Tegaserod coadministration does not alter the pharmacokinetics of theophylline in healthy subjects

Tegaserod for constipation-predominant irritable bowel syndrome

Tegaserod, a selective and partial agonist at the 5-hydroxytryptamine (5-HT [serotonin]) receptor subtype 4 (5-HT4), is the only United States Food and Drug Administration-approved drug for the treatment of constipation-predominant irritable bowel syndrome (IBS) in women. The drug's stimulation of 5-HT4 receptors on intestinal enterocytes increases peristaltic activity and fluid secretion into the gut lumen, facilitating stool passage. In addition, affinity of tegaserod for 5-HT4 receptors modulates visceral sensitivity, which helps alleviate abdominal pain associated with constipation-predominant IBS. The drug's pharmacokinetic and pharmacodynamic parameters do not differ significantly with age or sex. Tegaserod safely and effectively relieves overall gastrointestinal symptoms and abdominal discomfort and normalizes bowel habits in patients with constipation-predominant IBS. It is associated with few drug interactions. In clinical studies, tegaserod was well tolerated, and its adverse-effect profile was similar to that of placebo. Severe diarrhea, as well as abdominal pain, flatulence, headache, and nausea, were the most commonly reported events. Patients who experience severe diarrhea should discontinue the drug. With the data available, tegaserod remains an option for patients with constipation-predominant IBS.

Tegaserod in the treatment of irritable bowel syndrome (IBS) with constipation as the prime symptom

Irritable bowel syndrome with constipation (IBS-C) as the predominant bowel symptom is a prevalent disorder, characterized by recurring abdominal pain/discomfort, bloating, and constipation, and imposes a significant socio-economic burden. Traditional treatments generally address just one of the multiple IBS symptoms. The efficacy and safety profile of tegaserod, a serotonin 5-HT(4) receptor agonist, has been demonstrated in several randomized, placebo-controlled, and open-label trials. This review discusses the major clinical trials of tegaserod, which have involved 8948 IBS patients. Overall, data reveal that tegaserod is an effective treatment for IBS-C, providing statistically significant relief of overall and multiple individual IBS-C symptoms (abdominal pain/discomfort, bloating, and constipation) in both placebo-controlled and "real-life" open-label settings. Repeat treatments with tegaserod were also shown to be effective, which is noteworthy given the chronic and episodic nature of IBS. Moreover, tegaserod was associated with improvements in patients' quality of life and work productivity. Data also indicate that tegaserod is well tolerated over the short-term (4 weeks), long-term (12 months), and repeated treatments. Diarrhea is the only adverse event consistently associated with tegaserod and was generally mild and transient. Overall, tegaserod has been demonstrated to offer effective and well-tolerated treatment of IBS-C, providing patients with meaningful symptom relief.

Safety and tolerability of tegaserod in patients with chronic constipation: pooled data from two phase III studies

BACKGROUND & AIMS

Studies show that tegaserod effectively relieves the symptoms of chronic constipation/idiopathic constipation (CC). This pooled analysis assessed the safety and tolerability of tegaserod in a large dataset of CC patients.

METHODS

Adverse event (AE) data were pooled from 2 double-blind, placebo-controlled phase III trials of 12 weeks' duration. Post hoc analysis was conducted for the most frequent AEs (incidence, >or=3%).

RESULTS

Eight hundred eighty-one, 861, and 861 patients received tegaserod 6 mg twice a day, 2 mg twice a day, or placebo, respectively. Most AEs were mild/moderately severe. AE incidence was similar for the tegaserod 6 mg and 2 mg twice a day (57.1% and 56.3%, respectively) and placebo groups (59.6%) and most frequent in the gastrointestinal system (tegaserod 6 mg twice a day, 25.8%; 2 mg twice a day, 22.5%; placebo, 24.6%). Headache, the most common AE, was slightly more frequent in the placebo group (tegaserod 6 mg twice a day, 11.0%; 2 mg twice a day, 10.1%; placebo, 13.2%). Diarrhea (generally transient and resolved with continued treatment) was the only AE with a statistically significant difference between groups (tegaserod 6 mg twice a day 6.6% vs placebo 3.0%, P=.0005). Serious AE incidence (1.4% overall) was comparable across treatment groups, although abdominal surgery was less common in the combined tegaserod (0.5%) than the placebo group (1.0%). Discontinuation as a result of AEs was slightly higher in tegaserod 6 mg twice a day patients (5.7%; 2 mg twice a day, 3.3%; placebo, 3.7%), mainly because of diarrhea. Laboratory and electrocardiogram parameters were comparable across groups.

