Empiric Therapy Regimens

Preoperative antibiotic prophylaxis should be given in conjunction with surgery for suspected appendicitis. Antibiotics should be stopped after surgery in patients without perforation. In patients with suspected appendicitis who do not undergo surgery, antimicrobial therapy should be administered for at least 3 days, until clinical symptoms and signs of infection resolve.^{[1, 2, 3, 4, 5]}

Children with uncomplicated appendicitis, without perforation, should receive preoperative, broad-spectrum antibiotics.^[6]For pediatric ruptured appendicitis, subcutaneous antibiotic powder and intravenous (IV) antibiotics can be effective prophylaxis for postoperative intra-abdominal abscess after open appendectomy.^[7]

Antibiotic options in acute appendicitis in those at low risk for adverse outcomes who have community-acquired infection include the following^[8]:

Monotherapy: Ertapenem, moxifloxacin
Combination therapy: Ceftriaxone, cefuroxime, cefotaxime, plus metronidazole; ciprofloxacin or levofloxacin plus metronidazole

Antibiotic options in acute appendicitis in those at high risk for adverse outcomes who have community-acquired of healthcare/hospital-acquired infection include the following^[8]:

Monotherapy: Piperacillin/tazobactam, doripenem, imipenem/cilastatin ± relebactam, meropenem, eravacycline
Combination therapy: Cefepime plus metronidazole, ceftazidime plus metronidazole, ceftolozane/tazobactam plus metronidazole, ceftazidime/avibactam plus metronidazole, aztreonam plus metronidazole plus vancomycin (for those with serious beta-lactam allergies)

See Appendicitis: Avoiding Pitfalls in Diagnosis, a Critical Images slideshow, to help make an accurate diagnosis.

See guidelines regimens below.^[4]

Pediatric acute appendicitis

Monotherapy

Ertapenem: Age 3 months to 12 years – 15 mg/kg IV BID (not to exceed 1 g/day); age 12 years and older – 1 g/day
Meropenem: 20 mg/kg IV every 8 hours
Imipenem/cilastatin: 60-100 mg/kg/day divided every 6 hours
Piperacillin-tazobactam: 200-300 mg/kg/day of piperacillin component

Combination therapy

Ceftriaxone: 50-75 mg/kg/day divided every 12-24 hours plus metronidazole 30-40 mg/kg/day divided every 8 hours
C efotaxime: 150-200 mg/kg/day divided every 6-8 hours plus metronidazole 30-40 mg/kg/day divided every 8 hours
Cefepime: 100 mg/kg/day divided every 12 hours plus metronidazole 30-40 mg/kg/day divided every 8 hours
C eftazidime: 50 mg/kg/day divided every 8 hours plus metronidazole 30-40 mg/kg/day divided every 8 hours
Gentamicin: 3.0-7.5 mg/kg/day divided every 2-4 hours plus (metronidazole 30-40 mg/kg/day divided every 8 hours, or clindamycin 20-40 mg/kg/day divided every 6-8 hours) with or without ampicillin 200 mg/kg/day divided every 6 hours
T obramycin: 3.0-7.5 mg/kg/day divided every 8-24 hours plus (metronidazole 30-40 mg/kg/day divided every 8 hours, or clindamycin 20-40 mg/kg/day divided every 6-8 hours) with or without ampicillin 200 mg/kg/day divided every 6 hours

Adult acute appendicitis: Mild to moderate severity (perforated or abscessed appendicitis)

Monotherapy

Cefoxitin: 2 g every 6 hours or
Ertapenem: 1 g every 24 hours or
Moxifloxacin*: 400 mg every 24 hours* or
Tigecycline: 100 mg initial dose, then 50 mg every 12 hours or
Ticarcillin-clavulanic acid: 3.1 g every 6 hours; FDA labeling indicates 200 mg/kg/day in divided doses every 6 hours for moderate infection and 300 mg/kg/day in divided doses every 4 hours for severe infection

* Because of increasing resistance of Escherichia coli to fluoroquinolones, local population susceptibility profiles and, if available, isolate susceptibility should be reviewed.

Combination therapy

Cefazolin: 1-2 g every 8 hours plus metronidazole 500 mg every 8-12 hours or 1500 mg every 24 hours or
Cefuroxime: 1.5 g every 8 hours plus metronidazole 500 mg every 8-12 hours or 1500 mg every 24 hours or
Cefotaxime: 1-2 g every 6-8 hours plus metronidazole 500 mg every 8-12 hours or 1500 mg every 24 hours or
Ciprofloxacin*: 400 mg every 12 hours plus metronidazole 500 mg every 8-12 hours or 1500 mg every 24 hours or
Levofloxacin*: 750 mg every 24 hours plus metronidazole 500 mg every 8-12 hours or 1500 mg every 24 hours

* Because of increasing resistance of E coli to fluoroquinolones, local population susceptibility profiles and, if available, isolate susceptibility should be reviewed.

Adult acute appendicitis: High-risk severe (severe physiologic disturbance, advanced age, or immunocompromised state)

Monotherapy

Imipenem-cilastatin: 500 mg every 6 hours or 1 g every 8 hours
Meropenem: 1 g every 8 hours
Doripenem: 500 mg every 8 hours
Piperacillin-tazobactam: 3.375 g every 6 hours (dosage may be increased to 3.375 g every 4 hours or 4.5 g every 6 hours)

Combination therapy

Cefepime plus metronidazole: 500 mg every 8-12 hours or 1500 mg every 24 hours or
Ceftazidime: 2 g every 8 hours plus metronidazole 500 mg every 8-12 hours or 1500 mg every 24 hours or
Ciprofloxacin*: 400 mg every 12 hours plus metronidazole 500 mg every 8-12 hours or 1500 mg every 24 hours or
Levofloxacin*: 750 mg every 24 hours plus metronidazole 500 mg every 8-12 hours or 1500 mg every 24 hours

* Because of increasing resistance of E coli to fluoroquinolones, local population susceptibility profiles and, if available, isolate susceptibility should be reviewed.