Efficacy of prophylactic oral erythromycin to improve enteral feeding tolerance in preterm infants: a randomised controlled study

INTRODUCTION

Enteral feeding intolerance is a major problem in preterm infants. This study evaluated the safety and efficacy of prophylactic low-dose oral erythromycin, a motilin agonist, as a prokinetic agent in reducing the incidence of this problem.

METHODS

From February to May 2008, a prospective randomised controlled trial was conducted at the Isfahan University of Medical Sciences, Isfahan, Iran. 70 uncomplicated preterm infants (28-34 weeks' gestation) weighing 1,000-1,500 g were randomly assigned to either a case group receiving low-dose oral erythromycin (6 mg/kg/day, in four doses over ten days) or a control group (n is 35 in each group) until they were fully fed enterally (150 ml/kg/day). Gavage feeding of the mother's milk was started within the first three days of life, and erythromycin was given simultaneously. The time taken to reach full enteral feeding and the total duration of feeding interruption due to intolerance were compared.

RESULTS

The time taken to reach full enteral feeding was significantly shorter in the erythromycin group than the control group (10.11 +/- 2.51 versus 12.71 +/- 5.76 days, p is 0.01). In the control group, the mean duration of feeding interruption was significantly longer (84.00 +/- 62.58 versus 32.57 +/- 11.93 hours, p is 0.005) and more episodes of abdominal distention and significant gastric residue were also noted (p less than 0.05). No infant in the erythromycin group developed cardiac arrhythmias or pyloric stenosis.

CONCLUSION

The prophylactic use of erythromycin may be warranted in very low birth weight infants, provided the efficacy and safety of the drug can be confirmed in further studies.

Prokinetic drugs for feed intolerance in critical illness: current and potential therapies

Studies consistently show that nasogastric nutrition delivers only about 60% of nutritional goals in critically ill patients. The predominant reason is abnormal gastric motility, leading to delayed gastric emptying, which is evident clinically as large gastric residual volumes. Delayed gastric emptying occurs in about 50%-60% of critically ill patients who are fed enterally and can result in malnutrition. Furthermore, delayed gastric emptying may increase the risk of aspiration of gastric contents. Recent research has improved our understanding of the complex abnormalities of gastric motor function that underlie delayed gastric emptying in the critically ill. Feed intolerance can be treated with prokinetic drugs and/or by the placement of postpyloric feeding catheters. The place of prokinetic agents in the treatment of feed intolerance is as yet unclear, but current evidence supports the administration of erythromycin combined with metoclopramide as first-line therapy. Other novel drugs, such as methylnaltrexone, mitemcinal, ghrelin agonists and dexloxiglumide, have potential advantages over these agents but require further investigation before widespread clinical use.

Clinical trial: effect of mitemcinal (a motilin agonist) on gastric emptying in patients with gastroparesis - a randomized, multicentre, placebo-controlled study

BACKGROUND

Mitemcinal is an orally active motilin agonist that could potentially improve gastric emptying.

AIM

To investigate the effect of mitemcinal on gastric emptying in patients with idiopathic and diabetic gastroparesis.

METHODS

In a randomized, double-blind design, 106 patients were randomized into four dosing regimens (22 to placebo and 21 each to mitemcinal 10 mg, 20 mg, 30 mg bid or 20 mg tid) for 28 days. A standardized scintigraphic gastric emptying test was performed at screening and again after completing the 4-week protocol.

RESULTS

All doses of mitemcinal showed prokinetic activity. A significant improvement in meal retention at 240 min was noted even in the lowest dose group with the greatest improvement observed with 30 mg bid group (75% vs. 10% in placebo group). Diabetic patients responded better than the idiopathic subgroup. In diabetic patients, blood glucose at 1 h after a meal showed dose-dependent elevation. Although gastroparetic symptoms improved with both mitemcinal and placebo, the prominent placebo effect was not statistically exceeded by mitemcinal. Baseline scintigraphy results exhibited no clear correlation between the severity of gastroparetic symptoms and the status of gastric emptying.

CONCLUSION

Mitemcinal is capable of accelerating gastric emptying in both diabetic and idiopathic patients with gastroparesis.