CONCLUSIONS

Tegaserod is well tolerated by patients with CC during 12 weeks of treatment.

The rationale, efficacy and safety evidence for tegaserod in the treatment of irritable bowel syndrome

A growing body of evidence implicates abnormal serotonergic regulation of gastrointestinal function in the pathogenesis of the irritable bowel syndrome (IBS). Drugs targeting this system are therefore attractive concepts. The partial 5-HT4 receptor agonist tegaserod might be predicted to have positive therapeutic effects on a constipated and uncomfortable gut. However, IBS runs a chronic, benign course and carries no associated mortality, so it is imperative that the safety profile of new pharmacological agents made available to physicians is exemplary. The authors review the evidence for 5-HT in the aetiology of IBS and its symptoms, and the data available concerning the partial 5-HT4 receptor agonist tegaserod, in terms of rationale, efficacy and safety.

Theophylline pharmacokinetics: comparison of Cyp1a1(-/-) and Cyp1a2(-/-) knockout mice, humanized hCYP1A1_1A2 knock-in mice lacking either the mouse Cyp1a1 or Cyp1a2 gene, and Cyp1(+/+) wild-type mice

OBJECTIVES

Pharmacokinetics of theophylline was investigated in Cyp1(+/+) wild-type mice, Cyp1a1(-/-) and Cyp1a2(-/-) knockout mice, and humanized hCYP1A1_1A2 mice lacking either the mouse Cyp1a1 or Cyp1a2 gene.

METHODS AND RESULTS

Animals received a single dose of theophylline (8 mg/kg i.p.), either alone or pretreated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD; 10 microg/kg i.p.) 24 h prior to theophylline. We found that mouse or human CYP1A2 is the predominant enzyme for theophylline metabolism, the contribution of mouse or human CYP1A1 to theophylline metabolism is negligible, and another TCDD-inducible enzyme plays a minor role in 1-methyluric acid and 1,3-dimethyluric acid formation as well as enhanced theophylline clearance from the body. The half-life of elimination from plasma was more than four times longer in Cyp1a2(-/-) than Cyp1(+/+) mice and more than 10 times different after TCDD pretreatment. In humanized hCYP1A1_1A2 mice lacking the mouse Cyp1a2 gene, the half-life of elimination from plasma was two to three times longer than that in Cyp1(+/+) mice and four to five times different after TCDD pretreatment.

CONCLUSION

Replacement of mouse Cyp1a2 with a functional human CYP1A2 gene restored the ability to metabolize theophylline, and the metabolism changed to a humanized profile (i.e. 3-methylxanthine formation, not seen in the wild-type mouse). TCDD-pretreated hCYP1A1_1A2 Cyp1a2(-/-) mice exhibited enhanced theophylline metabolism and clearance, due to induction of the human CYP1A2 enzyme. Comparing the hCYP1A1_1A2 Cyp1a2(-/-) and wild-type mice with published clinical studies, we found theophylline clearance to be about 5 times and 12 times, respectively, greater than that reported in humans.

Safety and tolerability of tegaserod in irritable bowel syndrome management

OBJECTIVES

To discuss the need for safe and effective therapy for patients with irritable bowel syndrome (IBS) and to provide up-to-date information on the safety and tolerability profile of tegaserod, a novel treatment for women with IBS whose primary bowel symptom is constipation.

DATA SOURCES

PubMed and abstracts from gastroenterology conferences were searched through October 2003 using the following search terms: irritable bowel syndrome, IBS, tegaserod, cisapride, alosetron, systematic review, safety, tolerability, serotonin, 5-HT, 5-HT3 receptor antagonist, and 5-HT4 receptor agonist; all information on the safety and tolerability of tegaserod published up to October 2003 is included.

DATA SYNTHESIS

A comprehensive review of the medical literature (through 2001) finds no adequate therapies that address the multiple symptoms of IBS. Traditional agents, although occasionally effective, often cause adverse effects. Tegaserod, a selective serotonin type 4 receptor (5-HT4) partial agonist, overcomes a number of obstacles associated with traditional therapies. Important information for pharmacists about the safety and tolerability of tegaserod is presented.

CONCLUSION

Tegaserod is effective in treating multiple IBS symptoms in women with IBS whose primary bowel symptom is constipation, and it is safe and well tolerated.

