whether the addition of **antibiotic** treatment to surgical drainage of a **perianal abscess** reduces the incidence of perianal fistulas. This is clinically significant as perianal fistulas can lead to chronic discomfort, recurrent infections, and may require further surgical interventions, impacting patient quality of life and healthcare resources.

Secondary objectives include evaluating the following aspects:

• Quality of life
• Costs and cost-effectiveness
• Recurrent abscesses
• Repeated drainage
• Patient-reported outcome measures
• Complications
• Clinical outcomes

The clinical trial focuses on individuals diagnosed with **perianal abscess**. The study population includes both male and female adults over the age of 18, who are capable of understanding and responding to email questionnaires in Dutch. Participants must have provided written informed consent. The trial does not involve a vulnerable population. The sponsor has not provided information regarding the total number of participants. Selection criteria emphasize the ability to comprehend Dutch written language, ensuring effective communication throughout the study. The trial aims to determine the efficacy of adding antibiotic treatment to surgical drainage in reducing the incidence of perianal fistulas.

The clinical trial is designed to evaluate the efficacy of adding antibiotic treatment to surgical drainage in reducing the incidence of perianal fistulas following a **perianal abscess**. This study is a **randomized**, **double-blind**, **placebo-controlled** trial, ensuring that neither the participants nor the researchers know who is receiving the active treatment or placebo, thus minimizing bias. The trial is expected to run from December 2021 to July 2026, with participant involvement lasting up to one year. The primary endpoint is the development of a perianal fistula within one year, while secondary endpoints include quality of life, cost-effectiveness, and other health outcomes.

Participants will undergo a series of study visits, beginning with an inclusion (screening) visit to confirm eligibility based on criteria such as age over 18, ability to complete email questionnaires, and proficiency in Dutch. Following successful screening and informed consent, participants will be randomly assigned to receive either **Metronidazole**, **Ciprofloxacin**, or a placebo, all administered orally in the form of film-coated tablets. The maximum treatment period is seven days, with a daily dose not exceeding 2400 mg for Metronidazole and 1500 mg for Ciprofloxacin. Follow-up visits will be scheduled to monitor the participants' health status, adherence to the treatment regimen, and any adverse events. The end-of-study visit will assess the primary and secondary endpoints, including the presence of perianal fistulas and overall health outcomes.

Participants are expected to remain in the study for the full duration unless specific conditions necessitate early termination. These conditions include significant adverse reactions to the medication, withdrawal of consent, or any other medical reasons deemed necessary by the study investigators. The trial aims to provide valuable insights into the therapeutic benefits of antibiotics in conjunction with surgical intervention for perianal abscesses, potentially influencing future treatment guidelines.

The clinical trial involves the administration of **Metronidazole** as an experimental medication. The product, marketed as Metronidazol Aurobindo 500 mg, is provided in the form of **film-coated tablets**. The active substance, metronidazole, is of chemical origin. The medication is administered orally with a maximum daily dose of 2400 mg and a total maximum dose of 16800 mg over a treatment period of 7 days. The pharmaceutical product is manufactured by Aurobindo Pharma B.V. and is authorized for use in the Netherlands under the marketing authorization number RVG 08652. Participant compliance with the dosing schedule will be monitored throughout the trial.

Another experimental medication used in the trial is **Ciprofloxacin**, marketed as Ciprofloxacine Teva 500 mg. This medication is also provided in the form of film-coated tablets and is administered orally. The active substance, ciprofloxacin, is of chemical origin. The maximum daily dose is 1500 mg, with a total maximum dose of 10500 mg over a 7-day treatment period. The product is manufactured by Teva Pharma Belgium N.V./S.A and is authorized for use in Belgium with the marketing authorization number BE291453. Compliance with the dosing regimen will be closely monitored to ensure adherence.

The trial also includes the use of placebo tablets, manufactured by Tiofarma B.V., to serve as a comparator treatment. The placebo is designed to match the appearance of the active medications but contains no active pharmaceutical ingredients. The placebo is used to maintain the double-blind nature of the study, ensuring that neither the participants nor the investigators are aware of the treatment assignments. The administration schedule for the placebo will mirror that of the active medications to maintain consistency in the trial protocol.

The efficacy of the clinical trial titled "Antibiotic treatment following surgical drainage of perianal abscess: a double-blind, placebo-controlled, randomized trial" will be assessed using both primary and secondary endpoints. The primary endpoint is the development of a **perianal fistula** within one year. This will be the main measure to determine the effectiveness of adding antibiotic treatment to surgical drainage.

Secondary endpoints include a variety of parameters to provide a comprehensive evaluation of the treatment's impact. These parameters are: quality of life at 12 months, costs and cost-effectiveness, need for repeated drainage, recurrent abscess, complications, patient-reported outcomes measures, length of hospital stay, readmissions, and time until return to work. These endpoints will be measured and collected at specified intervals throughout the trial duration, with a focus on capturing both clinical and patient-centered outcomes.