Effect of alvimopan and codeine on gastrointestinal transit: a randomized controlled study. Alvimopan, a peripherally acting mu-opioid receptor antagonist, compared with placebo in postoperative ileus after major abdominal surgery: results of a randomized, double-blind, controlled study. Effect of an enteric-release formulation of naloxone on intestinal transit in volunteers taking codeine. The safety and efficacy of oral methylnaltrexone in preventing morphine-induced delay in oral-cecal transit time. Reversal of narcotic-induced delay in gastric emptying and paracetamol absorption by naloxone. An investigation of the ability of oral naloxone to correct opioid-related constipation in patients with advanced cancer. Methylnaltrexone prevents morphine-induced delay in oral-cecal transit time without affecting analgesia: a double-blind randomized placebo-controlled trial. A double-blind, randomized, placebo-controlled phase III study of the safety of alvimopan in patients who undergo simple total abdominal hysterectomy. Alvimopan: an oral, peripherally acting, mu-opioid receptor antagonist for the treatment of opioid-induced bowel dysfunction--a 21-day treatment-randomized clinical trial. [The agonist-antagonist nalbuphine prolongs gastro-cecal transit time and induces short-term pain following neuroleptanesthesia using fentanyl. A comparative study using a placebo]. Phase III trial of alvimopan, a novel, peripherally acting, mu opioid antagonist, for postoperative ileus after major abdominal surgery. Methylnaltrexone for reversal of constipation due to chronic methadone use: a randomized controlled trial. Effects of enteric-coated methylnaltrexone in preventing opioid-induced delay in oral-cecal transit time. Enteral naloxone reduces gastric tube reflux and frequency of pneumonia in critical care patients during opioid analgesia. ADL 8-2698, a trans-3,4-dimethyl-4-(3-hydroxyphenyl) piperidine, prevents gastrointestinal effects of intravenous morphine without affecting analgesia. [Effect of enteral naloxone on the incidence of gastritis and esophagitis in mechanically ventilated patients]. Low-dose oral naloxone reverses opioid-induced constipation and analgesia. Effects of subcutaneous methylnaltrexone on morphine-induced peripherally mediated side effects: a double-blind randomized placebo-controlled trial. Alvimopan, a novel, peripherally acting mu opioid antagonist: results of a multicenter, randomized, double-blind, placebo-controlled, phase III trial of major abdominal surgery and postoperative ileus. Epidural naloxone reduces intestinal hypomotility but not analgesia of epidural morphine. Selective postoperative inhibition of gastrointestinal opioid receptors. Opioid-induced delay in gastric emptying: a peripheral mechanism in humans.
background & aims: Opiate bowel dysfunction is a significant clinical problem. Our aim was to evaluate the ability of a peripheral mu-opioid antagonist, alvimopan, to reverse the effect of codeine on gastric, small-bowel, and colonic transit time in healthy volunteers.
                Seventy-four healthy participants (43 women) were randomized in a double-blind, placebo-controlled manner to 1 of 4 groups: alvimopan 12 mg twice daily in the presence and absence of codeine sulfate 30 mg 4 times/day, or codeine or placebo alone. Gastric emptying, small-bowel, and colonic transit were measured by scintigraphy using a 99m-labeled technetium egg meal and 111-labeled indium charcoal delivered to the proximal colon via a delayed-release capsule. The primary end points for colonic transit were geometric center of the colonic counts at 24 hours and time for 50% ascending colon emptying. Analysis of covariance was used to assess the significance of the primary and secondary end points.
                Codeine delayed gastric, small-bowel, proximal, and overall colonic transit (P < .05). Alvimopan reversed codeine's effect on small bowel and colon (ascending colon and overall colonic transit). Alvimopan also accelerated overall colonic transit compared with placebo. Thus, the mean colonic geometric center at 24 hours was 2.33 with placebo/placebo, 3.25 with alvimopan/placebo (P < .05), 1.5 with placebo/codeine (P < .05), and 2.63 with alvimopan/codeine. Alvimopan did not reverse codeine's delay of gastric emptying.
