Pathophysiology in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a distressing condition that impairs quality of life, and it deserves to be treated. It also has a large economic impact on healthcare utilization and absenteeism. IBS is a disorder in which three major mechanisms interact: altered gastrointestinal motility, increased sensory function of the intestine and psychosocial factors. The role of prior infection in the development of IBS is the subject of ongoing study. This article focuses on pathophysiological mechanisms, including the potential roles of mucosal changes and neurobiology in the development of IBS. Novel pharmacological agents are being developed to target neural mediators of IBS; they appear promising, and their role in clinical practice will be clarified with regulatory approval and clinical use.

Type I diabetes mellitus does not alter initial splanchnic glucose extraction or hepatic UDP-glucose flux during enteral glucose administration

AIMS/HYPOTHESIS

Our aim was to determine whether an alteration in splanchnic glucose metabolism could contribute to postprandial hyperglycaemia in people with Type I (insulin-dependent) diabetes mellitus.

METHODS

Splanchnic glucose extraction, hepatic glycogen synthesis and endogenous glucose production were compared in 8 Type I diabetic patients and in 11 control subjects. Endogenous hormone secretion was inhibited with somatostatin while insulin (approximately 550 pmol/l) and glucagon (approximately 130 ng/l) concentrations were matched with exogenous hormone infusions. Glucose containing [3-3H] glucose was infused into the duodenum at a rate of 20 micromol.kg(-1).min(-1). Plasma glucose concentrations were maintained at about 8.5 mmol/l in both groups by means of a separate variable intravenous glucose infusion.

RESULTS

Initial splanchnic glucose uptake, calculated by subtracting the systemic rate of appearance of [3-3H] glucose from the rate of infusion of [3-3H] glucose into the duodenum, did not differ in the diabetic and non-diabetic patients (4.1 +/- 0.8 vs 3.0 +/- 1.0 micromol/kg/min). In addition, hepatic glycogen synthesis, measured using the acetaminophen glucuronide method did not differ (10.7 +/- 2.4 vs 10.1 +/- 2.7 micromol.kg(-1).min(-1)). On the other hand, suppression of endogenous glucose production, measured by an intravenous infusion of [6,6-2H2] glucose, was greater (p < 0.05) in the diabetic than in the non-diabetic subjects (1.7 +/- 1.6 vs 5.8 +/- 1.9 micromol.kg(-1).min(-1)).

CONCLUSION/INTERPRETATION

When glucose, insulin and glucagon concentrations are matched in individuals with relatively good chronic glycaemic control, Type I diabetes does not alter initial splanchnic glucose uptake of enterally delivered glucose or hepatic glycogen synthesis. Alterations in splanchnic glucose metabolism are not likely to contribute to postprandial hyperglycaemia in people with well controlled Type I diabetes.

Functional abdominal pain in the elderly

Although aging per se affects function throughout the gut, particularly after age 70, the observed changes are relatively modest and often asymptomatic, perhaps because of the vast reserve of neuromuscular functional elements in the gut. The proximal esophagus, anus, and pelvic floor are possible exceptions to this generalization, and the combination of aging and factors such as minor strokes or obstetric damage often results in dysphagia, constipation, or fecal incontinence. Managing elderly patients with functional abdominal pain demands clinical acumen, tact, understanding, and patience. Further studies are required to elucidate the consequences of aging on gastrointestinal sensorimotor function at several levels of the digestive tract. With the expected explosion in the proportion of the population older than age 75, this field should become a high priority for clinical and research efforts. Also required will be a major campaign to educate patients and practitioners and multidisciplinary collaborations among primary care practitioners, gastroenterologists, psychologists, and physiatrists to provide optimal pain management in the elderly.

Colonic motility in chronic ulcerative proctosigmoiditis and the effects of nicotine on colonic motility in patients and healthy subjects

BACKGROUND

Nicotine decreases diarrhoea and pain in ulcerative colitis without reducing inflammation.