Mitemcinal (GM-611), an orally active motilin agonist, facilitates defecation in rabbits and dogs without causing loose stools

The effects of mitemcinal (GM-611), an orally active motilin agonist, on defecation were investigated in rabbits and dogs. In normal rabbits, within 0-3 h of dosing, orally administered mitemcinal (2.5-10 mg kg(-1)) increased stool weight in a dose-dependent manner without causing loose stools. Sennoside (12-48 mg kg(-1)) also facilitated defecation within 2-9 h of oral administration, but the stools were significantly loosened. In the morphine-induced constipation model, the stool weight of morphine-treated rabbits (1 mg kg(-1)) was only 37.5% of that of untreated animals. Mitemcinal (0.5-20 mg kg(-1)) dose-dependently increased stool weight without increasing stool water content. At the highest dose of mitemcinal, stool weight recovered to 83.9% of that of untreated animals. In normal dogs, mitemcinal (0.3-3 mg kg(-1)) reduced the time to first bowel movement after oral administration without inducing diarrhoea at any dose. These results indicate that mitemcinal facilitates defecation without inducing severe diarrhoea. It is suggested that mitemcinal may be a novel therapeutic agent for constipation that enables easier control of the timing of defecation because of the early onset and short duration of its action, compared with sennoside.

Expression of motilin in the hypothalamus and the effect of central erythromycin on gastric motility in diabetic rats

OBJECTIVE

To investigate the expression of motilin-immunoreactive neurons in the hypothalamus and the effect of central administration of erythromycin (EM) on the regulation of gastric motility in diabetic rats.

METHODS

The motilin immunoreactive neurons in the hypothalamus and the hippocampus were detected by immunohistochemistry with rabbit anti-motilin polyclonal antibody. To measure the gastric motility, force transducers were surgically affixed to the gastric serosa. A microinjection syringe was connected via a plastic tube to an injection cannula, which was connected with a stainless steel guide cannula. The syringe was inserted into the right lateral cerebral ventricle for microinjecting the chemicals.

RESULTS

Diabetic mellitus was successfully induced in cohorts of rats. Motilin-immunoreactive neurons significantly increased in the paraventricular (PVN) and supraoptic nuclei (SON) of the hypothalamus in the diabetic rats. Intracerebroventricular (i.c.v.) administration of EM, a motilin receptor agonist, stimulated the gastric motility of diabetic rats. EM (91.56 nmol, i.c.v.) dose-dependently increased the amplitude by (174.82 +/- 48.62)% (P<0.05), and increased the frequency by (70.43 +/- 27.11)% (P < 0.05) in 5 min. The stimulatory effect lasted more than 15 min to the end of the measurement, and can be blocked partially by the prior treatment of motilin receptor antagonist GM-109.

CONCLUSION

Motilin-immunoreactive neurons are increased in the PVN and SON of the hypothalamus in diabetic rats. Centrally administered EM may regulate gastric motility by binding to the central motilin receptors, and central motilin might be involved in regulation of gastric motility in diabetic rats.

Discovery of a Potent and Novel Motilin Agonist

A novel series of dihydro- and tetrahydrotriazolopyridazine-1,3-dione-based amino acid derivatives were identified as very potent motilin receptor agonists. Incorporating one additional phenylethyl glycinamide subunit to 1 (EC(50) = 660 nM) was found to improve in vitro potency approximately 3000-fold, resulting in compound 10 (EC(50) = 0.22 nM). The more potent enantiomer 11A has an EC(50) of 0.047 nM in the motilin receptor functional assay and a K(i) of 0.7 nM in the binding assay. In addition, compound 11A was shown to have a significantly reduced tendency to cause receptor desensitization as compared with the motilin receptor agonist ABT-229.

Effect of low-dose oral erythromycin on gastric aspirates in ventilated neonates less than 32 weeks of gestation. Preliminary results

In this prospective study, the 24-hour gastric aspirate volume was carefully recorded before, 24 and 48 h after administering 1.7 mg/kg/8-hourly of oral erythromycin to 16 ventilated neonates less than 32 weeks of gestation. Their median gestational age was 28.5 weeks (range 23-31 weeks), their median birthweight was 1,045 g (range 690-1,560 g) and the median day of life at which erythromycin was commenced was 9.5 days (range 4-16 days). Prior to administering erythromycin median 24-hour gastric aspirate volume, expressed as a percentage of the milk volume given over the same period, was 38.5% (range 20.0-100%). It was significantly lower 24 h (median 12%, range 0-41%, p = 0.0004) and 48 h (median 5%, range 0-21%, p = 0.0004) after commencing erythromycin. There was also significant reduction of gastric aspirate volume between 24 and 48 h after commencing erythromycin (p = 0.0024). Milk volume increment over the same period was not significant (p = 0.1022). These preliminary results warrant further evaluation through a randomised controlled trial.

Effects of ABT-229, a motilin agonist, on acid reflux, oesophageal motility and gastric emptying in patients with gastro-oesophageal reflux disease

AIM

The effect of ABT-229, a new macrolide with no antibacterial activity, on gastro-oesophageal reflux, oesophageal motility and gastric emptying in patients with gastro-oesophageal reflux disease was investigated.

