Analgesic effects of tramadol, carprofen or multimodal analgesia in rats undergoing ventral laparotomy

Abstract

In this study, the authors evaluated the analgesic efficacy of tramadol (an opioid-like analgesic), carprofen (a nonsteroidal anti-inflammatory drug) and a combination of both drugs (multimodal therapy) in a rat laparotomy model. The authors randomly assigned rats to undergo either surgery (abdominal laparotomy with visceral manipulation and anesthesia) or anesthesia only. Rats in each group were treated with tramadol (12.5 mg per kg body weight), carprofen (5 mg per kg body weight), a combination of tramadol and carprofen (12.5 mg per kg body weight and 5 mg per kg body weight, respectively) or saline (anesthesia control group only; 5 mg per kg body weight). The authors administered analgesia 10 min before anesthesia, 4 h after surgery or (for the rats that received anesthesia only) anesthesia and 24 h after surgery or anesthesia. They measured locomotor activity, running wheel activity, feed and water consumption, body weight and fecal corticosterone concentration of each animal before and after surgery. Clinical observations were made after surgery or anesthesia to evaluate signs of pain and distress. The authors found that carprofen, tramadol and a combination of carprofen and tramadol were all acceptable analgesia regimens for a rat laparotomy model.

Side effects of pain and analgesia in animal experimentation

“…Thus, the side effect profile of all drugs has to be analyzed carefully. For rodents, several effective multimodal analgesia protocols have been described, with examples including tramadol-carprofen 69 or fentanyltrazodone-paracetamol 70 .…”

Evaluation of buprenorphine hydrochloride Pluronic® gel formulation in male C57BL/6NCrl mice

“…Cannon et al . 3 reported skin lesions in rats given tramadol which was later determined to be due to hyperosmolarity of the product (unpublished data). Buprenorphine has also been reported to have respiratory depression when given at 10 mg/kg doses 62 .…”

“…We incorporated several parameters: feed consumption, body weight, clinical signs, open field activity, and running wheel to evaluate physiologic and behavior changes as previously done by this laboratory 1,3 . Buprenorphine has been shown to decrease feed intake and reduce body weight or weight gain in rodents 4,32,54–60 .…”

“…To accomplish this in those animals undergoing surgery, it is imperative that adequate analgesia be provided. Rodents are commonly used in research and our laboratory has previously evaluated the effectiveness of some analgesic regimes including buprenorphine in rodent surgical models 1–3 .…”

Advances in Exotic Mammal Clinical Therapeutics

“…83 Results of several studies in rats have shown that tramadol can be an effective analgesic for acute pain. [85][86][87][88] In rats, tramadol provided analgesia for osteoarthritis, 85 but its efficacy decreased with increased duration of pain, and its antinociceptive mechanism changed over time, which may partially explain its inconsistent efficacy in patients with chronic pain. 86 Anecdotally, oral tramadol doses of 2 to 10 mg/kg have been well tolerated in rabbits and rats.…”