AIMS

(i) To evaluate the effect of ulcerative proctosigmoiditis on motor functions of an uninflamed segment of descending colon; and (ii) to assess nicotine's effects on colonic motor functions in patients and healthy subjects.

METHODS

In healthy subjects (n=30) and patients with ulcerative colitis (13; 11 active, two quiescent colitis), we studied the effects of intravenous nicotine on colonic transit of solid residue by scintigraphy (healthy subjects) and on colonic motility in healthy subjects and 11 patients.

RESULTS

In ulcerative colitis, fasting colonic motility was increased, whereas motor response to a meal was significantly reduced; compliance was unchanged. In healthy subjects, high-dose nicotine induced transient high amplitude propagated contractions and relaxation of the descending colon followed by decreased phasic contractions. This dose also accelerated colonic transit. Low-dose nicotine (mimicking a transdermal nicotine patch) reduced colonic compliance in healthy subjects, but did not affect motor function in ulcerative colitis.

CONCLUSIONS

Ulcerative proctosigmoiditis increases fasting colonic motility and reduces tone response to a meal in the descending colon without affecting colonic compliance, suggesting changes in physiological responses but not intrinsic wall properties. Nicotine has dose-dependent effects on colonic motor activity in healthy subjects.

An open trial of octreotide long-acting release in the management of short bowel syndrome

OBJECTIVES

The aim of this study was to assess the effects of the long-acting release (LAR) depot octreotide preparation Sandostatin LAR Depot on stool water and electrolyte losses, fecal fat excretion, and GI transit in patients with short bowel syndrome.

METHODS

We performed a 15-wk, prospective, open-label study of intramuscular (i.m.) Sandostatin LAR Depot, 20 mg, at 0, 3, 7, and 11 wk. Balance studies were performed before and at the end of the 15-wk study. Baseline and posttreatment measurements of body weight, stool fat, sodium and potassium, and gastric and small bowel transit of a radiolabeled egg meal were compared by paired analysis.

RESULTS

We studied eight patients with short bowel syndrome (five women and three men; mean age 52 yr, range 37-72 yr) who had been TPN dependent for a mean of 11.8 yr (range 1.5-22 yr). The underlying diagnoses were Crohn's disease (n = 6), intestinal ischemia (n = 1), and resection for carcinoid tumor (n = 1). Treatment with Sandostatin LAR Depot significantly increased small bowel transit time (p = 0.03). Changes in body weight, urine volume, stool weight, fecal fat excretion, stool sodium and potassium excretion, or gastric emptying rate were highly variable, and no overall significance was observed.

CONCLUSIONS

Sandostatin LAR Depot for 15 wk significantly prolonged small bowel transit time. Body weight and stool parameters in response to Sandostatin LAR Depot treatment needs to be assessed further in multicenter studies assessing dose, frequency of administration, and a larger sample size.

Effect of glucagon-like peptide-1(7-36)-amide on initial splanchnic glucose uptake and insulin action in humans with type 1 diabetes