METHODS

Twenty-one patients were treated with a placebo and ABT-229 (2.5, 5 or 10 mg b.d.) in a randomized, incomplete crossover study design. Ambulatory 24-h pH manometry was performed and gastric emptying was assessed by the 13C-octanoic acid breath test on the seventh day of treatment.

RESULTS

A significant decrease was found in the mean (+/- s.e.) percentage of reflux time (intra-oesophageal pH < 4) for ABT-229 5 mg b.d. and 10 mg b.d., but not for 2.5 mg b.d., compared with placebo. For ABT-229 5 mg, it was 8.5 +/- 0.5% vs. 10.7 +/- 0.7% (P < 0.038) and, for ABT-229 10 mg, it was 6.6 +/- 0.5% vs. 8.4 +/- 0.5% (P < 0.019). There were no significant differences in any of the analysed manometric parameters. In addition, the gastric half-emptying time for all doses of ABT-229 did not differ significantly from that after placebo.

CONCLUSIONS

ABT-229 is able to reduce slightly, but significantly, acid reflux in patients with gastro-oesophageal reflux disease. This effect does not appear to be due to a measurable improvement in oesophageal motility or gastric emptying.

In vitro evaluation of motilin agonism by macrolide immunosuppressive drugs

BACKGROUND

The immunosuppressive drugs tacrolimus and sirolimus may have a stimulatory influence on gastric emptying, in view of their macrolide structure. The aim of this study was to investigate in vitro the possible interaction of tacrolimus and sirolimus with motilin receptors in the rabbit antrum and duodenum.

METHODS

Rabbit duodenum strips were mounted under a load of 1 g in 10 ml organ baths containing Krebs solution. Erythromycin, tacrolimus, cyclosporin, and sirolimus were added to the bathing solution in a cumulative way; in a second series, after incubation with cyclosporin (10(-7) mol/l), tacrolimus (10(-8) mol/l), or sirolimus (3 x 10(-8) mol/l), a cumulative concentration-response curve to erythromycin was obtained. The effect of cumulatively added tacrolimus and nle(13)-porcine motilin on the contractile response to electrical field stimulation was tested in strips from the rabbit gastric antrum. Displacement by tacrolimus of (125)I-nle(13)-porcine motilin bound to its receptor was tested with crude homogenates of the smooth-muscle layer of the rabbit antrum.

RESULTS

In rabbit duodenum strips, carbachol (10(-5) mol/l) induced a stable and reproducible contraction. Erythromycin induced concentration-dependent contractions. Expressed as a percentage of the response to carbachol, the maximal attained effect was 78%; the EC(50) was 4.8 x 10(-7) mol/l. Tacrolimus (10(-8) to 10(-5) mol/l), cyclosporin (10(-8) to 10(-5) mol/l), and sirolimus (10(-8) to 3 x 10(-5) mol/l) had no influence. The response to erythromycin (10(-8) to 3 x 10(-5) mol/l) in the presence of cyclosporin (10(-7) mol/l), tacrolimus (10(-8) mol/l), or sirolimus (3 x 10(-8) mol/l) did not differ from that obtained with erythromycin alone, except for a decrease of the EC(50) in the presence of tacrolimus (2.2 x 10(-7) mol/l) (P<0.05 vs erythromycin alone). Motilin enhanced the response to electrical field stimulation of rabbit antral strips, but tacrolimus had no stimulatory effect. Tacrolimus weakly displaced motilin bound to its receptor. The pIC(50) was 4.97.

CONCLUSIONS

As opposed to erythromycin, neither tacrolimus nor sirolimus showed a contractile effect in the rabbit duodenum. Tacrolimus did not activate the neural motilin receptor of the rabbit gastric antrum and had low affinity for the smooth-muscle motilin receptor. It is thus unlikely that these macrolide immunosuppressive drugs possess gastroprokinetic effects via motilin agonism.

Design and synthesis of novel tetra-peptide motilin agonists

A series of novel tetra-peptide motilin agonists, having the general structure H-Phe-Val-X-Ile-NH(2), were designed, on the basis of structure-activity relationship studies of motilin. Peptides, in which X is a side chain substituted tryptophan residue, have agonistic activity. H-Phe-Val-Trp(2'-CH(2)CH(2)OH)-Ile-NH(2)(7), H-Phe-Val-Trp(2'-SCH(3))-Ile-NH(2)(8), and H-Phe-Val-Trp(2'-SCH(2)CH(2)CH(3))-Ile-NH(2)(9), showed an EC(50) for contractile activity in the rabbit smooth muscle of 14.1+/-3.2, 12.9+/-4.1, and 4.6+/-1.6 microM, respectively. Interaction of the tryptophan aliphatic side chain with motilin receptor appears to influence the signal transduction via motilin receptor.

