What antibiotic is recommended for a dog bite in a patient with an allergy to Penicillin (PCN) and Cephalosporins?

From the Guidelines

For a dog bite infection in someone allergic to penicillins and cephalosporins, doxycycline is the recommended antibiotic, as it provides excellent activity against Pasteurella multocida, a common and concerning pathogen in dog bites. The typical adult dose is 100mg twice daily for 5-7 days 1. This recommendation is based on the practice guidelines for the diagnosis and management of skin and soft tissue infections by the Infectious Diseases Society of America, which suggests doxycycline as a suitable alternative for patients with a history of hypersensitivity to β-lactams 1.

Some key points to consider when treating dog bite infections include:

• Thorough cleaning of the wound with soap and water
• Updating tetanus prophylaxis if needed
• Seeking immediate medical attention for deep puncture wounds, bites to the face, hands, or joints, or if signs of infection develop
• Considering alternative antibiotics, such as trimethoprim-sulfamethoxazole (TMP-SMX) or clindamycin, in combination with a fluoroquinolone like ciprofloxacin, if doxycycline is not suitable 1

It's essential to note that dog bite infections are typically polymicrobial, containing both aerobic bacteria (like Pasteurella, Streptococcus, and Staphylococcus) and anaerobic organisms, and therefore, antibiotic therapy should be chosen accordingly 1.

In terms of specific antibiotic regimens, the following options can be considered:

• Doxycycline 100mg twice daily for 5-7 days
• TMP-SMX one double-strength tablet twice daily
• Clindamycin 300-450mg three times daily combined with either TMP-SMX or a fluoroquinolone like ciprofloxacin 500mg twice daily 1

From the FDA Drug Label

Clindamycin is indicated in the treatment of serious infections caused by susceptible anaerobic bacteria. Clindamycin is also indicated in the treatment of serious infections due to susceptible strains of streptococci, pneumococci, and staphylococci Its use should be reserved for penicillin-allergic patients or other patients for whom, in the judgment of the physician, a penicillin is inappropriate. Syphilis–early: Patients who are allergic to penicillin should be treated with doxycycline 100 mg, by mouth, twice a day for 2 weeks

For a dog bite in a patient with an allergy to Penicillin (PCN) and Cephalosporins, the recommended antibiotic is Doxycycline or Clindamycin.

• Doxycycline is recommended for syphilis in patients allergic to penicillin 2.
• Clindamycin can be used for serious infections caused by susceptible anaerobic bacteria, streptococci, pneumococci, and staphylococci in penicillin-allergic patients 3.

From the Research

Antibiotic Recommendations for Dog Bites in Patients with Penicillin and Cephalosporin Allergies

• For patients allergic to Penicillin (PCN) and Cephalosporins, alternative antibiotics should be considered for dog bites.
• According to 4, Aztreonam is a monobactam antibiotic that is selectively active against Gram-negative aerobic bacteria and inactive against Gram-positive bacteria, making it a potential option.
• However, Aztreonam is inactive against Gram-positive aerobic bacteria and anaerobes, including Bacteroides fragilis, so it may need to be combined with another antibiotic active against Gram-positive and/or anaerobic bacteria.
• Another option could be to use a cephalosporin with a dissimilar side chain to the offending penicillin, as the cross-reactivity rate is approximately 1% when using first-generation cephalosporins or cephalosporins with similar R1 side chains, as reported in 5.
• It's also important to note that the cross-reactivity between penicillin and cephalosporin drugs occurs in about 2% of cases, as stated in 6, which is less than the 8% reported previously.
• The use of third- or fourth-generation cephalosporins or cephalosporins with dissimilar side chains than the offending penicillin carries a negligible risk of cross allergy, as mentioned in 5.
• Ultimately, the choice of antibiotic should be based on the specific circumstances of the patient and the suspected or confirmed causative organisms of the dog bite infection, and should be made in consultation with a healthcare professional.

Considerations for Penicillin Allergy Evaluation

• Evaluation of penicillin allergy before deciding not to use penicillin or other β-lactam antibiotics is an important tool for antimicrobial stewardship, as stated in 6.
• Many patients report they are allergic to penicillin but few have clinically significant reactions, and the rate of IgE-mediated penicillin allergies is decreasing, as reported in 6.
• Penicillin skin testing can be used to evaluate moderate-risk patients, and carries a negative predictive value that exceeds 95% and approaches 100% when combined with amoxicillin challenge, as mentioned in 6.

Cephalosporin Use in Penicillin-Allergic Patients

• The practice of avoiding cephalosporin administration to penicillin-allergic patients persists despite the low rate of cross reactions between both groups of antibiotics, as discussed in 7 and 5.
• Cefprozil, cefuroxime, cefpodoxime, ceftazidime, and ceftriaxone do not increase the risk of an allergic reaction, as stated in 7.