The surgical stress response and resulting physiologic changes can lead to postoperative complications and negatively impact animal welfare. Although appropriate pain management is crucial to reduce the pain and stress response to surgery, analgesic choice can significantly affect bone and wound healing. This review aims to summarize data from rat and mouse studies and to provide recommendations for integrating analgesia into orthopedic and wound healing models in these species. Data from other species, such as humans, rabbits and other rodents, is included, where available. From these data, we conclude that for orthopedic surgical models, opioids, local anesthetics and dissociative agents have minimal impact on fracture healing; cyclooxygenase 2 (COX2) selective nonsteroidal antiinflammatory drugs (NSAID) may be used in the shortterm; and steroids should be avoided. For wound healing models, short-term systemic or topical opioids have negligible impact on wound healing; NSAID or local anesthetics may be used short-term; and systemic steroids should be avoided. Alternative analgesics such as tramadol, gabapentin, ketamine, and acetaminophen warrant consideration and further evaluation for both orthopedic and wound healing models. In all cases, researchers and veterinarians should work together to determine the appropriate analgesic plan to minimize pain, as well as to minimize unwanted effects on the orthopedic and wound healing models themselves.

Appropriate analgesia is a crucial part of rodent postoperative and postprocedural pain. Providing appropriate analgesia is an ethical obligation, a regulatory requirement, and an essential element of obtaining quality scientific results and conducting reproducible data. Meeting these requirements is facilitated by practical, efficient and safe delivery methods for providing analgesia. Over the last decade, long-acting analgesics have gained widespread use in research animal medicine to avoid or treat postoperative or postprocedural pain while minimizing handling-related time and stress. Long-acting formulations of analgesics suitable for rodents are available for opioids, NSAIDs, and local anesthetics. The goal of this review is to summarize the currently available long-acting formulations of analgesics for rodents and to provide recommendations to veterinarians and researchers regarding their use.

Alfaxalone is an injectable anesthetic agent that is used in veterinary medicine for general anesthesia. We evaluated the safety and efficacy of alfaxalone delivered through continuous rate infusion by comparing ketamine–xylazine–alfaxalone (KXA) anesthesia with ketamine–xylazine (KX) anesthesia in Sprague–Dawley rats. Anesthesia was induced in male and female rats by using subcutaneous KX. After induction, rats in the KXA group received alfaxalone (10 mg/kg/h IV) for 35 min, whereas rats in the KX group did not receive alfaxalone. At the end of the trial, alfaxalone was discontinued, and xylazine was reversed in all rats by using atipamezole. Throughout anesthesia, we assessed forepaw withdrawal reflex (FPWR), hindpaw withdrawal reflex (HPWR), response to surgical stimulation, heart rate, respiratory rate, SpO₂, body temperature, and time to standing. KXA produced a reliable surgical plane of anesthesia, as evidenced by the loss of both FPWR and HPWR and lack of response to surgical stimulation in all 16 rats, whereas only 6 of the 16 rats in the KX group lost HPWR. No rat in the KXA group regained a paw withdrawal reflex during alfaxalone administration, whereas 3 of the 12 rats (25%) in the KX group that reached a surgical plane of anesthesia exited that plane within the 35-min timeframe. Neither heart rate, respiratory rate, SpO₂, body temperature, nor time to standing differed between KXA and KX groups; and there were no sex-associated differences in anesthesia response. These results indicate that alfaxalone (10 mg/kg/h IV) delivered through continuous rate infusion, in combination with ketamine and xylazine, provides a safe, prolonged, and reliable surgical plane of anesthesia in rats.