Motilin and motilin receptors: characterization and functional significance

In order to get more insight into the mechanism of action of the gastrointestinal peptide, motilin, and its role in human physiology, we aimed at characterizing motilin and motilin receptors. Motilin. Sequence analysis of the motilin precursor from several species indicated that the N- and C-terminal regions of the motilin precursor have evolved at different rates. Sequence analysis of the motilin precursor in brain tissue of rabbit and man and motilin radioimmunoassay on tissue extracts, proved that motilin is a brain-gut peptide. Plasma motilin levels are increased in patients with ulcerative colitis or Crohn's disease. A weak correlation between the motilin genotype and the susceptibility to inflammatory bowel disease was demonstrated. Motilin receptors. Motilin receptors are expressed early postnatally and can be regulated by changes in its plasma level. The pharmacophore of motilin consists of the aromatic rings from Phe1 and Tyr7 and the aliphatic side chains from Val2 and Ile4. In vivo and in vitro studies showed that in the rabbit and human antrum, smooth muscle and neuronal motilin receptors exist which have different characteristics. In the rabbit duodenum motilin's action depends upon the influx of extra- and intracellular Ca2+. Nevertheless, in primary smooth muscle cultures, Ca2+ influx through L-type Ca2+ channels is the major transduction mechanism. The existence of central motilin receptors was demonstrated by autoradiography. Receptor binding studies allowed the identification of two binding sites. In contrast to antral smooth muscle cells, the response to motilin in the human TE671 medulloblastoma cell line, expressing the motilin receptor, relies on intracellular IP3-sensitive Ca2+ stores. The antibiotic erythromycin-A (EM-A) binds to the motilin receptor and induces contractions with the same regional and species specificity as motilin. This interaction was supported by the discovery of motilin antagonists. Structure activity studies led to the development of more powerful erythromycin derivatives, which lack antibiotic properties and which are now in clinical trial for treatment of hypomotility disorders. Conclusion and perspectives. The physiological role of motilin and its receptors in the brain requires further investigation. Erythromycin and its derivatives act as motilin agonists with clinically useful prokinetic potential. The motilin receptor has recently been cloned and has substantial structural homology with the growth hormone secretagogue receptor. This may not only lead to the further characterization of motilin receptor subtypes and aid the development of safe and selective motilin receptor agonists and antagonists, useful for the treatment of GI disorders, but may also give a new dimension to the role of motilin in human physiology.

Pressure-geometry relationship in the antroduodenal region in humans

Understanding of the control mechanisms underlying gastric motor function is still limited. The aim of the present study was to evaluate antral pressure-geometry relationships during gastric emptying slowed by intraduodenal nutrient infusion and enhanced by erythromycin. In seven healthy subjects, antral contractile activity was assessed by combined dynamic magnetic resonance imaging and antroduodenal high-resolution manometry. After intragastric administration of a 20% glucose solution (750 ml), gastric motility and emptying were recorded during intraduodenal nutrient infusion alone and, subsequently, combined with intravenous erythromycin. Before erythromycin, contraction waves were antegrade (propagation speed: 2.7 +/- 1.7 mm/s; lumen occlusion: 47 +/- 14%). Eighty-two percent (51/62) of contraction waves were detected manometrically. Fifty-four percent of contractile events (254/473) were associated with a detectable pressure event. Pressure and the degree of lumen occlusion were only weakly correlated (r(2) = 0.02; P = 0.026). After erythromycin, episodes of strong antroduodenal contractions were observed. In conclusion, antral contractions alone do not reliably predict gastric emptying. Erythromycin induces strong antroduodenal contractions not necessarily associated with fast emptying. Finally, manometry reliably detects ~80% of contraction waves, but conclusions from manometry regarding actual contractile activity must be made with care.

Effects of a motilin receptor agonist (ABT-229) on upper gastrointestinal symptoms in type 1 diabetes mellitus: a randomised, double blind, placebo controlled trial

INTRODUCTION

Erythromycin, a motilin agonist, is a potent prokinetic. ABT-229 is a specific motilin agonist that dose dependently accelerates gastric emptying. Dyspepsia and gastroparesis are common problems in type 1 diabetes mellitus. We aimed to evaluate the efficacy of ABT-229 in symptomatic diabetic patients with and without delayed gastric emptying.

