The effects of tramadol and fentanyl on gastrointestinal motility in septic rats

Effects of Midazolam and Midazolam-Butorphanol on Gastrointestinal Transit Time and Motility in Cockatiels (Nymphicus hollandicus)

Positive contrast gastrointestinal (GI) studies are performed frequently in avian medicine to identify GI obstruction, luminal distension, and intracoelomic mass effects. However, repeated manual restraint and radiographic positioning may result in a stress-response and associated morbidity in birds, which can be attenuated by administration of sedative drugs. In mammals, many sedative drugs have been shown to affect GI transit times and motility. In this randomized, blinded, controlled prospective study, the effects of midazolam (M; 6 mg/kg IM) and midazolam-butorphanol (MB; 3 mg/kg each IM) on GI transit times were evaluated in 12 healthy cockatiels (Nymphicus hollandicus). Iohexol (20 mL/kg) was administered by crop gavage 15 minutes after induction of sedation, and fluoroscopic images were obtained at different time points. Both sedation protocols significantly affected GI transit times and motility, and the MB protocol had more pronounced effects. Overall median (range) GI transit times were 60 (30-120), 90 (30-120), and 120 (120-180) minutes for the control, M, and MB groups, respectively. Ventricular contractions were markedly reduced with both sedation protocols, while esophageal boluses were reduced only in the MB group. Visualization of the GI tract after iohexol administration was graded highest in the control group and poorest in the MB group. Our results show that commonly used sedative drugs have significant effects on GI transit time and motility in birds. Therefore, GI transit times obtained in sedated birds should not be compared to available reference transit times obtained from unsedated animals.

Comparison of In Vitro Effects of Opioid Analgesics on Spontaneous Proximal and Distal Colon Contractions in Healthy Rats and Rats with Peritonitis

Objective

The goal of this study was to investigate and compare the effects of opioids on proximal and distal colon contractions in normal rats and rats with peritonitis, with and without the presence of naloxone in the environment.

Methods

The study was approved by Cumhuriyet University Ethics committee. In this study, 16 Wistar Albino male rats were used. Rats were divided into two groups. Peritonitis was induced using a cecum ligation and perforation method, 24 h before the tissues of rats in the peritonitis group were collected, and sham surgery was performed 24 h before the tissues of rats in the control group were collected. Twenty-four hours after the surgery, rats' organs were harvested and hung in organ baths. Concentration-dependent inhibitory effects of morphine and meperidine on spontaneous intestinal movements were observed. Any differences between the groups were tested using the Kruskal-Wallis test, and any differences between the groups were tested using the Tukey test.

Results

No significant difference was observed between the proximal and distal colon smooth muscle contraction responses in both groups after 80 mM Potassium Chloride (KCl) injection (p>0.005). In the peritonitis group, amplitudes and frequencies of spontaneous contractions in proximal and distal colon significantly increased (p<0.05). Drugs decreased the amplitude and frequency responses in the control group (p<0.05). In the peritonitis group, whereas morphine decreased the amplitude and frequency responses in comparison with the control group (p<0.05), meperidine did not cause any significant changes (p>0.05). In both groups, adding naloxone to the organ baths before adding opioids completely blocked the morphine's inhibitory effect on the amplitude and frequency (p<0.05), but it could not completely block the inhibition caused by meperidine.

Conclusion

Morphine and meperidine exhibit an inhibitory effect on the intestinal motility in both groups. This effect can be blocked by naloxone completely in morphine, and partially in meperidine.

Analgesic opioid dose is an important indicator of postoperative ileus following radical cystectomy with ileal conduit: experience in the robotic surgery era

PURPOSE

Postoperative ileus (POI) is common following bowel resection for radical cystectomy with ileal conduit (RCIC). We investigated perioperative factors associated with prolonged POI following RCIC, with specific focus on opioid-based analgesic dosage.

MATERIALS AND METHODS

From March 2007 to January 2013, 78 open RCICs and 26 robot-assisted RCICs performed for bladder carcinoma were identified with adjustment for age, gender, American Society of Anesthesiologists grade, and body mass index (BMI). Perioperative records including operative time, intraoperative fluid excess, estimated blood loss, lymph node yield, and opioid analgesic dose were obtained to assess their associations with time to passage of flatus, tolerable oral diet, and length of hospital stay (LOS). Prior to general anaesthesia, patients received epidural patient-controlled analgesia (PCA) consisted of fentanyl with its dose adjusted for BMI. Postoperatively, single intravenous injections of tramadol were applied according to patient desire.

RESULTS

Multivariate analyses revealed cumulative dosages of both PCA fentanyl and tramadol injections as independent predictors of POI. According to surgical modality, linear regression analyses revealed cumulative dosages of PCA fentanyl and tramadol injections to be positively associated with time to first passage of flatus, tolerable diet, and LOS in the open RCIC group. In the robot-assisted RCIC group, only tramadol dose was associated with time to flatus and tolerable diet. Compared to open RCIC, robot-assisted RCIC yielded shorter days to diet and LOS; however, it failed to shorten days to first flatus.

CONCLUSION

Reducing opioid-based analgesics shortens the duration of POI. The utilization of the robotic system may confer additional benefit.

Physiology, signaling, and pharmacology of opioid receptors and their ligands in the gastrointestinal tract: current concepts and future perspectives

Opioid receptors are widely distributed in the human body and are crucially involved in numerous physiological processes. These include pain signaling in the central and the peripheral nervous system, reproduction, growth, respiration, and immunological response. Opioid receptors additionally play a major role in the gastrointestinal (GI) tract in physiological and pathophysiological conditions. This review discusses the physiology and pharmacology of the opioid system in the GI tract. We additionally focus on GI disorders and malfunctions, where pathophysiology involves the endogenous opioid system, such as opioid-induced bowel dysfunction, opioid-induced constipation or abdominal pain. Based on recent reports in the field of pharmacology and medicinal chemistry, we will also discuss the opportunities of targeting the opioid system, suggesting future treatment options for functional disorders and inflammatory states of the GI tract.

The role of experimental models in developing new treatments for irritable bowel syndrome

Irritable bowel syndrome (IBS) is characterized by chronic, recurrent abdominal pain and altered bowel habits and is currently defined by symptom criteria and the absence of detectable organic disease. The underlying pathophysiology remains incompletely understood. Despite considerable efforts by the scientific community and the pharmaceutical industry to develop novel pharmacological treatments aimed at chronic visceral pain, the traditional approach to identifying and evaluating novel drugs for this target have largely failed to translate into effective IBS treatments. However, several novel drugs aimed at normalizing bowel movements have produced clinical effects, not only on the primary target, but also on pain and discomfort. While some of the commonly used experimental animal models for the pain dimension of IBS have some face and construct validity, the predictive validity of most of the models is either unknown, or has been disappointing. A reverse translational approach is proposed, which is based on identification and characterization of brain endophenotypes in patients, followed by translation of these endophenotypes for pharmacological studies in rodent models.