In vitro studies indicate that glucagon-like peptide-1(7-36)-amide (GLP-1) can enhance hepatic glucose uptake. To determine whether GLP-1 increases splanchnic glucose uptake in humans, we studied seven subjects with type 1 diabetes on two occasions. On both occasions, glucose was maintained at approximately 5.5 mmo/l during the night using a variable insulin infusion. On the morning of the study, a somatostatin, glucagon, and growth hormone infusion was started to maintain basal hormone levels. Glucose (containing [3H]glucose) was infused via an intraduodenal tube at a rate of 20 micromol.kg(-1).min(-1). Insulin concentrations were increased to approximately 500 pmol/l while glucose was clamped at approximately 8.8 mmol/l for the next 4 h by means of a variable intravenous glucose infusion labeled with [6,6-2H2]glucose. Surprisingly, the systemic appearance of intraduodenally infused glucose was higher (P = 0.01) during GLP-1 infusion than saline infusion, indicating a lower (P < 0.05) rate of initial splanchnic glucose uptake (1.4 +/- 1.5 vs. 4.8 +/- 0.8 micromol.kg(-1).min(-1)). On the other hand, flux through the hepatic uridine-diphosphate- glucose pool did not differ between study days (14.2 +/- 5.5 vs. 13.0 +/- 4.2 micromol.kg(-1).min(-1)), implying equivalent rates of glycogen synthesis. GLP-1 also impaired (P < 0.05) insulin-induced suppression of endogenous glucose production (6.9 +/- 2.9 vs. 1.3 +/- 1.4 micromol.kg(-1).min(-1)), but caused a time-dependent increase (P < 0.01) in glucose disappearance (93.7 +/- 10.0 vs. 69.3 +/- 6.3 micromol.kg(-1).min(-1); P < 0.01) that was evident only during the final hour of study. We conclude that in the presence of hyperglycemia, hyperinsulinemia, and enterally delivered glucose, GLP-1 increases total body but not splanchnic glucose uptake in humans with type 1 diabetes.

Review article: tegaserod

Tegaserod (Zelmac), an aminoguanidine indole derivative of serotonin, is a selective partial agonist highly selective for 5-HT(4) receptor with an affinity constant in the nanomolar range. Tegaserod does not cause adverse pharmacodynamic effects, is absorbed rapidly after oral administration and distributes widely into tissues. Pharmacokinetics of oral tegaserod are linear in the 2--12 mg dose range. After oral administration tegaserod is metabolized mainly pre-systemically; when absorbed, intact tegaserod is excreted as N-glucuronides mainly via the bile. No clinically relevant drug--drug interactions were identified. Tegaserod has proven safe in toxicity studies. In pharmacodynamic studies, tegaserod stimulated the peristaltic reflex in vitro, increased canine intestinal and colonic motility and transit, reduced visceral afferent firing or sensation in response to distension in animals, and accelerated gastric, small bowel and colonic transit in healthy patients, and small bowel transit in patients with constipation-predominant irritable bowel syndrome. Three large phase III randomized, double-blinded, and placebo-controlled trials were performed predominantly in females (approximately 85%) with constipation-predominant irritable bowel syndrome. Overall, phase III results support efficacy as assessed by the subject's global assessment of relief with significant improvement in secondary endpoints such as abdominal pain, bowel frequency and consistency. Tegaserod was well-tolerated; the most frequent adverse event was transient diarrhoea.

Prucalopride accelerates gastrointestinal and colonic transit in patients with constipation without a rectal evacuation disorder

BACKGROUND & AIMS

Prucalopride (PRU) is a selective benzofuran 5-hydroxytryptamine(4)-receptor agonist with gastrointestinal and colonic prokinetic activities. We evaluated the effects of PRU on gastrointestinal and colonic transit in patients with constipation.

METHODS

Gastrointestinal and colonic transit were measured over 48 hours in 40 patients who fulfilled modified Rome I criteria for functional constipation. Patients had no evidence of a rectal evacuation disorder. Subjects were randomized to receive a daily dose of 2 or 4 mg PRU or placebo in a double-blind, parallel-group design. Each treatment lasted 7 days. The transit test was performed over the last 48 hours of the study. Effects on gastric emptying, small bowel transit, and colonic transit were analyzed using Kruskal-Wallis and Wilcoxon rank sum tests.

RESULTS

Of 61 patients screened, 40 were eligible and randomized. Two patients withdrew because of adverse events. PRU accelerated overall gastric emptying and small bowel transit. PRU tended to accelerate overall colonic transit with significantly faster overall colonic transit and ascending colon emptying with the 4-mg dose.

CONCLUSIONS

PRU accelerates transit through the stomach, small bowel, and colon in patients with constipation unassociated with a rectal evacuation disorder.