METHODS

Patients with type 1 diabetes and postprandial symptoms were randomised (n=270). Based on a validated C(13) octanoic acid breath test, patients were assigned to either the delayed or normal gastric emptying strata. Patients received one of four doses of ABT-229 (1.25, 2.5, 5, or 10 mg twice daily before breakfast and dinner) or placebo for four weeks following a two week baseline. A self report questionnaire measured symptoms on visual analogue scales; the primary outcome was assessment of change in the total upper abdominal symptom severity score (range 0-800 mm) from baseline to the final visit.

RESULTS

The treatment arms were similar regarding baseline characteristics. There was symptom improvement on placebo and a similar level of improvement on active therapy for the upper abdominal discomfort severity score (mean change from baseline -169, -101, -155, -143, and -138 mm for placebo, and 1.25, 2.5, 5, and 10 mg ABT-229, respectively, at four weeks by intent to treat). The results were not significantly different in those with and without delayed gastric emptying. The severity of bloating, postprandial nausea, epigastric discomfort, heartburn, and acid regurgitation worsened dose dependently in a greater number of patients receiving ABT-229 than placebo. Overall, 63% of patients on placebo reported a good or excellent global response, and this was not different from the active treatment arms.

CONCLUSIONS

The motilin agonist ABT-229 was not efficacious in the relief of postprandial symptoms in diabetes mellitus in the presence or absence of delayed gastric emptying.

Demonstration of a functional motilin receptor in TE671 cells from human cerebellum

BACKGROUND

Our laboratory has described the presence of motilin receptors in the rabbit cerebellum. We discovered its presence in the human TE671 cell line, which is of cerebellar origin.

METHODS

Cytosolic Ca(2+) fluxes were monitored on a confocal microscope in cells loaded with Indo-1 and stimulated with motilin under various conditions. Binding studies were performed with 125I-[Nle(13)]porcine motilin. Using primers, PCR for the motilin receptor was performed.

RESULTS

Cells responded to motilin after 45+/-20 s. At different concentrations of motilin (10(-8), 10(-7), 10(-6.5), 10(-6) and 10(-5) M) the percentage of responding cells was 0+/-0, 0.6+/-1.5, 4.9+/-4.7, 21.7+/-15 and 35.7+/-12, respectively. The response was blocked by the motilin antagonists [Phe(3), Nle(13)]po-motilin (0.8+/-1.8%) and GM-109 (0.0+/-0.0%) and mimicked by the agonist ABT-229 (23.6+/-15%). After stimulation with motilin, ABT-229 or [Phe(3),Leu(13)]po-motilin, but not with the antagonist GM-109, cells were desensitized. The response to motilin persisted in Ca(2+)-free solution (22.8+/-14.7%), was not affected by nifedipine (44+/-11%) but was abolished by incubation with thapsigargin (0+/-0%). Neither ryanodine, nor a previous stimulation with caffeine (0+/-0%) in Ca(2+)-free Krebs, nor both could block the response to motilin (28, 32.0+/-5.7, 41.3+/-6.1%, respectively). Binding studies revealed two binding sites for motilin, with a pK(d) of 8.9+/-0.05 and 6.11+/-0.61 (n=4). There were 100 times more low than high affinity receptors per cell. The presence of receptor mRNA was confirmed by PCR.

CONCLUSION

Functional motilin receptors are present in TE671 cells. The response requires intracellular IP(3)-sensitive Ca(2+) stores. These cells may serve as a model of the central motilin receptor.

The effect of motilin agonist ABT-229 on gastro-oesophageal reflux, oesophageal motility and lower oesophageal sphincter characteristics in GERD patients

BACKGROUND

ABT-229, a motilin agonist without antibacterial activity, has been shown to enhance both lower oesophageal sphincter pressure in cats and gastric emptying in humans.

AIM

To investigate the effect of oral treatment with ABT-229 10 mg b.d., ABT-229 5 mg b. d. and cisapride 10 mg q.d.s. on gastro-oesophageal reflux, lower oesophageal sphincter pressure, transient lower oesophageal sphincter relaxations and symptoms in GERD patients.

METHODS

Twenty-four GERD patients completed the study. A randomized, double-blind, placebo-controlled, three-period incomplete crossover design was used with three dosing periods of 7 days. All patients received ABT-229 10 mg b.d. and placebo during two of the three periods. In the remaining period 12 patients were given ABT-229 5 mg b.d. and 12 received cisapride 10 mg q.d.s. Ambulatory 24 h recordings of oesophageal pH and pharyngeal, oesophageal, lower oesophageal sphincter and gastric pressures were performed on day 7 using an assembly incorporating a Dent sleeve connected to a portable water-perfused manometric system.

