Effect of prophylactic cefalexin treatment on the development of bacterial infection in acute radiation-induced dermatitis in dogs: a blinded randomized controlled prospective clinical trial.

BACKGROUND: Acute radiation-induced dermatitis (ARID) is a common sequela of radiation therapy and carries the risk of secondary bacterial skin infection. No standard of care exists for managing canine ARID and evidence-based guidelines are lacking; however, prophylactic use of antibiotics is common.

HYPOTHESIS/OBJECTIVES: To evaluate the impact of prophylactic cefalexin on the prevalence and severity of bacterial infection in canine ARID.

ANIMALS: Seventeen dogs treated with definitive-intent radiotherapy.

METHODS: All dogs were treated with definitive-intent radiation therapy (48-57.5 gray) targeted to the skin surface. Dogs were randomized to receive either prophylactic cefalexin (22 mg/kg twice daily) beginning halfway through the prescribed radiotherapy course (cohort A) or to serve as controls (cohort B). Aerobic skin cultures and surface cytological evaluation were performed at first onset of moist desquamation and one week following completion of radiation therapy. Skin toxicity grading and owner quality of life (QoL) questionnaires were performed weekly. The rate of infection, multidrug resistance status, toxicity severity and QoL between cohorts were compared.

RESULTS: Staphylococcus schleiferi and S. pseudintermedius were the most frequent bacterial agents isolated in both cohorts. There was no significant difference in prevalence of bacterial infection or overall QoL between cohorts at either time point; however, multidrug-resistant infections were significantly increased in cohort A versus cohort B. Clinician- and client-perceived severity of toxicity was significantly greater and median duration of moist desquamation was significantly longer in cohort A than cohort B.

CONCLUSIONS AND CLINICAL IMPORTANCE: Prophylactic use of cefalexin for management of canine ARID is not recommended.