Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P46098 (5-HT3 receptor)
 2,290 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dolasetron (dolasetron mesilate) is a pseudopelletierine-derived 5-HT3 antagonist which has recently become available for clinical use. It is rapidly converted in vivo to its active major metabolite, hydrodolasetron, which appears to be largely responsible for its pharmacological activity. In clinical trials, single intravenous or oral doses of dolasetron were effective in preventing acute chemotherapy-induced nausea and vomiting (CINV). Intravenous doses of 1.8 mg/kg achieved complete suppression of vomiting in approximately 50% of patients receiving highly emetogenic cisplatin-containing chemotherapy and in approximately 60 to 80% of patients receiving moderately emetogenic chemotherapy. In the latter setting, oral doses of 200 mg achieved similar response rates. In comparative studies, intravenous dolasetron 1.8 mg/kg was as effective as intravenous granisetron 3 mg or ondansetron 32 mg after highly emetogenic chemotherapy, and oral dolasetron 200 mg was equivalent to multiple oral doses of ondansetron (3 or 4 doses of 8 mg) after moderately emetogenic chemotherapy. Dolasetron 1.8 mg/kg was superior to metoclopramide in preventing emesis induced by high dose cisplatin or by moderately emetogenic chemotherapy in high risk subgroups. Dolasetron has also shown efficacy in preventing radiotherapy-induced nausea and vomiting (RINV) in preliminary studies. Single intravenous or oral dolasetron doses ranging from 12.5 to 100 mg and 25 to 200 mg, respectively, were significantly more effective than placebo in preventing postoperative nausea and vomiting (PONV) in female surgical patients. A 50 mg intravenous dose was as effective in preventing PONV as ondansetron 4 mg in a mixed-gender group. Intravenously administered dolasetron was also effective in treating established PONV, although complete suppression of vomiting was achieved in < 40% of patients. Dolasetron has a tolerability profile characteristic of this class of compounds, with headache, dizziness and diarrhoea being the most commonly occurring adverse events in clinical trials. Diarrhoea is not thought to be related to dolasetron administration, being experienced mostly by patients receiving chemotherapy. Dolasetron and other 5-HT3 receptor antagonists have been associated with minor changes in ECG intervals, but these generally do not appear to be clinically important. Thus, available evidence suggests that dolasetron will provide an alternative to other 5-HT3 receptor antagonists for the management of CINV and PONV. Further studies are required to determine whether it offers any advantages over other agents in these settings and to determine the optimum dosage for preventing RINV.
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PMID:Dolasetron. A review of its pharmacology and therapeutic potential in the management of nausea and vomiting induced by chemotherapy, radiotherapy or surgery. 925 83

A series of benzoxazoles with a nitrogen-containing heterocyclic substituent at the 2-position was prepared and evaluated for 5-HT3 partial agonist activity on isolated guinea pig ileum. The nature of the substituent at the 5-position of the benzoxazole ring affected the potency for the 5-HT3 receptor, and the 5-chloro derivatives showed increased potency and lowered intrinsic activity. 5-Chloro-7-methyl-2-(4-methyl-1-homopiperazinyl)benzoxazole (6v) exhibited a high binding affinity in the same range as that of the 5-HT3 antagonist granisetron, and its intrinsic activity was 12% of that of 5-HT. Compound 6v inhibited 5-HT-evoked diarrhea but did not prolong the transition time of glass beads in the normal distal colon even at a dose of 100 times the ED50 for diarrhea inhibition in mice. Compounds of this type are expected to be effective for the treatment of irritable bowel syndrome without the side effect of constipation.
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PMID:Benzoxazole derivatives as novel 5-HT3 receptor partial agonists in the gut. 968 41

We studied effects of a novel alpha-2 adrenoceptor antagonist, YNS-15P (N-[(2R,11bS)-9-methoxy-1,3,4,6,7, 11b-hexahydro-2H-benzoquinolizin-2-yl]-N-methylmethanesulfonami de hydrochloride), on colonic propulsion stimulated by wrap-restraint stress (WRS) or bethanechol, on normal colonic propulsion and on diarrhea induced by castor oil in rats. Alpha-2 adrenoceptor antagonists, rauwolscine and RX821002, decreased the increase in the number and weight of fecal pellets induced by WRS. YNS-15P also inhibited WRS-stimulated fecal excretion in a dose-dependent manner. A 5-hydroxytryptamine3 receptor antagonist, granisetron, trimebutine and diazepam, but not a 5-hydroxytryptamine4 receptor antagonist, GR113808, significantly inhibited WRS-stimulated fecal excretion. YNS-15P inhibited WRS-stimulated colonic transit in a dose-dependent manner. However, YNS-15P had no significant effect on normal fecal excretion and colonic transit or on bethanechol-stimulated fecal excretion. YNS-15P also failed to inhibit castor-oil-induced diarrhea. These results indicate that YNS-15P selectively inhibits WRS-stimulated colonic propulsion, and that alpha-2 adrenoceptors may be involved in stress-induced colonic motor dysfunction in fed rats.
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PMID:Effect of YNS-15P, a new alpha-2 adrenoceptor antagonist, on stress-stimulated colonic propulsion in rats. 980 98