                Alvimopan reverses codeine's inhibitory effect on small-bowel and colon transit and has potential for treatment of opiate bowel dysfunction. Alvimopan alone accelerates colonic transit, suggesting that mu-opiate mechanisms participate in the physiologic control of colonic transit. Alvimopan is a peripherally acting mu-opioid receptor (PAM-OR) antagonist for accelerating gastrointestinal recovery after surgery.
                Patients undergoing open laparotomy (bowel resection, n = 418; hysterectomy, n = 197) were randomized to receive alvimopan 6 or 12 mg or placebo orally > or = 2 h before surgery and then b.i.d. until hospital discharge (up to 7 days). The primary efficacy endpoint was time to gastrointestinal (GI) recovery (measured by toleration of solid food and passage of flatus/stool; GI-3). Secondary endpoints included time to GI-2 recovery (toleration of solid food and passage of stool) and hospital discharge order written (DCO).
                Alvimopan did not significantly accelerate GI-3 compared with placebo [6 mg: hazard ratio (HR) = 1.20, p = 0.080; 12 mg: HR = 1.24, p = 0.038). However, after adjustment for significant covariates (sex/surgical duration), benefits were significant for both doses (6 mg: HR = 1.24, p = 0.037; 12 mg: HR = 1.26, p = 0.028). Alvimopan also significantly accelerated time to GI-2 (6 mg: HR = 1.37, p = 0.008; 12 mg: HR = 1.33, p = 0.018) and DCO (6 mg: HR = 1.31, p = 0.008; 12 mg: HR = 1.28, p = 0.015). Adverse events were similar between groups.
                Alvimopan (6 or 12 mg) accelerates GI recovery and is well tolerated in patients undergoing open laparotomy. Constipation is a common side-effect of opioid therapy; in addition to their analgesic effect, opioids reduce intestinal secretion and motility with an increase in whole-gut transit time. Naloxone, a specific opioid antagonist, reverses these effects but may also cause symptoms of opioid withdrawal in patients on long-term therapy.
                To use an enteric-release formulation, designed to produce a topical effect in the gut, with minimum systemic effects.
                Naloxone 10 mg b.d. and codeine 30 mg b.d. were used with identical placebo capsules in four sets of studies; 12 male volunteers were given the drugs alone and in combination, with a control study involving double placebo, during each of four study periods. Whole-gut transit time was calculated and compared for each treatment period.
                Naloxone, both alone and with codeine, significantly shortened the mean whole-gut transit time compared with the control period, respectively, from 53.1 to 42.1 h (P=0.005) and to 40.7 h (P=0.024). Urgency to defecate was reported by two volunteers on naloxone alone and by three on combination therapy.
                The results show that the naloxone formulation counteracts the effect of codeine on intestinal transit, suggesting that it may have useful clinical applications. Methylnaltrexone is a quaternary opioid antagonist with limited ability to cross the blood-brain barrier that has the potential to antagonize the peripherally mediated gastrointestinal effects of opioids. In recent trials in human volunteers, we demonstrated that intravenous methylnaltrexone prevented morphine-induced changes in gastrointestinal motility and transit, without affecting analgesia. In this study, 14 healthy volunteers were first given three ascending oral doses of methylnaltrexone to obtain safety and tolerance data (phase A study). In phase B, these subjects were then given single-blind oral placebo and intravenous placebo, followed by randomized, double-blind oral placebo and intravenous morphine (0.05 mg/kg) or oral methylnaltrexone (19.2 mg/kg, an established highest and safe dose based on previous administrations of two smaller doses of 0.64 mg/kg and 6.4 mg/kg in phase A) and intravenous morphine (0.05 mg/kg). Oral-cecal transit time was assessed by the pulmonary hydrogen measurement technique after lactulose ingestion. Morphine significantly increased oral-cecal transit time from 114.6 +/- 37.0 minutes (mean +/- SD) to 158.6 +/- 50.2 minutes (p < 0.001). Oral methylnaltrexone (19.2 mg/kg) completely prevented morphine-induced increase in oral-cecal transit time (110.4 +/- 45.0 minutes; not significant compared with baseline; p < 0.005 compared with morphine alone). These sessions were then followed by single-blind evaluations of descending doses of methylnaltrexone. We observed that 6.4 mg/kg oral methylnaltrexone significantly attenuated the morphine-induced delay in