Management of the irritable bowel syndrome

Irritable bowel syndrome (IBS) is the most common disorder diagnosed by gastroenterologists and one of the more common ones encountered in general practice. The overall prevalence rate is similar (approximately 10%) in most industrialized countries; the illness has a large economic impact on health care use and indirect costs, chiefly through absenteeism. IBS is a biopsychosocial disorder in which 3 major mechanisms interact: psychosocial factors, altered motility, and/or heightened sensory function of the intestine. Subtle inflammatory changes suggest a role for inflammation, especially after infectious enteritis, but this has not yet resulted in changes in the approach to patient treatment. Treatment of patients is based on positive diagnosis of the symptom complex, limited exclusion of underlying organic disease, and institution of a therapeutic trial. If patient symptoms are intractable, further investigations are needed to exclude specific motility or other disorders. Symptoms fluctuate over time; treatment is often restricted to times when patients experience symptoms. Symptomatic treatment includes supplementing fiber to achieve a total intake of up to 30 g in those with constipation, those taking loperamide or other opioids for diarrhea, and those taking low-dose antidepressants or infrequently using antispasmodics for pain. Older conventional therapies do not address pain in IBS. Behavioral psychotherapy and hypnotherapy are also being evaluated. Novel approaches include alosetron; a 5-HT(3) antagonist, tegaserod, a partial 5-HT(4) agonist, kappa-opioid agonists, and neurokinin antagonists to address the remaining challenging symptoms of pain, constipation, and bloating. Understanding the brain-gut axis is key to the eventual development of effective therapies for IBS.

Paraneoplastic gastrointestinal motor dysfunction: clinical and laboratory characteristics

OBJECTIVES

The aim of this study was to describe the clinical, manometric, and serological characteristics of 12 patients with paraneoplastic GI motor dysfunction and to assess the contributory role of diagnostic tests.

METHODS

Twelve patients diagnosed with malignant tumors and GI motor dysfunction were identified at the Mayo Clinic from 1985 to 1996.

RESULTS

Cancers identified were: nine small cell lung carcinoma (SCLC), one anaplastic lung adenocarcinoma, one retroperitoneal lymphoma, and one ovarian papillary serous adenocarcinoma. GI symptoms preceded the tumor diagnosis in all cases of SCLC (mean, -8.7 months, range, -1 to -24 months, n = 9). The diagnosis of a malignant tumor preceded the onset of GI symptoms in the three patients with other neoplasms (6, 12, and 24 months). Five of the nine patients found to have SCLC had no evidence of tumor on initial chest x-ray. One or more paraneoplastic autoantibodies were found in 10 of the 11 patients tested by autoimmune serology. Type 1 antineuronal nuclear antibody (ANNA-1 or anti-Hu) was detected in eight of the nine patients with SCLC (one patient was not tested). The patient with ovarian carcinoma had type 1 Purkinje cell cytoplasmic antibody (PCA-1 or anti-Yo). N-type calcium channel antibodies were found in one patient with SCLC, one with a retroperitoneal B cell lymphoma, and one with ovarian carcinoma. Gastric emptying was delayed in 89% (eight of nine tested) and 80% (four of five tested) had esophageal dysmotility. Autonomic reflex tests were abnormal in the seven patients tested.

CONCLUSIONS

The diagnosis of paraneoplastic GI motor dysfunction requires a high index of clinical suspicion. A panel of serological tests for paraneoplastic autoantibodies, scintigraphic gastric emptying, and esophageal manometry are useful as first-line screening tests. Seropositivity for ANNA-1, PCA-1, or N-type calcium channel-binding antibodies should prompt further evaluation for an underlying malignancy even when routine imaging studies are negative.