Although it is unclear to what extent irritable bowel syndrome (IBS) symptoms represent a normal perception of abnormal function or an abnormal perception of normal function, many believe that IBS constitutes the clinical expression of an underlying motility disorder, affecting primarily the mid- and lower gut. Indeed, transit and contractile abnormalities have been demonstrated with sophisticated techniques in a subset of patients with IBS. As a consequence, drugs affecting gastrointestinal (GI) motility have been widely employed with the aim of correcting the major IBS manifestations, ie, pain and altered bowel function. Unfortunately, no single drug has proven to be effective in treating IBS symptom complex. In addition, the use of some medications has often been associated with unpleasant side effects. Therefore, the search for a truly effective and safe drug to control motility disturbances in IBS continues. Several classes of drugs look promising and are under evaluation. Among the motor-inhibiting drugs, gut selective muscarinic antagonists (such as zamifenacin and darifenacin), neurokinin2 antagonists (such as MEN-10627 and MEN-11420), beta3-adrenoreceptor agonists (eg, SR-58611A) and GI-selective calcium channel blockers (eg, pinaverium bromide and octylonium) are able to decrease painful contractile activity in the gut (antispasmodic effect), without significantly affecting other body functions. Novel mechanisms to stimulate GI motility and transit include blockade of cholecystokinin (CCK)A receptors and stimulation of motilin receptors. Loxiglumide (and its dextroisomer, dexloxiglumide) is the only CCKA receptor antagonist that is being evaluated clinically. This drug accelerates gastric emptying and colonic transit, thereby increasing the number of bowel movements in patients with chronic constipation. It is also able to reduce visceral perception. Erythromycin and related 14-member macrolide compounds inhibit the binding of motilin to its receptors on GI smooth muscle and, therefore, act as motilin agonists. This antibiotic accelerates gastric emptying and shortens orocecal transit time. In the large bowel a significant decrease in transit is observed only in the right colon, which suggests a shift in fecal distribution. Several 'motilinomimetics' have been synthesized. Their development depends on the lack of antimicrobial activity and the absence of fading of the prokinetic effect during prolonged administration. 5-hydroxytryptamine (5-HT)4 agonists with significant pharmacological effects on the mid- and distal gut (such as prucalopride and tegaserod) are available for human use. These 'enterokinetic' compounds are useful for treating constipation-predominant IBS patients. 5-HT3 receptor antagonists also possess a number of interesting pharmacological properties that may make them suitable for treatment of IBS. Besides decreasing colonic sensitivity to distension, these drugs prolong intestinal transit and may be particularly useful in diarrhea-predominant IBS. Finally, when administered in small pulsed doses, octreotide, besides reducing the perception of rectal distension, accelerates intestinal transit, although other evidence disputes such an effect.
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PMID:Management of irritable bowel syndrome: novel approaches to the pharmacology of gut motility. 1020 10

There is evidence from studies, in both animals and humans, that 5-HT3 receptor blockade has potential value in the treatment of irritable bowel syndrome, particularly in those patients with diarrhoea-predominant bowel habits. New findings suggest that 5-HT3 receptors exist on gut afferent neurones and that their activation by locally released 5-HT leads to visceral nociceptive stimulation, in addition to increased neuronally-mediated motor and secretory activity. If this concept is validated, it will provide a rationale for the use of 5-HT3 receptor antagonists in patients with increased gut motility, reduced fluid absorption and low nociceptive thresholds leading to abdominal pain. Alosetron is a highly selective, potent 5-HT3 receptor antagonist which is well absorbed with a long pharmacodynamic half-life. Its ability to provide long-lasting blockade of 5-HT3 receptors throughout the body make it an ideal candidate within its class to evaluate the clinical hypothesis that sustained and ubiquitous 5-HT3 receptor blockade is of value in the treatment of IBS.
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PMID:Review article: the therapeutic potential of 5-HT3 receptor antagonists in the treatment of irritable bowel syndrome. 1042 38