oral-cecal transit time (p < 0.005 compared with morphine alone), and a dose-dependent response was obtained. There was no correlation between oral methylnaltrexone effects on the transit time and the drug plasma concentration, suggesting direct preferential luminal effects of oral methylnaltrexone. Oral methylnaltrexone may have a clinical value in the prevention and treatment of constipation induced by long-term opioid use. nan A dose-ranging study of the use of oral naloxone in opioid-related constipation in patients with far-advanced cancer is reported. Naloxone doses were calculated as a percentage of the morphine dose each patient was receiving. Seventeen patients entered the first phase of the study, which had a randomised, double-blind design. Outcome measures were small bowel transit time (SBTT) measured by the lactulose/hydrogen breath test, pain scores and the occurrence of adverse events. One subject was excluded before receiving naloxone. No significant difference between placebo and naloxone occurred in the 14 remaining patients receiving total daily doses of naloxone 10% or less of the 24 h dose of morphine. Two further patients experienced a marked laxative effect with naloxone at 20% of the 24 h dose of morphine. In one of these, SBTT was available and was unchanged from placebo. The other declined to continue with SBTT measurement. Phase two of the study had an open design, in which laxative effects were determined clinically. Naloxone at a maximum dose level of 20% was given to seven patients, up to 40% to two patients and up to 80% to one patient. Four out of the seven patients in the 20% dose level group, and all of the remainder, experienced laxative effects. Two patients experienced symptoms of opioid withdrawal, one of whom also had return of pain. It is concluded that oral naloxone at a daily dose of 20% or more of the prevailing 24 h morphine dose is a potentially valuable therapy for opioid-related constipation. However, opioid withdrawal was observed and it is suggested that initial individual naloxone doses should not exceed 5 mg. Further research is needed into the oral absorption of naloxone, as well as further studies of clinical efficacy and dosing. Methylnaltrexone is a quaternary opioid antagonist with limited ability to cross the blood-brain barrier and the potential to antagonize the peripherally mediated effects of opioids. The effectiveness of methylnaltrexone in preventing morphine-induced changes in gastrointestinal motility and transit without affecting analgesia was evaluated in humans. Twelve healthy volunteers were given intravenous placebo, placebo plus 0.05 mg/kg morphine, or 0.45 mg/kg methylnaltrexone plus 0.05 mg/kg morphine. Oral-cecal transit time was assessed by the pulmonary hydrogen measurement technique, and analgesia was measured with use of the cold-pressor test. Morphine significantly increased oral-cecal transit time from 104.6 +/- 31.1 minutes (mean +/- SD) to 163.3 +/- 39.8 minutes (p < 0.01). Methylnaltrexone prevented 97% of morphine-induced increase in oral-cecal transit time (106.3 +/- 39.8 minutes; not significant compared with baseline; p < 0.01 compared with morphine alone). Methylnaltrexone did not affect the analgesic effect of morphine on both pain intensity and pain bothersomeness ratings. At a higher dose of morphine (0.1 mg/kg), our preliminary results indicated that 0.45 mg/kg methylnaltrexone also prevented the morphine-induced delay in oral-cecal transit time, with no effect on analgesia. Methylnaltrexone may be a useful adjunct to opioids for the relief of opioid-induced constipation. The purpose of this study was to investigate the safety and efficacy of alvimopan, a novel peripherally acting mu-opioid receptor antagonist, in patients who undergo simple total abdominal hysterectomy.
                Women (n = 519) were randomized (4:1) to receive alvimopan 12 mg (n = 413) or placebo (n = 106) > or = 2 hours before the operation then twice daily for 7 days (hospital and home). Adverse events were monitored up to 30 days after the last dose of study drug was administered. Efficacy was assessed for 7 postoperative days.
                Overall, the most common adverse events were nausea, vomiting, and constipation; < 5% of patients discontinued use because of adverse events. Alvimopan significantly accelerated the time to first bowel movement (hazard ratio, 2.33; P <.001). Average time to first bowel movement was reduced by 22 hours, with more frequent bowel movement and better bowel movement quality found in the treatment cohort.