Novel testing of human gastric motor and sensory functions: rationale, methods, and potential applications in clinical practice

Sensitive and reproducible tests are essential to investigate the mechanisms of gastric motility and sensation in healthy humans and patients with unexplained upper gastrointestinal symptoms. Electrogastrography, manometry, scintigraphic emptying, and barostat studies with an intragastric balloon were initially used to understand physiology and pathophysiology of gastric motility. However, manometry and barostat studies are time-consuming, costly, and invasive, thus reducing their widespread clinical application. To overcome these shortcomings, several novel approaches have been proposed: water/nutrient drink test, paracetamol absorption test, 13C-octanoic acid or spirulina breath tests, ultrasonography, magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and tensostat. The water/nutrient (satiety) test is a noninvasive test proposed as an alternative to sensory studies performed with an intragastric balloon. The satiety test cannot measure gastric accommodation; interpretation of sensory tests usually has required independent assessment of accommodation or compliance. The tensostat can be used as a gastric sensation test because it measures gastric wall tension, which is related to the perception of gastric distention. To measure gastric emptying, the paracetamol absorption test, 13C breath tests, ultrasound, or MRI can be used. The paracetamol absorption test can measure the gastric emptying of liquids. 13C breath test can measure the gastric emptying of solids or liquids and can achieve accuracy comparable with gastric scintigraphy. Ultrasonography requires special skills, and MRI requires costly equipment. To measure gastric accommodation to a meal, ultrasound, MRI, and SPECT have been proposed. The recently introduced SPECT requires an intravenous injection of 99mTc-pertechnetate, which the gastric mucosa specifically takes up, and specialized imaging and analysis, which have potential to be automated. Thus, novel, noninvasive approaches assess different dimensions of gastric motility and sensation testing. With further development of these techniques, refinement of their conduct and analysis, and validation of clinical usefulness, they are likely to be applicable in clinical practice to enhance cost-effective, evidence-based management of upper gastrointestinal symptoms. Such applications may provide an alternative to sequential empirical trials for symptoms.

Functional bowel disease: roles of sensation and motility

Functional bowel disorders are collections of symptoms attributable to the mid or lower gastrointestinal tract. The two most common disorders, irritable bowel syndrome and functional dyspepsia, have common etiopathogenetic features, notably psychosocial disturbances, dysmotility and heightened sensitivity. The control mechanisms, pathophysiology, investigation and potential pharmacotherapies of these disorders are reviewed. Serotonergic and adrenergic agents are among the novel approaches that may have a significant impact on these disorders.

Effects of a serotonin 5-HT(4) receptor antagonist SB-207266 on gastrointestinal motor and sensory function in humans

BACKGROUND

Serotonin 5-HT(4) receptors are located on enteric cholinergic neurones and may regulate peristalsis. 5-HT(4) receptors on primary afferent neurones have been postulated to modulate visceral sensation. While 5-HT(4) agonists are used as prokinetic agents, the physiological role of 5-HT(4) receptors in the human gut is unknown.

AIMS

Our aim was to characterise the role of 5-HT(4) receptors in regulating gastrointestinal motor and sensory function in healthy subjects under baseline and stimulated conditions with a 5-HT(4) receptor antagonist.

METHODS

Part A compared the effects of placebo to four doses of a 5-HT(4) receptor antagonist (SB-207266) on the cisapride mediated increase in plasma aldosterone (a 5-HT(4) mediated response) and orocaecal transit in 18 subjects. In part B, 52 healthy subjects received placebo, or 0.05, 0.5, or 5 mg of SB-207266 for 10-12 days; gastric, small bowel, and colonic transit were measured by scintigraphy on days 7-9, and fasting and postprandial colonic motor function, compliance, and sensation during distensions were assessed on day 12.

RESULTS

Part A: 0.5, 5, and 20 mg doses of SB-207266 had significant and quantitatively similar effects, antagonising the cisapride mediated increase in plasma aldosterone and acceleration of orocaecal transit. Part B: SB-207266 tended to delay colonic transit (geometric centre of isotope at 24 (p=0.06) and 48 hours (p=0.08)), but did not have dose related effects on transit, fasting or postprandial colonic motor activity, compliance, or sensation.