Safety Profile of Tegaserod, a 5-HT4 Receptor Agonist, for the Treatment of Irritable Bowel Syndrome

This article reviews the safety and tolerability profile of tegaserod, a novel selective partial agonist of the serotonin 5-HT(4) receptor. Tegaserod was recently approved for the treatment of women with irritable bowel syndrome (IBS) with constipation. Tegaserod exhibits rapid absorption from the small intestine, and is excreted unchanged in the faeces and as metabolites in the urine. Meal ingestion decreases its bioavailability. There is little effect of age or gender on pharmacokinetics, although plasma levels may be slightly higher in the elderly. Tegaserod has no effect on plasma levels of other drugs metabolised by cytochrome P450 enzyme systems. Gastrointestinal symptoms are the most common adverse effects of tegaserod therapy. In data pooled from phase III randomised controlled trials (RCTs) in IBS with constipation patients, diarrhoea was reported by 8.8% of patients treated with tegaserod 6mg twice daily versus 3.8% of patients receiving placebo. Similar rates have been observed in international post-US marketing RCTs. In most patients, tegaserod-induced diarrhoea was mild and transient. In RCTs, it did not elicit fluid or electrolyte disturbances, and fewer than 3% of IBS patients discontinued tegaserod due to diarrhoea. Since its release, rare cases of more severe diarrhoea and ischaemic colitis have been reported. The incidence of other gastrointestinal symptoms (e.g. abdominal pain, nausea, and flatulence) has been similar among tegaserod-treated patients and placebo-treated patients. Pooled analysis of phase III RCTs and post-US marketing RCTs have not demonstrated significant differences between tegaserod-treated patients and placebo-treated patients in the incidence of abdominal-pelvic surgery. There is no convincing evidence that rebound gastrointestinal symptoms occur upon termination of tegaserod therapy. Pooled analysis of phase III RCTs demonstrated an increase in the incidence of headaches among tegaserod-treated patients (6mg twice daily) compared with placebo-treated patients (15% vs 12.3%, respectively, p < 0.05), although post-US marketing RCTs have not observed this increase. Other extra-gastrointestinal adverse events occur with similar frequency among tegaserod-treated patients and placebo-treated patients. Tegaserod-treated patients in RCTs have not demonstrated significant prolongation of the QTc interval or cardiac arrhythmias compared with placebo-treated patients. Supra-therapeutic doses in healthy volunteers did not effect electrocardiographic parameters. Laboratory parameters are mostly unaffected by tegaserod, although several individuals have exhibited increased eosinophil counts. In summary, tegaserod exhibits a favourable safety and tolerability profile in IBS patients based on data from clinical trials. Diarrhoea is the most common adverse event associated with tegaserod use. Continued post-US marketing surveillance will further define the safety and tolerability profile of tegaserod.

Benefit-Risk Assessment of Tegaserod in Irritable Bowel Syndrome

Tegaserod is a new partial agonist of serotonin 5-HT4 receptors specifically developed for the treatment of nondiarrhoeal forms of irritable bowel syndrome (IBS). Among its various effects is the stimulation of the peristaltic reflex with its promotility action appearing to affect the whole length of the gastrointestinal tract. Tegaserod has been assessed in a number of international multicentre trials and its use leads to an improvement in abdominal pain and bowel dysfunction as well as global well-being, at the expense of remarkably few adverse effects. It is noteworthy that it also appears to improve bloating, a benefit that has not been previously reported for a medication used in IBS. The optimal dose is 6 mg twice daily and the advantage of tegaserod over placebo in different trials varies from 5-20% with the number needed to treat ranging from 5-15 depending on the time at which this effect is calculated during the course of a trial. Recent experience with other drugs acting on 5-HT receptors has focused attention on possible safety issues such as prolongation of the QTc interval on the electrocardiogram and ischaemic colitis. However, data from efficacy trials and studies specifically designed to address the safety of tegaserod have not revealed any evidence of cardiotoxicity or the potential for causing ischaemic colitis. Furthermore, investigation of possible interactions with other drugs such as warfarin or the oral contraceptive have not resulted in any prescribing restrictions. Inappropriate prescription of tegaserod to a subgroup of IBS patients for which the drug was not designed, does not appear to have any serious consequences. Most of the efficacy data on tegaserod has been accumulated in females, simply as a result of the failure to recruit adequate numbers of males or restriction of trials to females. There is therefore insufficient information to assess whether there might be any potential gender differences in responsiveness. For this reason, the drug is currently only licensed for use in females.