                Alvimopan has a safety profile that is similar to that of placebo and provides significantly improved lower gastrointestinal recovery in women who undergo simple total abdominal hysterectomy. Alvimopan has been shown to reverse the inhibitory effect of opioids on gastrointestinal transit without affecting analgesia. We evaluated oral alvimopan, 0.5 or 1 mg, versus placebo, once daily for 21 days, in 168 patients with opioid-induced bowel dysfunction (OBD) who were receiving chronic opioid therapy (minimum, 1 month) for nonmalignant pain (n = 148) or opioid dependence (n = 20). The primary outcome was the proportion of patients having at least one bowel movement (BM) within 8 hours of study drug on each day during the 21-day treatment period. Averaged over the 21-day treatment period, 54%, 43%, and 29% of patients had a BM within 8 hours after alvimopan 1 mg, 0.5 mg, or placebo, respectively (P < .001). Secondary outcomes of median times to first BM were 3, 7, and 21 hours after initial doses of 1 mg, 0.5 mg, and placebo, respectively (P < .001; 1 mg vs placebo). Weekly BMs and overall patient satisfaction were increased after the 1-mg dose (P < .001 at weeks 1 and 2 vs placebo, and P = .046, respectively). Treatment-emergent adverse events were primarily bowel-related, occurred during the first week of treatment, and were of mild to moderate severity. Alvimopan was generally well tolerated and did not antagonize opioid analgesia. Patients treated with chronic opioid therapy often experience opioid-induced bowel dysfunction as a result of undesirable effects on peripheral opioid receptors located in the gastrointestinal tract. Alvimopan, a novel peripheral opioid mu-receptor antagonist, has demonstrated significant efficacy for the management of opioid-induced bowel dysfunction without compromise of centrally mediated opioid-induced analgesia. Little is known about the effects of mixed opioid analgesics on gastrointestinal propulsion. In 20 patients, nalbuphine (0.1 mg/kg) was given after routine neuroleptanesthesia consisting of 70 micrograms/kg droperidol, 7 micrograms/kg fentanyl, and N2O/O2 (3:1) ventilation, to study its effect on gastrointestinal motility in the postoperative period. For comparison, another group of patients (n = 20) undergoing similar interventions received placebo (0.9% NaCl) at the end of the procedure. Gastrointestinal transit time was determined by measuring the exhaled H2 concentration following gastric lactulose administration. As lactulose is degraded only in the cecum, resulting in the release of hydrogen, the arrival of the polysaccharide at the terminal ileum could thus be determined. Compared to placebo, gastrointestinal transit was significantly longer in patients after nalbuphine (mean transit time 270 min vs 380 min). Pain estimation by visual analogue scale (VAS 0-10) suggested an antagonistic effect at the 10th and 20th min postoperatively, as pain scores in the nalbuphine group were higher when compared to placebo (3.5 vs 1.8 and 2.5 vs 1.4). There was a similar pain score in both groups (1.3 vs 1.4) 30 min after drug administration. However, there was significantly better pain relief after nalbuphine (0.7 vs 1.4 and 0.7 vs 1.1) in the late postoperative period (120th and 240th min). When given after potent opioids, it must be borne in mind that the antagonistic effect of nalbuphine is initially apparent. The agonistic potency of the compound will come into effect around the 30th min post-injection. Delayed gastrointestinal transit after nalbuphine is explained by agonist-like effects on peripheral opioid receptors in the gut. Postoperative ileus presents significant clinical challenges that potentially prolong hospital stay, contribute to readmission, and increase morbidity. There is no approved treatment for postoperative ileus. Alvimopan is a novel, peripherally acting, mu opioid receptor antagonist currently in development for the management of postoperative ileus.
                Patients undergoing partial colectomy or simple or radical hysterectomy were randomized to receive alvimopan 6 mg (n = 152), alvimopan 12 mg (n = 146), or placebo (n = 153) orally 2 hours before surgery and twice daily thereafter until discharge or for up to seven days. The primary efficacy end point, time to return of gastrointestinal function, was a composite measure of passage of flatus or stool and tolerating solid food. Secondary end points included time to the hospital discharge order written. Adverse events were monitored throughout the study.