RESULTS

Oesophageal acid exposure was not affected by ABT-229 or cisapride, but the incidence of reflux episodes was reduced by cisapride. None of the drugs affected oesophageal motility, lower oesophageal sphincter pressure or the incidence of transient lower oesophageal sphincter relaxations. Both ABT-229 10 mg b.d. and cisapride reduced the severity of daytime heartburn.

CONCLUSION

The value of ABT-229 in the treatment of GERD appears to be limited.

Erythromycin, a motilin agonist, increases postprandial gallbladder emptying during therapy with ursodeoxycholic acid

Sufficient gallbladder emptying accelerates early gallstone clearance after extracorporeal shock wave lithotripsy (ESWL). Litholytic therapy with ursodeoxycholic acid (UDC) subsequent to ESWL increases fasting volume (FV) and postprandial residual volume (RV) of the gallbladder. This may lead to retention of cholesterol crystals and small fragments within the gallbladder. In order to find out whether erythromycin, a motilin agonist, improves gallbladder emptying, we tested gallbladder motility after administration of ursodeoxycholic acid with and without oral application of erythromycin. Ten healthy males (age 26-35 years) obtained 10 mg/kg/d of UDCA as a single bedtime dose for three weeks. Prior and after UDCA administration, gallbladder FV was determined sonographically after overnight fasting. After a test meal (490 kcal), gallbladder volume was measured every 5 min until the gallbladder had reached its minimal RV. The next day the same procedure was repeated with 500 mg erythromycin p.o. 45 min prior to test meal application. FV, RV, ejection volume (EV = FV-RV) and ejection fraction (EF = EV/FV x 100) were calculated and differences were compared by the student's t-test. FV (29 ml +/- 8 ml vs. 38 ml +/- 10 ml), RV (12 ml +/- 6 ml vs. 17 ml +/- 6 ml) and EV (17 ml +/- 5 ml vs. 21 ml +/- 6 ml) increased significantly during therapy with UDCA (p < 0.05). EF did not change significantly. After erythromycin application RV decreased to its original values (13 ml +/- 6 ml), whereas EV (24 ml +/- 6 ml) and EF (58% +/- 9% vs. 66% +/- 11%) increased significantly (p < 0.05). Thus, administration of a motilin agonist blunts unwanted effects on gallbladder motility during litholytic therapy with UDC.

Effects of a new motilide, ABT-229, on gastric emptying and postprandial antroduodenal motility in healthy volunteers

BACKGROUND

ABT-229 is a recently developed derivative of erythromycin, devoid of antibiotic activity. We studied the effect of ABT-229 on gastric emptying and postprandial antroduodenal motility in healthy volunteers.

METHODS

Placebo, 4 and 16 mg ABT-229 were given as a single oral dose to nine healthy volunteers, in a randomized, 3-period crossover design. A solid meal (250 kcal) was given twice, 45 min after drug ingestion and 4 h later. Gastric emptying of each meal was studied using the 13C-octanoic breath test. Antroduodenal motility was recorded during the total 9-h period.

RESULTS

After the first meal, both the 4 and 16 mg doses increased the gastric emptying rate to a similar extent. ABT-229 stimulated the contractile motility of the antrum dose-dependently. The half-emptying time and the lag-phase of gastric emptying correlated with the number of pressure waves that were propagated over the antrum and the mean amplitude of antral pressure waves. After the second meal no significant effects of ABT-229 were found.

CONCLUSIONS

A single dose of the new motilin agonist ABT-229 strongly increases the gastric emptying rate in healthy volunteers by increasing the strength and length of propagation of antral pressure waves. ABT-229 has the potential to become a new prokinetic drug.

Motilin and clinical application

Motilin is a regulatory polypeptide of 22 amino acid residues and orginates in motilin cells scattered in the duodenal epithelium of most mammals and chickens. Motilin is released into the general circulation at about 100-min intervals during the interdigestive state and is the most important factor in controlling the interdigestive migrating contractions. Recent studies have revealed that motilin stimulates endogenous release of the endocrine pancreas. Clinical application of motilin as a prokinetic has become possible since erythromycin and its derivatives were proved to be nonpeptide motilin agonists.