Reinfusion of autologous hematopoietic peripheral blood stem cells (PBSC) or bone marrow is often accompanied by flushing, dyspnea, abdominal cramping, nausea and diarrhea. These symptoms and the observation that they can be prevented by ondansetron, a selective 5-HT3 receptor antagonist, led to the assumption that these side-effects are due to infusion of free serotonin during the reinfusion of PBSC or bone marrow. Twenty-five patients with solid tumors received, after myeloblative chemotherapy, a total of 30 reinfusions of PBSC and/or bone marrow. In 17 patients, serotonin levels in the bags containing the PBSC were measured. In all patients, platelet serotonin levels were determined before and 1 h post-reinfusion. In addition, before and 24 h after reinfusion urine was collected for determination of 5-hydroxyindole acetic acid (5-HIAA) and serotonin concentrations. Mean (+/- s.d.) total serotonin concentration in the bags was 2404 +/- 1555 nmol/l. Mean total volume reinfused was 471 +/- 185 ml. After reinfusion, the mean (+/- s.d.) levels of serotonin in platelets in patients increased from 3.2 +/- 1.4 nm/10(9) at baseline to 3.8 +/- 2.0 nm/10(9) (P = 0.02). Neither 24 h urinary 5-HIAA nor serotonin levels were affected. These results indicate that reinfusion of PBSC or bone marrow is accompanied by substantial infusion of free serotonin, which might explain the observed side-effects and justify the use of 5-HT3 receptor antagonists as pre- medication for this procedure.
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PMID:Effects of peripheral stem cell or bone marrow reinfusion on peripheral serotonin metabolism. 1055 62

Nearly 30% of patients treated with metformin experience gastrointestinal side effects. Since release of 5-hydroxytryptamine (5-HT) from the intestine is associated with nausea, vomiting, and diarrhea, we examined whether metformin induces 5-HT release from the intestinal mucosa. In 40% of tissue biopsy specimens of human duodenal mucosa, metformin (1, 10, and 30 microM) caused an increase in 5-HT outflow by 35, 70, and 98%, respectively. Peak increases in 5-HT outflow were observed after 10-15 min exposure to metformin, returning to baseline levels after 25 min. Tetrodotoxin (1 microM) reduced by about 50% the metformin-evoked increase in 5-HT outflow (P<0.05). Metformin-evoked release was not affected by scopolamine + hexamethonium, propranolol, the 5-HT3 receptor antagonist dolasetron, naloxone, or the NK1 receptor antagonist L703606. In the presence of tetrodotoxin (1 microM), somatostatin (1 microM) further reduced metformin-induced 5-HT release by 15-20%. In view of the 5-HT releasing effects of selective 5-HT3 receptor agonists to which metformin (N-N-dimethylbiguanide) is structurally related, we investigated whether metformin directly interacts with 5-HT3 receptors. Receptor binding (inhibition of [3H]-GR65630 binding) and agonist effects (stimulation of [14C]-guanidinium influx) at 5-HT3 receptors were studied in murine neuroblastoma N1E-115 cells, which express functional 5-HT3 receptors. Metformin up to 0.3 mM failed to inhibit [3H]-GR65630 binding and to modify displacement of [3H]-GR65630 binding induced by 5-HT. 5-HT (3 microM) stimulated the influx of [14C]-guanidinium in intact N1E-115 cells. Metformin up to 1 mM failed to modify basal influx, 5-HT-induced influx, and 5-HT+ substance P-induced influx of [14C]-guanidinium. Our results indicate that metformin induces 5-HT3 receptor-independent release of 5-HT from human duodenal mucosa via neuronal and non-neuronal mechanisms. Part of the gastrointestinal side effects observed during treatment with metformin could, thus, be produced by the release of 5-HT and other neurotransmitter substances within the duodenal mucosa.
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PMID:Effects of metformin on intestinal 5-hydroxytryptamine (5-HT) release and on 5-HT3 receptors. 1065 Nov 52

Alosetron is a potent and highly selective serotonin 5-HT3 receptor antagonist which has been evaluated for the management of irritable bowel syndrome (IBS). It blocked the fast 5HT3-mediated depolarisation of guinea-pig myenteric and submucosal neurons in vitro, with half-maximal inhibition at approximately 55 nmol/L. Alosetron attenuated the visceral nociceptive effect of rectal distension in conscious or anaesthetised dogs. It increased the compliance of the colon to distension in patients with IBS and delayed colonic transit in patients with IBS or carcinoid diarrhoea and in healthy volunteers. A single dose of alosetron 4 mg increased in vivo fluid absorption in normal human small intestine. In clinical trials in patients with IBS, alosetron 1 mg twice daily was effective in relieving abdominal pain and discomfort. Alosetron was most effective in female patients and particularly in those with diarrhoea-predominant IBS. In patients with IBS and healthy volunteers who received alosetron, the most common adverse event was constipation.
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PMID:Alosetron. 1077 33