CONCLUSION

5-HT(4) receptors are involved in the regulation of cisapride stimulated orocaecal transit; SB 207266 tends to modulate colonic transit but not sensory functions or compliance in healthy human subjects.

Gastrointestinal tract symptoms among persons with diabetes mellitus in the community

BACKGROUND

Gastrointestinal (GI) tract symptoms are common among patients with diabetes mellitus (DM) seen in tertiary care centers. The degree to which this reflects referral bias is unclear.

OBJECTIVES

To determine whether GI tract symptoms are more prevalent in unselected patients with DM from the general community compared with their age- and sex-matched counterparts without DM and to assess the association of GI tract symptoms in persons with DM with psychosomatic symptoms, medication use, and symptoms of autonomic neuropathy.

METHODS

In this population-based, cross-sectional study, Olmsted County, Minnesota, residents with type 1 DM, a random sample of residents with type 2 DM, and 2 age- and sex-stratified random samples of nondiabetic residents (total of 1262 person for the 4 groups) were mailed a previously validated symptom questionnaire.

RESULTS

Heartburn was less common in residents with type 1 DM vs controls (12% vs 23%; P<.05). No significant difference in prevalence was detected (residents with type 1 DM vs controls; residents with type 2 DM vs controls) for nausea or vomiting (12% vs 11%; 6% vs 6%), dyspepsia (19% vs 21%; 13% vs 17%), or constipation (17% vs 14%; 10% vs 12%). However, constipation and/or laxative use was slightly more common in residents with type 1 DM (27% vs 19%; P<.15), particularly in men, and was associated with the intake of calcium channel blockers.

CONCLUSIONS

In the community, the prevalence of most GI tract symptoms is similar in persons with or without DM, except for a lower prevalence of heartburn and an increased prevalence of constipation or laxative use in residents with type 1 DM, especially in men. This difference is associated with calcium channel blocker use rather than symptoms of autonomic neuropathy. In community-based practices, physicians should not immediately assume that GI tract symptoms in patients with DM represent a complication of DM.

Toward office-based measurement of gastric emptying in symptomatic diabetics using [13C]octanoic acid breath test

OBJECTIVE

Current methods for measuring gastric emptying by breath test require sampling over several hours and are too inaccurate for clinical use. The aim of this study was to develop an office-based method for measuring gastric emptying of solids in patients with diabetes using a [13C]octanoic acid breath test.

METHODS

In 22 symptomatic diabetic patients (17 insulin-dependent diabetes, 5 non-insulin-dependent diabetes) and 6 controls, we simultaneously measured gastric emptying of an egg meal (420 kcal) by scintigraphy and [13C]octanoic acid breath test. Conventional (nonlinear) methods for scintigraphic and [13C]octanoic acid breath test emptying and generalized linear regression method to predict scintigraphic half-life (t(1/2)) using four breath samples obtained during the first 3 h.

RESULTS

Despite 8 h of breath sampling, the t(1/2) estimate using the conventional method was markedly different from the scintigraphic value (delta t(1/2): median, 113 min; range, 19-282 min). The generalized linear model (using samples at baseline, 30, and 120 or 150 min) yielded predicted scintigraphic tLAG and t(1/2) that were more accurate than the conventional method; mean standard deviations of differences were 16 and 27 min, respectively. Breath test correctly assessed normal or prolonged emptying in 21 of 22 patients.

CONCLUSIONS

The [13C]octanoic acid breath test can be simplified to measure gastric tLAG and t(1/2) and can be expected to correctly identify normal t(1/2) in symptomatic diabetics. Further refinement of the model will need to include studies of patients with markedly delayed t(1/2).

New therapies for functional bowel diseases

During recent years, a greater understanding of the pathophysiology of functional bowel disease, and a surge of interest in this challenge among pharmacologists, basic scientists, and clinical investigators, have led to novel insights and promising therapies. The evidence to support current therapies in nonculcer dyspepsia and irritable bowel syndrome (IBS) is reviewed, and some of the novel therapeutic approaches on the threshold of clinical application are described.