Electrophysiological characterization of a motilin agonist, GM611, on rabbit duodenal smooth muscle

Effects of motilin and a newly synthesized erythromycin derivative, GM611, on membrane potential and currents of rabbit duodenal smooth muscle have been investigated by intracellular potential recording and whole cell patch-clamp technique and compared with results from contractile experiments. Motilin and GM611 (0.01-100 nM) dose dependently produced slowly sustained depolarizations (half-maximal effective dose = 0.15 and 3.9 nM for motilin and GM611, respectively) but exhibited biphasic effects on spike activities superimposed on slow waves. With small depolarizations, the number of spike discharges increased, whereas larger depolarizations markedly reduced spike amplitude. Motilin-induced (or GM611-induced) depolarization appeared to be associated with the activation of monovalent cation-selective channels, and the reduction in the spike amplitude appeared mainly to be associated with inhibition of voltage-dependent Ca2+ channels. Furthermore, data from patch-clamp experiments suggested that Ca2+ release occurred from heparin-sensitive internal stores upon stimulation of motilin receptors by these agonists. Possible implications of these electrophysiological effects in motilin- or GM611-induced tonic and phasic contractions have been discussed.

Gallbladder contraction induced by intravenous erythromycin administration. Relation to body mass index

BACKGROUND/AIMS

To study the action of intravenously administered erythromycin lactobionate on human gallbladder volume, as a possible preventive method against gallbladder stone formation, in high risk patients such as those in sepsis, long standing fasting periods or those receiving prolonged total parenteral nutrition or octreotide.

MATERIALS AND METHODS

Twenty-two volunteers randomized to receive intravenously either erythromycin lactobionate 7 mg per kg (study group) or normal saline (controls). We measured ultrasonographically the gallbladder volume before and at 5, 15, 35, 55, 90, 120 and 180 min after the infusion.

RESULTS

Erythromycin induced a biphasic gallbladder contraction, with maximum contractility at 15 min (10.2%) and between 120 and 180 min (22.6%), compared to normal saline controls. Late contractility was correlated to body mass index (BMI).

CONCLUSIONS

Erythromycin activity on gallbladder contraction is proved. Its biphasic action needs further investigation to find the involved mechanism(s). Long term administration is also necessary to test its efficacy in preventing gallbladder dilatation.

[Treatment of radiotherapy-induced gastroparesis with erythromycin]

HISTORY

A 75-year-old woman who had undergone a hysterectomy with adnexectomy followed by radiotherapy for endometrial carcinoma complained of postprandial nausea with vomiting after eating solid foods and of cramp-like abdominal pain, but her appetite was good. She had lost 25 kg in weight over 13 months.

EXAMINATION

Physical examination, laboratory tests, radiology and gastroscopy were unremarkable. Gastric scintigraphy showed abnormally prolonged emptying.

TREATMENT AND COURSE

Nausea and vomiting stopped at once after erythromycin (a motilin agonist) had been administered. It was at first given intravenously after meals (50 mg three times daily for 5 days), then orally for 10 weeks (250 mg three times daily before meals). Subsequent examination revealed normal gastric emptying. The symptoms did not recur after erythromycin had been discontinued.

CONCLUSION

Erythromycin is an effective drug against gastroparesis caused by radiotherapy, because it acts even when the enteric nerves are damaged.

Erythromycin stimulates gastric emptying after esophagectomy with gastric replacement: a randomized clinical trial

Delayed gastric emptying after esophagogastrectomy can pose a significant early postoperative problem. Because erythromycin, which stimulates the gastric antral and duodenal motilin receptor, has been shown to significantly increase gastric emptying in patients with diabetic gastroparesis, we decided to evaluate its effect on gastric emptying after esophagogastrectomy.

METHODS

Twenty-four patients (18 men and six women, age range 41 to 79 years, median 66 years) were randomized to receive either erythromycin lactobionate (200 mg in 50 ml normal saline solution intravenously) (n = 13) or placebo (50 ml normal saline solution intravenously (n = 11) 11 days after esophagogastrectomy (with pyloric drainage procedure). After erythromycin or placebo had been infused over a 15-minute period, patients ingested a solid meal (scrambled egg with bread) labeled with technetium 99m sulfur colloid (500 microCi) over approximately 15 minutes. Dynamic images of the stomach were then acquired over 90 minutes in the supine position by gamma imaging. Results were expressed as percentage of counts retained in the stomach (percent gastric retention) over time.

RESULTS

There were no side effects of erythromycin. In the placebo group, the mean percent of radiolabeled meal retained in the stomach after 90 minutes was 88%, which was significantly greater than in the erythromycin group, 37% (p < 0.001). In addition, analysis of covariance demonstrated that the rate of gastric emptying (slope of the line) was significantly greater in the erythromycin-treated group than in the placebo group (p < 0.0001).

CONCLUSION

Early satiety after esophagogastrectomy may be due to delayed gastric emptying and not due to a decrease in the gastric reservoir. Intravenous erythromycin significantly improves gastric emptying in patients after esophagogastrectomy by stimulating gastric motility.