                Mean time to gastrointestinal recovery was significantly reduced in patients treated with alvimopan 6 mg vs. placebo (hazard ratio = 1.45; P = 0.003), with a smaller reduction seen with alvimopan 12 mg (hazard ratio = 1.28; P = 0.059). Mean time to the hospital discharge order written was significantly accelerated in patients treated with alvimopan 6 mg (hazard ratio = 1.50; P < 0.001). The most common treatment-emergent adverse events across all treatment groups were nausea, vomiting, and hypotension; the incidence of nausea and vomiting was reduced by 53 percent in the alvimopan 12-mg group.
                In patients undergoing major abdominal surgery, alvimopan accelerated gastrointestinal recovery and time to the hospital discharge order written compared with placebo and was well tolerated. Constipation is the most common chronic adverse effect of opioid pain medications in patients who require long-term opioid administration, such as patients with advanced cancer, but conventional measures for ameliorating constipation often are insufficient.
                To evaluate the efficacy of methylnaltrexone, the first peripheral opioid receptor antagonist, in treating chronic methadone-induced constipation.
                Double-blind, randomized, placebo-controlled trial conducted between May 1997 and December 1998.
                Clinical research center of a university hospital.
                Twenty-two subjects (9 men and 13 women; mean [SD] age, 43.2 [5.5] years) enrolled in a methadone maintenance program and having methadone-induced constipation.
                Laxation response, oral-cecal transit time, and central opioid withdrawal symptoms were compared between the 2 groups.
                The 11 subjects in the placebo group showed no laxation response, and all 11 subjects in the intervention group had laxation response after intravenous methylnaltrexone administration (P<.001). The oral-cecal transit times at baseline for subjects in the methylnaltrexone and placebo groups averaged 132.3 and 126.8 minutes, respectively. The average (SD) change in the methylnaltrexone-treated group was -77.7 (37.2) minutes, significantly greater than the average change in the placebo group (-1.4 [12.0] minutes; P<.001). No opioid withdrawal was observed in any subject, and no significant adverse effects were reported by the subjects during the study.
                Our data demonstrate that intravenous methylnaltrexone can induce laxation and reverse slowing of oral cecal-transit time in subjects taking high opioid dosages. Low-dosage methylnaltrexone may have clinical utility in managing opioid-induced constipation. Methylnaltrexone is the first peripheral opioid receptor antagonist. It has the potential to prevent or reverse the peripherally mediated gastrointestinal effects of opioids. In previous human volunteer trials, we demonstrated that oral uncoated methylnaltrexone prevented morphine-induced delay in gastrointestinal transit time.
                This trial consisted of two studies: a pilot study and a controlled study. The lactulose hydrogen breath test was used to measure the oral-cecal transit time.
                In the pilot study with three subjects, an oral dose of 6.4 mg/kg enteric-coated methylnaltrexone effectively reversed the effects of morphine, producing transit times shorter than baseline levels. Subsequently, in the controlled study with another nine subjects, the transit time increased after intravenous morphine administration in all nine subjects, and the lower dose (3.2 mg/kg) of enteric-coated methylnaltrexone completely prevented the morphine-induced change in oral-cecal transit time in all nine subjects. Morphine significantly increased oral-cecal transit time from baseline level of 96.7 +/- 54.1 minutes (mean +/- SD) to 155.0 +/- 53.6 minutes (P = .014). After enteric-coated methylnaltrexone and morphine, the transit time returned to the baseline level (93.3 +/- 56.0 minutes; P = .55 compared with placebo). Plasma concentrations after 6.4 mg/kg and 3.2 mg/kg enteric-coated methylnaltrexone were substantially lower compared with those after 6.4 mg/kg of the uncoated formulation.
                Our results suggest that there is a prevailing direct and local luminal effect of enteric-coated methylnaltrexone and that the enteric-coated formulation exerts its gut pharmacologic actions more efficiently than the uncoated formulation. Opioid analgesia impairs gastrointestinal motility. Enteral administration of naloxone theoretically allows selective blocking of intestinal opioid receptors caused by extensive presystemic metabolism. Therefore, we studied the effect of enteral naloxone on the amount of gastric tube reflux, the frequency of pneumonia, and the time until first defecation in mechanically ventilated patients with fentanyl analgesia.
                Prospective, randomized, double-blinded study.
                University hospital intensive care unit.
                Eighty-four mechanically ventilated, fentanyl-treated patients without gastrointestinal surgery or diseases.
                Patients were assigned to receive 8 mg naloxone or placebo four times daily via a gastric tube during fentanyl administration.
