What is the best course of treatment for a 16-week pregnant patient with a cat bite from a non-vaccinated cat, who also has an allergy to amoxicillin (amoxicillin)?

Treatment of Cat Bite in 16-Week Pregnant Patient with Amoxicillin Allergy

For a 16-week pregnant patient with a cat bite and amoxicillin allergy, use cephalexin 500 mg orally four times daily as first-line therapy, or clindamycin 300-450 mg orally three times daily if there is a history of severe penicillin allergy with anaphylaxis. 1

Antibiotic Selection Algorithm

First-Line: Cephalexin (Preferred for Non-Severe Penicillin Allergy)

• Cephalexin 500 mg orally four times daily is the preferred alternative for penicillin-allergic pregnant patients with moderate-quality evidence supporting safety throughout pregnancy 1
• Cephalosporins like cefazolin are recommended for penicillin-allergic patients except those with immediate hypersensitivity reactions (anaphylaxis, angioedema, respiratory distress, urticaria) 2
• Cefazolin demonstrates 98.37% susceptibility against Pasteurella multocida, the most common pathogen in cat bites 3

Second-Line: Clindamycin (For Severe Penicillin Allergy)

• Clindamycin 300-450 mg orally three times daily is safe for penicillin-allergic pregnant patients with no significant risks of congenital anomalies or preterm delivery 1
• Use clindamycin if the patient has a history of anaphylaxis, angioedema, respiratory distress, or urticaria to penicillins or cephalosporins 2
• Clindamycin provides coverage against both aerobic and anaerobic bacteria commonly found in cat bites 2

Critical Clinical Context for Cat Bites

High Infection Risk

• Cat bites have a 20-80% infection rate, significantly higher than dog bites (3-18%), making prophylactic antibiotics essential 3, 4
• Pasteurella multocida is isolated in over 50% of cat bite wounds and can cause serious infection with severe complications 5
• Approximately 90% of domestic cats carry P. multocida in their oral cavity regardless of age, breed, or lifestyle 3
• Puncture wounds and hand wounds carry the highest infection risk and mandate antibiotic prophylaxis 4

Wound Management

• Copiously irrigate the wound with normal saline using a 20-mL or larger syringe 4
• Explore the wound for tendon or bone involvement and possible foreign bodies 4
• Wounds on the face may be closed if cosmetically favorable, but puncture wounds should generally be left open 4

Pregnancy-Specific Considerations

Safety Profile of Alternatives

• Both cephalexin and clindamycin are safe throughout pregnancy with no increased risk of congenital malformations 1
• Avoid doxycycline during pregnancy (especially first and second trimesters) due to potential fetal risks, despite its effectiveness against P. multocida 2, 1
• Avoid fluoroquinolones entirely during pregnancy 1

Duration of Therapy

• Standard prophylactic treatment duration is 3-7 days for uncomplicated bite wounds 1
• Extend treatment if signs of established infection develop (erythema, purulence, lymphangitis) 2

Additional Essential Management

Rabies Assessment

• Address rabies prophylaxis with any animal bite, even from domestic animals that are often unvaccinated 4
• The cat's vaccination status is unknown in this case, requiring careful risk assessment 4
• Postexposure rabies prophylaxis consists of immune globulin at presentation and vaccination on days 0,3,7, and 14 if indicated 4

Tetanus Immunization

• Verify tetanus immunization status and update if needed 5
• Tetanus toxoid is safe during pregnancy 4

Common Pitfalls to Avoid

• Do not assume all penicillin allergies are equal: Distinguish between mild reactions (rash) versus severe reactions (anaphylaxis) to determine if cephalosporins can be used 2
• Do not delay antibiotic prophylaxis: Cat bites have exceptionally high infection rates and require prompt treatment 3, 4
• Do not use inadequate wound irrigation: Copious irrigation is essential to reduce bacterial load 4
• Do not overlook atypical pathogens: While rare, organisms like Mycobacterium chelonae can cause persistent infection if first-line therapy fails 6