What are the preferred antibiotics for perianal abscess?

From the Guidelines

For perianal abscesses, the preferred antibiotic treatment typically includes broad-spectrum coverage with agents effective against mixed aerobic and anaerobic bacteria, with amoxicillin-clavulanate being a common choice for outpatient management. First-line treatment is surgical incision and drainage, with antibiotics generally reserved for patients with systemic symptoms, immunosuppression, or extensive cellulitis. When antibiotics are indicated, the choice of antibiotic should be based on the severity of the infection and the patient's underlying health status.

Key Considerations

• The polymicrobial nature of perianal abscesses, which typically contain Escherichia coli, Bacteroides species, and other enteric and skin flora, should be taken into account when selecting an antibiotic regimen 1.
• Antibiotics should complement, not replace, proper surgical drainage, which remains the cornerstone of treatment for perianal abscesses.
• For patients with systemic signs of infection, immunocompromised patients, or those with significant cellulitis, empiric broad-spectrum antibiotic therapy with coverage of Gram-positive, Gram-negative, and anaerobic bacteria is recommended 1.

Antibiotic Options

• Amoxicillin-clavulanate (875/125 mg orally twice daily for 5-7 days) is often the preferred choice for outpatient management.
• Alternative options include trimethoprim-sulfamethoxazole (1-2 DS tablets twice daily) plus metronidazole (500 mg orally three times daily), or clindamycin (300-450 mg orally four times daily) for patients with penicillin allergies.
• For more severe infections requiring intravenous therapy, options include piperacillin-tazobactam (3.375 g IV every 6 hours), ampicillin-sulbactam (3 g IV every 6 hours), or ceftriaxone (1-2 g IV daily) plus metronidazole (500 mg IV every 8 hours). It's worth noting that the ECCO statement 1 mentions the use of metronidazole and/or ciprofloxacin in combination with seton placement for symptomatic simple perianal fistulas, but this is a different clinical scenario than perianal abscesses.

From the FDA Drug Label

1. 4 Complicated Intra-Abdominal Infections Moxifloxacin hydrochloride tablets are indicated in adult patients for the treatment of Complicated Intra-Abdominal Infections (cIAI) including polymicrobial infections such as abscess caused by susceptible isolates of Escherichia coli, Bacteroides fragilis, Streptococcus anginosus, Streptococcus constellatus, Enterococcus faecalis, Proteus mirabilis, Clostridium perfringens, Bacteroides thetaiotaomicron, or Peptostreptococcus species [see CLINICAL STUDIES (14.6)].

Table 18: Clinical Success Rates in Patients with Complicated Intra-Abdominal Infections Study Moxifloxacin Hydrochloride n/N (%) Comparator n/N (%) 95% Confidence Interval North America (overall) 146/183 (79.8%) 153/196 (78.1%)(-7.4%, 9.3%) Abscess 40/57 (70.2%) 49/63 (77.8%)

The preferred antibiotics for peri-anal abscess are not explicitly stated in the provided drug labels. However, moxifloxacin hydrochloride is indicated for the treatment of complicated intra-abdominal infections, including abscesses.

• Moxifloxacin has a clinical success rate of 70.2% for abscesses in the North America study.
• The comparator has a clinical success rate of 77.8% for abscesses in the North America study. It is essential to note that the choice of antibiotic should be based on the specific circumstances of each patient and the susceptibility of the causative organisms. 2 2

From the Research

Preferred Antibiotics for Peri-anal Abscess

• The use of antibiotics in the treatment of peri-anal abscesses is a topic of ongoing research, with some studies suggesting that antibiotics may help prevent the development of anal fistulas 3, 4.
• A systematic review and meta-analysis found that antibiotic therapy following incision and drainage of anorectal abscesses was associated with a 36% lower odds of fistula formation 3.
• A randomized single-blind clinical trial found that postoperative prophylactic antibiotic therapy, including ciprofloxacin and metronidazole, played an important role in preventing fistula in-ano formation 4.
• Another study found that ciprofloxacin was well tolerated and may be effective in treating perianal fistulas, although the differences were not significant in the pilot study 5.
• The ATLAS trial is currently investigating whether the addition of antibiotics (ciprofloxacin and metronidazole) to surgical drainage of a perianal abscess is beneficial compared with surgical drainage alone 6.

Antibiotic Regimens

• The most commonly studied antibiotic regimens for peri-anal abscesses include ciprofloxacin and metronidazole 6, 5, 4.
• The duration of antibiotic therapy varied in the studies, ranging from 5-10 days 3, 4.
• The choice of antibiotic regimen and duration of therapy may depend on various factors, including the severity of the abscess, the presence of underlying conditions, and the risk of antibiotic resistance.

Clinical Guidelines

• The SICCR position statement provides evidence-based recommendations for the evaluation and management of perianal abscess and anal fistula, although it does not specifically address the use of antibiotics in the prevention of anal fistulas 7.
• Further research is needed to fully clarify the role, duration, and type of antibiotics best suited for postoperative prevention of fistula following drainage of anorectal abscesses 3, 4.