AJVR • Vol 78 • No. 6 • June 2017 695 I t has been clearly established that perioperative ad- ministration of antimicrobials can decrease the inci- dence of SSIs. 1–6 Antimicrobials are recommended for procedures associated with high risk of infection or when postoperative infection would have catastroph- ic consequences on the outcome of surgery. 3,7–9 In humans and other animals, SSI can be a devastating complication, prolong the duration of hospital stay, and dramatically increase medical costs. 5,10,11 There is conficting evidence about the effcacy of prophy- Pharmacokinetics of cefazolin for prophylactic administration to dogs Omar J. Gonzalez DVM Walter C. Renberg DVM, MS James K. Roush DVM, MS Butch KuKanich DVM, PhD Matt Warner MS Received June 20, 2016. Accepted September 6, 2016. From the Departments of Clinical Sciences (Gonzalez, Renberg, Roush) and Anatomy and Physiology (KuKanich, Warner), College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506. Address correspondence to Dr. Gonzalez (ojg10@ yahoo.com). OBJECTIVE To evaluate pharmacokinetics of cefazolin after IV injection of cefazolin (22 mg/kg) and after simultaneous IV and IM injections of cefazolin (total dose, 44 mg/kg) to dogs. ANIMALS 12 adult Beagles. PROCEDURES Dogs (6/group) were assigned to receive a single injection of cefazolin (IV group; 22 mg/kg, IV) or simultaneous injections (IV + IM group; 22 mg/kg, IV, and 22 mg/kg, IM). Interstitial fuid was collected over a 5-hour period by use of ultrafltration probes for pharmacokinetic analysis. RESULTS Mean cefazolin concentration in the interstitial fuid at 1, 1.5, 2, 3, 4, and 5 hours after injection was 39.6, 29.1, 21.2, 10.3, 6.4, and 2.7 µg/mL, respec- tively, for the IV group and 38.3, 53.3, 46.4, 31.7, 19.1, and 8.9 µg/mL, re- spectively, for the IV + IM group. Mean area under the concentration-time curve extrapolated to infnity, maximum concentration, half-life, and time to maximum concentration was 74.99 and 154.16 h•µg/mL, 37.3 and 51.5 µg/mL, 0.96 and 1.11 hours, and 1.28 and 1.65 hours, respectively, for the IV and IV + IM groups. CONCLUSIONS AND CLINICAL RELEVANCE Cefazolin concentrations in interstitial fuid of dogs were maintained at > 4 µg/mL for 4 hours after a single IV injection and for 5 hours after simultane- ous IV and IM injections. Therefore, simultaneous IV and IM administration of cefazolin 30 to 60 minutes before surgery should provide interstitial fuid concentrations effective against the most common commensal organisms (Staphylococcus spp and Streptococcus spp) on the skin of dogs for surgical procedures lasting ≤ 4 hours. (Am J Vet Res 2017;78:695–701) lactic administration of antimicrobials in veterinary medicine; some investigators detected no effect, 12 whereas other investigators detected a decrease in the incidence of SSI for routine clean surgical pro- cedures. 3,13 In a randomized blinded prospective controlled study, 3 the infection rate for control dogs (15.7%) was signifcantly higher than the rate for dogs treated perioperatively with antimicrobials (3.8%). In another study, 13 347 of 365 (95.3%) dogs that underwent orthopedic surgery received antimicrobi- als perioperatively. Only 5 of those 347 (0.01%) dogs developed SSI, whereas 3 of 16 (18.7%) dogs that did not receive antimicrobials perioperatively developed SSI. Investigators of other studies 14–16 have found an overall infection rate between 5.9% and 8.9% for a variety of clean and clean-contaminated procedures, and they have concluded that prophylactic antimi- crobial administration was not required for these procedures. Antimicrobial-resistant bacteria (including multi- drug resistant bacteria), increased risk of hospital- acquired infection, and increased cost of medical care are possible consequences of inappropriate or ABBREVIATIONS AUC Area under the concentration-time curve AUC INF Area under the concentration-time curve extrapolated to infnity Cmax Maximum concentration in interstitial fuid MIC Minimum inhibitory concentration MIC 90 Minimum inhibitory concentration at which 90% of isolates are inhibited SSI Surgical site infection t 1/2 Terminal half-life Tmax Time of the maximum concentration in interstitial fuid UPLC-UV Ultra–high-performance liquid chromatography with UV detection Unauthenticated | Downloaded 10/01/22 05:52 PM UTC