                Thirty-eight patients received naloxone and 43 placebo; three patients were excluded because of protocol violation. Median gastric tube reflux volume (54 vs. 129 mL, p =.03) and frequency of pneumonia (34% vs. 56%, p =.04) were significantly lower in the naloxone group. In both groups, time until first defecation, ventilation time, and length of intensive care unit stay did not differ. There was no difference in fentanyl requirements between the naloxone and the placebo group (7 vs. 6.5 microg/kg/hr, p =.15).
                Our results provide evidence that the administration of enteral opioid antagonists in ventilated patients with opioid analgesia might be a simple-and possibly preventive-treatment of increased gastric tube reflux and reduces frequency of pneumonia. ADL-8-2698 is a novel peripherally restricted opioid antagonist that may selectively prevent opioid-induced gastrointestinal effects without reversing analgesia. Gastrointestinal transit time (lactulose hydrogen breath test) was measured in 14 volunteers with oral and intravenous placebo, oral placebo and intravenous morphine (0.05 mg x kg(-1)), and oral ADL 8-2698 (4 mg) and intravenous morphine (0.05 mg x kg(-1)) in a double blind, cross-over study. Morphine prolonged gastrointestinal transit time from 69 to 103 minutes (P = .005); this was prevented by ADL 8-2698 (P = .004). Postoperatively, 45 patients were randomly assigned in a double-blind fashion to receive ADL 8-2698 (4 mg) or placebo and intravenous morphine (0.15 mg/kg) or to receive oral and intravenous placebo. Analgesia and pupil constriction were measured. Morphine analgesia and pupil constriction were unaffected by ADL 8-2698 and differed from placebo (P < .002). We conclude that ADL 8-2698 prevents morphine-induced increases in gastrointestinal transit time by means of selective peripheral opioid anitagonism without affecting central opioid analgesia. Gastrtis and esophagitis are frequent and severe complications in intensive care patients, mainly caused by increased duodenogastral reflux. Opioids, commonly used in intensive care, are known to impair gastrointestinal (GI) motility which increases retrograd flow of gastric content. In a previous study, we showed that enteral administered naloxone reduces gastric reflux by selectively blocking GI opioid receptors. Therefore, in a subpopulation of these patients we studied the effect of enteral naloxone on the incidence of mucosal injury in opioid-treated, mechanically ventilated patients.
                After IRB approval, mechanically ventilated, fentanyl-treated patients without gastrointestinal surgery or diseases were assigned to receive 8 mg naloxone or placebo four times daily via a gastric tube. Additional inclusion criteria were opioid treatment for at least three days and endoscopy of the upper GI tract. Frequency of gastritis and esophagitis was quantified according to the Savary-Miller Score, and further parameter of GI motility (frequency of propulsive medication, amount of enteral feeding) were measured.
                In four of seventeen patients of the naloxone group (24 %) and 14 of 22 patients of the placebo group (64 %; p = 0.02), esophageal or gastral mucosal injuries were detected. In the naloxone group, gastral reflux as well as need for propulsive medication were significantly lower. Volume of enteral feeding showed an increasing trend in the second half of the study.