The irritable bowel syndrome (IBS) is one of the most common gastrointestinal conditions encountered by general practitioners, and it accounts for a great deal of the workload of gastroenterologists in secondary care. Research to date indicates that several factors contribute to the development of IBS, of which disturbed gastrointestinal motility, altered visceral perception and psychosocial factors are regarded as the three most important mechanisms interacting in the development of this disorder. Most pharmacological research has been based on these insights. Several agents capable of modulating either motility or sensitivity are currently under investigation. Potential drugs in the treatment of diarrhoea-predominant IBS are the more selective antispasmodics, such as the M3-receptor antagonists (e.g. zamifenacin, darifenacin). In constipation-predominant IBS the colokinetic effects of the selective 5HT4 agonists prucalopride and tegaserod are of great interest. Since altered visceral perception is thought to play an important role in the genesis of abdominal pain and bloating in many patients with IBS, new drugs are targeted at modulating the sensitivity, such as 5HT3 antagonists (e.g. alosetron), kappa-agonists (e.g. fedotozine) and somatostatin analogues. Furthermore, psychosocial factors should not be overlooked, since these appear to be of great influence on the clinical outcome of IBS.
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PMID:New developments in the treatment of irritable bowel syndrome. 1123 89

Although the past few years have seen an exponential growth of compounds of potential interest for the treatment of functional gastrointestinal (GI) tract disorders, the gap that still exists between basic and clinical research is easily noticed if one considers the relative paucity of drugs that have received marketing authorisation for the treatment of irritable bowel syndrome (IBS). Traditional efficacy outcomes in drug development for IBS include the ability of the compound to affect GI tract motility (i.e. to exert a prokinetic or an antispasmodic effect), which is thought to be of importance if a motor disorder is the underlying pathophysiological mechanism. More recently, altered visceral sensitivity to a distending stimulus has been suggested to be a key pathophysiological feature, at least in some patients, and has become a target for therapeutic interventions. However, there is now growing consensus that the primary outcome measure in the treatment of functional disorders are those that reflect overall control of the patient's symptoms (pain, diarrhoea, constipation) in everyday situations such as the clinical global improvement scales. Although, in general, guidelines on the design of treatment trials for functional GI tract disorders advise against subcategorisation of patients according to the main symptom (because of symptom instability), subcategorisation indeed makes sense especially in IBS (constipation- or diarrhoea-predominant). Compounds with a specific indication for each subpopulation of patients are now emerging. The rationale for investigations on serotonin (5-hydroxytryptamine; 5-HT) receptor ligands in IBS rests mainly on the fact that serotonin, which may be released by enterochromaffin-like cells in the GI tract as well as from other sources, has a number of well documented motor effects on the GI tract and can produce hyperalgesia in several experimental models. Serotonin receptors belonging to the 5-HT3 and 5-HT4 subtype are the most extensively studied in gastroenterology, although hitherto 'orphan' receptor subtypes, such as the 5-HT7 and the 5-HT(1B/D) receptors, are now emerging. Among 5-HT3 receptor antagonists, alosetron was recently approved for the treatment of diarrhoea-predominant IBS and is an example of a compound that, at least theoretically, may act at multiple levels: by inhibiting visceral sensitivity, by increasing compliance, and by inhibiting excitatory 5-HT3 receptors located on both ascending and descending neuronal pathways involved in peristalsis. For this reason, 5-HT3 receptor antagonists may slow transit, hence the specific indication of alosetron in diarrhoea-predominant IBS. However, alosetron has been recently withdrawn by the manufacturer because of safety concerns. Hypomotility remains an attractive therapeutic target in IBS and the new generation of prokinetics includes several partial agonists at the 5-HT4 receptor, such as tegaserod (HTF-919) and prucalopride (R0-93877). In addition, preliminary evidence suggests that 5-HT4 receptors may also be involved in the modulation of visceral sensitivity. Second-generation 5-HT4 receptor agonists seem to be devoid of the QT-prolonging effects observed in some clinical circumstances with cisapride and may be more active at the colonic level. Piboserod (SB-207266A) is a 5-HT4 receptor antagonist under development for the treatment of diarrhoea-predominant IBS. Finally, interest in 5-HT7 and 5-HT(1B/D) receptor subtypes stems from the observation that the former receptors mediate smooth muscle relaxation (at least in the human colon), whereas sumatriptan (a 5-HT(1B/D) receptor agonist) can affect GI tract motility and visceral sensitivity.
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PMID:Irritable bowel syndrome: new agents targeting serotonin receptor subtypes. 1129 43


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