EM523L, a nonpeptide motilin agonist, stimulates gastric emptying and pancreatic polypeptide secretion

We investigated the efficacy and the mechanism of action of EM523L, a nonpeptide motilin agonist (motilide), on the stimulation of gastric emptying and on the release of gut peptides after ingestion of a solid meat in normal controls (n = 8) and in diabetic patients (n = 8) with signs of neuropathy. A dose of 2 mg EM523L was administered IV over 15 min just after ingestion of a solid meal (200 kcal Gastric emptying was measured by a radionuclide technique. EM523L accelerated gastric emptying and markedly augmented postprandial pancreatic polypeptide (PP) response in both normal control and diabetic patients. This may suggest the mediation of the Vagal-cholinergic pathway to accelerate gastric emptying. The present study offers a promising therapeutic potential of the motilide in gastrointestinal motility disorders like those observed in diabetics mellitus.

Effect of nonpeptide motilin agonist EM523 on release of gut and pancreatic hormones in conscious dogs

BACKGROUND & AIMS

EM523, a nonpeptide motilin agonist, is being developed for clinical use to improve delayed gastric emptying. The aim of this study was to examine the effect of EM523 on endogenous release of gut and pancreatic hormones in conscious dogs.

METHODS

Motility of the gastrointestinal tract was monitored using force transducers. Blood concentrations of gut and pancreatic hormones were measured using a specific radioimmunoassay. EM523 (3 micrograms/kg) or normal saline (5 mL) was given during the phase I period of the interdigestive state.

RESULTS

A single injection of EM523 always induced phase III-like contractions in the intact gastric antrum and was accompanied by significant (P < 0.01) release of motilin, pancreatic polypeptide, and insulin; glucagon, gastrin, cholecystokinin, and secretin were not released by EM523. The significant release of these hormones was suppressed by pretreatment with atropine and completely eliminated by a 5-hydroxytryptamine 3 receptor antagonist and truncal vagotomy.

CONCLUSIONS

The findings suggest that EM523 stimulates the release of pancreatic polypeptide, insulin, and motilin by activating the cholinergic parasympathetic nerve system, finally stimulating the endocrine pancreas through vagally cholinergic muscarinic receptors in the pancreatic islets. The participation of 5-hydroxytryptamine 3 receptors in this system is strongly suggested by the results.

Transduction mechanism of motilin and motilides in rabbit duodenal smooth muscle

The present study was undertaken to explore motilin's transduction pathway in the rabbit. Guanine nucleotides inhibited 125I-motilin binding in rabbit antral tissue and increased the dissociation of motilin from its receptor. Motilin, the motilin agonist erythromycin A enol ether (EM-201) and carbachol (taken as control) increased the production of inositol phosphates in rabbit duodenal smooth muscle strips labeled with myo-[2-3H]inositol. The effect of carbachol was blocked by atropine. Dose-response curves revealed that 50% of this effect was obtained with 3.9 nM motilin, 170 nM EM-201, 0.54 microM carbachol. Chromatographic separation of the inositol phosphate metabolites showed significant increases in the levels of [3H]inositol bisphosphate and of [3H]inositol trisphosphate. The three substances were without effect upon the metabolism of cAMP, nor did they modulate the rise in cAMP induced by GTP. We propose that motilin's transduction pathway uses a G protein that causes an increase in inositol trisphosphate which is rapidly metabolized, and which may release calcium from intracellular stores.

Motilin receptor: a model for development of prokinetics

Erythromycin and related macrolides act as smooth muscle and neural receptors to contract rabbit duodenum and induce phase III migrating motor complex (MMC) activity in intact dogs. A recently developed motilin antagonist confirms that motility effects of erythromycin are mediated by motilin receptors. Despite species, organ, and tissue heterogeneity of motilin receptors, binding experiments with rodent antral smooth muscle tissue provide a good model for the development of this new class of prokinetics.

Pharmacotherapy of gastrointestinal motor disorders

Pharmacotherapy of gastrointestinal motor disorders is complicated by the large variety of drug targets and their interactions, the complex relation between contractile patterns and propulsion and the occurrence of regional and species differences. A number of drug classes are discussed: cholinergic agonists/antagonists, dopamine-antagonists, calcium-entry blockers and spasmolytics, serotonin-5-HT4-agonists, cholecystokinin-antagonists, motilin-agonists, 5-HT3-antagonists, opiate agonists, and laxatives. The number of drug classes is increasing rapidly allowing a more specific treatment for the large number of gastrointestinal disorders related to disturbed motility. An interesting new development is the search for compounds interfering with transmitters of the non-adrenergic non-cholinergic nerves of the enteric nervous system a.o. nitric oxide (NO).