                Reduction of esophagogastral mucosal injury and reduced need for procinetic medication suggests an improvement of GI motility by enteral naloxone in fentanyl-treated, mechanically ventilated patients. The most common side effect of opioid therapy is constipation. It is often difficult to treat and is believed to be primarily a peripheral effect. Single large doses of oral naloxone have been shown to be efficacious in reversing opioid-induced constipation. However, they often cause the unwanted side effect of analgesia reversal. This study evaluated the effects on constipation and analgesia of low doses of oral naloxone given three times daily. Patients taking stable doses of opioids with complaints of constipation were recruited for this double-blind, randomized, placebo-controlled study. Patients were given 4 mg or 2 mg of oral naloxone, or placebo, three times daily. Stool frequency and symptoms related to constipation were recorded daily. Patients also recorded the daily amount of analgesics required to maintain pain control. Nine patients were recruited for the study. All the patients who received oral naloxone had some improvement in their bowel frequency. Three of the patients also experienced reversal of analgesia, including one who had complete reversal of analgesia. This study demonstrates that reversal of analgesia still occurred despite dividing the oral naloxone into very low doses relative to the total dose of opioid used. Patients using high doses of opioids appear to be the most vulnerable to the analgesic effect of oral naloxone. Methylnaltrexone, the first peripheral opioid receptor antagonist, has the potential to prevent or reverse opioid-induced peripherally mediated side effects without affecting analgesia. In previous human trials, we demonstrated that intravenous methylnaltrexone prevented morphine-induced delay in gastrointestinal transit time. We also observed that the compound decreased some of the morphine-induced troublesome subjective effects. However, the effects of subcutaneous methylnaltrexone, a more convenient route of administration, have not been evaluated. In this controlled trial, we evaluated the efficacy of subcutanous methylnaltrexone in antagonizing morphine-induced delay in oral-cecal transit time. In addition, opioid-induced unpleasant subjective effects and pharmacokinetics were studied. We observed that in the first group (n = 6) morphine (0.05 mg/kg intravenously) increased the transit time from a baseline level of 85 +/- 20.5 min to 155 +/- 27.9 min (mean +/- S.D., P < 0.01). After 0.1 mg/kg subcutaneous methylnaltrexone plus morphine, the transit time reduced to 110 +/- 41.0 min. In the second group (n = 6), morphine increased the transit time from a baseline level of 98 +/- 49.1 min to 140 +/- 58.2 min (P < 0.01). After 0.3 mg/kg subcutaneous methylnaltrexone plus morphine, the transit time reduced to 108 +/- 59.6 min (P < 0.05 compared with placebo plus morphine). In addition, subcutaneous methylnaltrexone significantly decreased morphine-induced subjective rating changes. Pharmacokinetic data after subcutaneous drug injection were compared to the data obtained from previous intravenous and oral administrations. Our results suggest that subcutaneous methylnaltrexone may have clinical utility in treating opioid-induced constipation and reducing opioid-induced unpleasant subjective symptoms. To demonstrate that alvimopan (6 or 12 mg) accelerates recovery of gastrointestinal (GI) function in patients undergoing laparotomy for bowel resection or radical hysterectomy.
                Postoperative ileus (POI) following laparotomy may increase morbidity and extend hospitalization. Opioids can contribute to the duration of POI. Alvimopan is a novel opioid receptor antagonist in development for the management of POI.
                A total of 510 patients scheduled for bowel resection or radical hysterectomy were randomized (1:1:1) to receive alvimopan 6 mg, alvimopan 12 mg, or placebo orally > or =2 hours before surgery, then twice a day (b.i.d.) until hospital discharge or for up to 7 days. The primary efficacy end point was a composite of time to recovery of upper and lower GI function. An associated secondary end point was time to hospital discharge order written.
                The modified intent-to-treat population included 469 patients (451 bowel resection and 18 radical hysterectomy patients). Time to recovery of GI function was accelerated for the alvimopan 6 mg (hazard ratio [HR] = 1.28; P < 0.05) and 12 mg (HR = 1.54; P < 0.001) groups with a mean difference of 15 and 22 hours, respectively, compared with placebo. The time to hospital discharge order written was also accelerated in the alvimopan 12 mg group (HR = 1.42; P = 0.003) with a mean difference of 20 hours compared with placebo. The incidence of adverse events was similar among treatment groups.
                Alvimopan accelerated GI recovery and time to hospital discharge order written compared with placebo in patients undergoing laparotomy and was well tolerated. Epidural morphine is associated with decreased bowel motility and increased transit time. Low doses of intravenous naloxone reduce morphine-induced pruritus without reversing analgesia, but the effect of epidural naloxone on bowel motility has not been studied. Therefore we evaluated bowel motility and analgesia when naloxone was co-administered with morphine into the epidural space.
                Forty-three patients having combined thoracic epidural and general anesthesia for subtotal gastrectomy were randomly assigned to one of two study groups. All received a bolus dose of 3 mg epidural morphine at the beginning of surgery, followed by a continuous epidural infusion containing 3 mg morphine in 100 ml bupivacaine 0.125% with either no naloxone (control group, n = 18) or a calculated dose of 0.208 microg x kg(-1) x hr(-1) of naloxone (experimental group, n = 25) for 48 hr. We measured the time to the first postoperative passage of flatus and feces to evaluate the restoration of bowel function, and visual analog scales (VAS) for pain during rest and movement. Scores were assessed at 2, 4, 8, 16, 24, 36 and 48 hr postoperatively.
