Alvimopan: an oral, peripherally acting, mu-opioid receptor antagonist for the treatment of opioid-induced bowel dysfunction--a 21-day treatment-randomized clinical trial

Early peristalsis following epidural analgesia during abdominal surgery in an extremely low birth weight infant

The inhibiting effect of opioids on intestinal motility is a cause of particular concern in extremely low birth weight (ELBW; birth weight <1000 g) infants with decreased peristalsis. An ELBW infant (birth weight 740 g) born after 26 + 1 week of gestation had an uneventful clinical course during the first few days of life. Sudden deterioration occurred on day 8 with metabolic acidosis, hyperglycemia and frequent apnea with secondary bradycardia. A chest X ray demonstrated the presence of air beneath the diaphragm. Intestinal perforation was suspected and the infant was taken to theater for laparotomy. For pain management, a 22 G epidural catheter was inserted via the caudal approach and threaded to a mid-thoracic level. Epidural ropivacaine was administered intraoperatively and for 48 h postoperatively. The infant was extubated on the following day. Opioids were not required or given at any stage during or after surgery. Peristalsis was present on auscultation as early as 3 h after surgery, the first stool was passed on the same day. Enteral nutrition was resumed early and tolerated well, full enteral feeding was rapidly achieved. Our case shows that the technique of caudal anesthesia is feasible in ELBW infants. We speculate that intestinal motility and establishment of full enteral feedings may be achieved earlier by epidural ropivacaine in cases of abdominal surgery in ELBW infants.

Endogenous opiates and behavior: 2005

This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).

Postoperativer Ileus

Continuous improvements in surgical technique and anaesthesia for ileus have resulted in a significant reduction of perioperative complications. Postoperative outcome of surgical patients is increasingly dependent on the severity of postoperative ileus, which often determines morbidity and length of hospital stay. In the present article we discuss possible variables influencing this disease. Furthermore, means of prevention and therapeutic strategies for postoperative ileus are briefly presented.

Constipation and Diarrhea in Patients with Cancer

Constipation and diarrhea are both common problems in patients with advanced cancer. They are source of major morbidity and distress. Constipation is, overall, more common that diarrhea. Diarrhea may be severe and, in some cases, associated with life-threatening dehydration and electrolyte abnormalities. Indeed, with some of the newer chemotherapy agents, this is a problem seen with increasing frequency. Oncologists must be familiar with the common causes of constipation and diarrhea in cancer patients and the strategies to evaluate and manage these common and distressing symptoms. Both with constipation and diarrhea, there is a differential diagnosis. In many cases, management can be complex and challenging. Approaches to diagnosis, evaluation, and management are reviewed.

Use of novel prokinetic agents to facilitate return of gastrointestinal motility in adult critically ill patients

PURPOSE OF REVIEW

Intolerance of enteral feeding due to impaired gastrointestinal motility is common in critically ill patients. Strategies to prevent or treat gastrointestinal hypomotility include the use of prokinetic agents. Many currently employed prokinetic agents are associated with serious adverse drug reactions. The novel prokinetic agents - alvimopan, tegaserod, and dexloxiglumide - are reviewed.

RECENT FINDINGS

Alvimopan exerts mixed, but generally favorable, effects on restoration of gastrointestinal motility in patients with postoperative ileus. The observation of increased opioid requirements (without increased pain scores) and associated clinical ramifications requires further study. Tegaserod stimulates the peristaltic reflex and improves motility in multiple sites along the gastrointestinal tract. Its efficacy in improving gastrointestinal hypomotility in the critically ill population has not yet been determined. Furthermore, its use has been associated with the development of ischemic colitis and increased requirement for abdominal/pelvic surgery. Dexloxiglumide may be beneficial for improving gastric emptying in critically ill patients, especially those receiving lipid-enriched enteral feeds.

SUMMARY

Novel prokinetic agents show promise for management of gastrointestinal hypomotility in the critically ill population. However, further study is required before these agents can be recommended for use.