Insights into the pathophysiology and mechanisms of constipation, irritable bowel syndrome, and diverticulosis in older people

OBJECTIVES

To review the epidemiology, pathophysiology and mechanisms of irritable bowel syndrome (IBS), constipation, and diverticulosis, for the purpose of addressing these three common conditions in older adults (>65 years of age).

DESIGN

Using a MEDLINE search, we identified original English language journal articles and reviews from 1965 to December 1998. We also selected articles published before 1965 or after 1998 that were cross-referenced or pertinent to the topics researched.

RESULTS

The prevalence of constipation and diverticulosis is higher in older than in younger adults. Significant risk factors for constipation in older women are failure of the anorectal angle to open or excessive perineal descent, which represent disturbances of pelvic floor function and rectal evacuation. In contrast, the prevalence of IBS is no greater than in younger adults. Nevertheless, these syndromes impact on the patient's functional status and quality of life. The mechanisms resulting in these gastrointestinal syndromes are unclear. Uncoordinated colonic activity and colonic segmentation may lead to IBS and diverticulosis, respectively, and these pathophysiological findings suggest disorders of inhibitory control of neuromuscular function. The total number of neurons in the myenteric plexus is decreased, and collagen deposited in the distal colon is increased with aging in humans. Animal studies suggest that senescent colonic muscle responds less to excitatory factors in vitro, and neural injury in older animals may result from apoptosis, defects of mitochondrial metabolism, and inadequate levels or response to neurotrophins. Future investigations will reveal whether similar mechanisms underlie human disease. Currently, treatment is aimed at relief of symptoms of IBS or constipation or dealing with the complications of diverticulosis.

CONCLUSIONS

Constipation, IBS, and diverticulosis are common problems of aging. There is a need for further systematic research of the basic mechanisms in neuromuscular dysfunction with aging, including the studies of physical characteristics of the colonic wall, pelvic floor function (particularly in women with excessive perineal descent), and neurohormonal control of motility and sensation. Insights on the pathophysiology and mechanisms of neural injury may lead to more specific treatments in the future, e.g., serotonergic agents and neurotrophins. Meanwhile, collaborations between primary care physicians, geriatricians, and gastroenterologists can optimize management of these three common conditions that significantly impact the quality of life of older adults.

Effects of alosetron on gastrointestinal transit time and rectal sensation in patients with irritable bowel syndrome

BACKGROUND

Alosetron, a 5-HT3-receptor antagonist, relieves abdominal pain and improves bowel function in non-constipated, female patients with irritable bowel syndrome. 5-HT3 antagonists delay colonic transit, increase colonic compliance, and increase small intestinal water absorption.

AIM

To evaluate the effects of alosetron on gastrointestinal and colonic transit, rectal compliance and rectal sensation in irritable bowel syndrome.

METHODS

A double-blind, placebo-controlled, two-dose study of alosetron was performed in 25 non-constipated irritable bowel syndrome patients, with paired studies before and after 4 weeks of treatment with placebo (n=5), 1 mg alosetron (n=10) or 4 mg (n=10) alosetron b.d. Gastrointestinal and colonic transit were measured by scintigraphy. Rectal compliance and sensation were assessed by rectal balloon distention with a barostat.

RESULTS

There was a trend (P=0.06) for 1 mg alosetron to increase rectal compliance (median pressure at half maximum volume 11 mmHg after alosetron vs. 15.6 mmHg before alosetron). The 1 mg b.d. alosetron dose non-significantly retarded proximal colonic transit. Alosetron and placebo reduced sensory scores relative to baseline values; none of the changes induced by alosetron was significant relative to placebo.

CONCLUSIONS

Alosetron had no significant effect on gastrointestinal transit or rectal sensory and motor mechanisms in non-constipated irritable bowel syndrome patients in this study. Alosetron's effects on colonic sensorimotor function and central sensory mechanisms deserve further evaluation.