                The experimental group had a shorter time to the first postoperative passage of flatus (5 1.9 +/- 1 6.6 hr vs 87.0 +/- 19.5 hr, P < 0.001 ) and feces (95.3 +/- 25.0 hr vs 132.9 +/- 29.4 hr, P < 0.001). No differences were found in either resting or active VAS between the two groups.
                Epidural naloxone reduces epidural morphine-induced intestinal hypomotility without reversing its analgesic effects. Postoperative recovery of gastrointestinal function and resumption of oral intake are critical determinants of the length of hospital stay. Although opioids are effective treatments for postoperative pain, they contribute to the delayed recovery of gastrointestinal function.
                We studied the effects of ADL 8-2698, an investigational opioid antagonist with limited oral absorption that does not readily cross the blood-brain barrier, on postoperative gastrointestinal function and the length of hospitalization. We randomly assigned 79 patients--including 1 whose surgery was canceled--to receive one capsule containing 1 mg or 6 mg of ADL 8-2698 or an identical-appearing placebo capsule two hours before major abdominal surgery and then twice daily until the first bowel movement or until discharge from the hospital. Data were analyzed for 26 patients in each of the three groups; all received opioids for postoperative pain relief. Observers who were unaware of the group assignments evaluated the outcomes.
                Fifteen patients underwent partial colectomy and 63 underwent total abdominal hysterectomy. Patients given 6 mg of ADL 8-2698 had significantly faster recovery of gastrointestinal function than those given placebo. The median time to the first passage of flatus decreased from 70 to 49 hours (P=0.03), the median time to the first bowel movement decreased from 111 to 70 hours (P=0.01), and the median time until patients were ready for discharge decreased from 91 to 68 hours (P=0.03). Effects in the group that received 1 mg of ADL 8-2698 were less pronounced.
                Selective inhibition of gastrointestinal opioid receptors by an antagonist with limited oral absorption that does not readily cross the blood-brain barrier speeds recovery of bowel function and shortens the duration of hospitalization. Opioids delay gastric emptying, which in turn may increase the risk of vomiting and pulmonary aspiration. Naloxone reverses this opiate action on gastric emptying, but it is not known whether this effect in humans is mediated by central or peripheral opiate antagonism. The importance of peripheral opioid receptor antagonism in modulating opioid-induced delay in gastric emptying was evaluated using methylnaltrexone, a quaternary derivative of the opiate antagonist naltrexone, which does not cross the blood-brain barrier.
                In a randomized, double-blind, crossover placebo-controlled study, 11 healthy volunteers were given either placebo (saline), 0.09 mg/kg morphine, or 0.09 mg/kg morphine plus 0.3 mg/kg methylnaltrexone on three separate occasions before ingesting 500 ml deionized water. The rate of gastric emptying was measured by two methods: a noninvasive epigastric bioimpedance technique and the acetaminophen absorption test.
                The epigastric bioimpedance technique was sufficiently sensitive to detect opioid-induced changes in the rate of gastric emptying. The mean +/- SD time taken for the gastric volume to decrease to 50% (t0.5) after placebo was 5.5 +/- 2.1 min. Morphine prolonged gastric emptying to (t0.5) of 21 +/- 9.0 min (P < 0.03). Methylnaltrexone given concomitantly with morphine reversed the morphine-induced delay in gastric emptying to a t0.5 of 7.4 +/- 3.0 (P < 0.04). Maximum concentrations and area under the concentration curve from 0 to 90 min of serum acetaminophen concentrations after morphine were significantly different from placebo and morphine administered concomitantly with methylnaltrexone (P < 0.05). No difference in maximum concentration or area under the concentration curve from 0 to 90 min was noted between placebo and methylnaltrexone coadministered with morphine.
                The attenuation of morphine-induced delay in gastric emptying by methylnaltrexone suggests that the opioid effect is mediated outside the central nervous system. Methylnaltrexone may have the potential to decrease the side effects of opioid medications, which are mediated peripherally, while maintaining the central analgesia effect of the opioid.