Irritable bowel syndrome and chronic constipation: emerging drugs, devices, and surgical treatments

Irritable bowel syndrome (IBS) and chronic constipation (CC) are two of the most common functional disorders of the gut. CC and IBS are estimated to affect up to 20% and 27% of the North American population respectively. Although not life-threatening, CC and IBS can profoundly and negatively affect quality of life and are associated with a significant economic burden related to direct and indirect annual health-care costs. Possible etiologies for IBS and CC include alterations in visceral sensation and gastrointestinal motility. IBS may be caused by disturbances in brain-gut interactions affecting gastrointestinal motility and visceral sensitivity. Research efforts in CC have begun to identify abnormalities in myenteric neurons, alterations in neurotransmitters and their receptors, and incoordination of the muscles of the pelvic floor or anorectum. Both disorders may be influenced by genetic predisposition, environmental factors, and stress. In this article, the safety and efficacy of traditional and emerging therapies for CC and IBS are examined. In addition, their pathophysiology and symptoms are briefly reviewed.

Sodium picosulfate in opioid-induced constipation: results of an open-label, prospective, dose-ranging study

Identification of a safe and effective dose of the laxative sodium picosulfate was investigated in a single-centre, open-label study of 23 patients (age 40-81 years) receiving > or =60 mg/day morphine sulphate and experiencing constipation. A starting dose of 5, 10 or 15 mg sodium picosulfate (1 mg/mL solution) was administered, based on the patient's clinical status at entry and recent requirements for laxatives. Dose titration was permitted (+/-2.5 or 5 mg increments), to a maximum daily dose of 60 mg. Bowel movements, concomitant medication and need for suppositories or enemas were recorded in daily diaries. Sixteen patients withdrew before the end of the planned 14-day treatment period because of deterioration of the underlying condition. Sodium picosulfate was well-tolerated. Serious adverse events were all related to the underlying condition. A satisfactory response (normal stool consistency, not requiring enemas, suppositories or manual evacuation, no significant adverse event) was achieved in 15/20 evaluable patients. The median daily dose to achieve this was 15 mg (range: 5-30 mg) and the median time to first bowel movement after dosing was 11.75 hours (range: 6-22.5 hours). There was no clear relationship between the opioid dose and the optimum dose of sodium picosulfate, confirming that individual dose titration is necessary.

[(3)H]Alvimopan binding to the micro opioid receptor: comparative binding kinetics of opioid antagonists

Alvimopan is a novel peripheral micro opioid antagonist in clinical development for the management of post-operative ileus and opioid-induced bowel dysfunction. We hypothesized that the long duration of action of alvimopan might be related to a slower dissociation rate from the micro opioid receptor compared to other shorter acting antagonists. The dissociation rate of alvimopan from the micro opioid receptor (t(1/2)=30--44 min) was comparable to that of the long acting partial agonist buprenorphine (t(1/2)=44 min), but was slower than those of the antagonists naloxone (t(1/2)=0.82 min) and N-methylnaltrexone (t(1/2)=0.46 min). Also, increases in the apparent affinities and potencies of buprenorphine and alvimopan, but not of naloxone and methylnaltrexone, were observed upon preincubation with the micro opioid receptor. Consistent with its long duration of action, alvimopan has a slow dissociation rate from the micro opioid receptor compared to other shorter acting antagonists and may be more potent if administered prior to dosing with exogenous opioids.

Peripheral opioids for functional GI disease: a reappraisal

Opioids have been used medicinally and recreationally for thousands of years. The clinical use of opioids for gastrointestinal conditions has been limited by central nervous system side effects. A new generation of peripheral opioid receptor ligands free of central nervous system side effects is being developed. Clinical trials with the peripherally acting mu opioid receptor antagonists' alvimopan and N-methylnaltrexone show promise for improving postoperative ileus- and opioid-induced constipation. Likewise, preliminary studies with the peripherally acting kappa opioid agonist fedotozine showed promise in the treatment of irritable bowel syndrome (IBS) and functional dyspepsia. Further studies are on hold presumably due to lack of efficacy in subsequent studies. However, clinical studies are underway for newer kappa opioid agonists such as asimadoline and ADL 10-0101.

Pain management for the hospitalized pediatric patient

Pediatric hospitalists should make pain assessment and treatment a high priority and a central part of their daily practice. Efforts at improving pain treatment in pediatric hospitals should be multidisciplinary and should involve combined use of pharmacologic and nonpharmacologic approaches. Although available information can permit effective treatment of pain for most children in hospitals, there is a need for more research on pediatric analgesic pharmacology, various nonpharmacologic treatments, and different models of delivery of care.