Tegaserod: a review of its use in the management of irritable bowel syndrome with constipation in women

The treatment of irritable bowel syndrome with constipation (IBS-C) has historically been based on the severity of symptoms, with education, reassurance, dietary advice, bulking agents and laxative therapy offered as appropriate. Tegaserod (Zelnorm, Zelmac) is the first selective serotonin 5-HT(4) receptor partial agonist to be approved for the treatment of this syndrome. Tegaserod is active against multiple irritable bowel syndrome (IBS) symptoms; it stimulates gut motility and reduces visceral sensitivity and pain. The drug does not cure IBS and was not designed to treat the diarrhoea-predominant version. Its efficacy in men has not been established. Three large well designed clinical trials of tegaserod 6 mg twice daily for 12 weeks in patients (mainly women) with IBS-C have demonstrated superiority versus placebo in global relief from symptoms. Global relief response rates were 38.4-46.8% with tegaserod 6 mg twice daily and 28.3-38.8% with placebo (p < 0.05-0.0001 vs placebo). The relative increases in response rates with tegaserod 6 mg twice daily over the already high responses in the placebo groups ranged from 12-65% after 4-12 weeks of treatment. A response was seen within the first week. The proportion of patients with satisfactory relief from symptoms fell over the 4-week period following withdrawal of tegaserod and placebo, but did not reach baseline levels during this time. Diarrhoea has been associated with tegaserod in clinical trials (an incidence of about 10% versus 5% with placebo, usually occurring in the first week of treatment), but the drug is otherwise well tolerated. There were no apparent changes in the tolerability profile with extended tegaserod treatment (</=12 months). In conclusion, oral tegaserod 6 mg twice daily for 12 weeks is effective and well tolerated in the treatment of IBS-C in women. Data on long term and comparative efficacy, cost-effectiveness and quality-of-life effects would be beneficial; however, in light of the fact that very few alternatives for the treatment of IBS-C have proven efficacy, tegaserod appears to be a promising option in women not responding to increased dietary fibre or osmotic laxative therapy.

Tegaserod maleate in the treatment of irritable bowel syndrome: a clinical review

BACKGROUND

Approved in July 2002, tegaserod maleate is a partial 5-hydroxytryptamine 4-receptor agonist used to improve symptoms of constipation-predominant irritable bowel syndrome (IBS). The physiologic actions of tegaserod relate to its ability to stimulate gastric and intestinal motility.

OBJECTIVE

This article reviews available data on the pharmacokinetic and pharmacodynamic properties and clinical efficacy of tegaserod.

METHODS

Searches of MEDLINE and PubMed from 1966 to the present were conducted using the search terms tegaserod, tegaserod maleate, irritable bowel syndrome, and Rome criteria. Abstracts presented at national meetings between 1997 and 2002 were reviewed and included if perceived to be reliable and relevant.

RESULTS

In clinical trials, tegaserod was associated with significantly better scores on the subject's global assessment of relief compared with placebo (P < 0.05). The absolute efficacy of tegaserod compared with placebo varied between trials and averaged 10% to 12%. Tegaserod had a good safety profile; diarrhea was the only adverse effect that occurred more often in tegaserod recipients than in placebo recipients. No electrocardiographic changes were observed at therapeutic concentrations of tegaserod. Long-term (1-year) treatment with tegaserod appeared to be well tolerated. The recommended dosage for patients aged >18 years with constipation-predominant IBS is 6 mg PO BID before meals for 4 to 6 weeks, with an additional 4 to 6 weeks of treatment if initial therapy is partially effective.

CONCLUSIONS

The addition of tegaserod to the arsenal of moderately effective medication currently used in the treatment of IBS may be helpful in patients with constipation-predominant IBS. Continuous postmarketing surveillance and reporting of adverse reactions are essential to further characterize the safety profile of this new agent.

Clinical pharmacokinetics of tegaserod, a serotonin 5-HT(4) receptor partial agonist with promotile activity

Tegaserod, a selective serotonin (5-hydroxytryptamine; 5-HT) 5-HT(4) receptor partial agonist, is indicated in patients with irritable bowel syndrome (IBS) who identify abdominal pain or discomfort and constipation as their predominant symptoms. Tegaserod at dosages of 1 to 12 mg/day exerts pharmacodynamic actions in the upper and the lower gastrointestinal tract, accelerating small bowel and colonic transit in patients with IBS. Tegaserod is rapidly absorbed following oral administration; peak plasma concentrations (C(max)) are reached after approximately 1 hour. Absolute bioavailability is about 10% under fasted conditions. Food reduces the bioavailability of tegaserod by 40 to 65% and the C(max) by 20 to 40%. Systemic exposure to tegaserod is not significantly altered at neutral gastric pH compared with the fasted state (pH 2). Tegaserod is approximately 98% bound to plasma proteins, primarily to alpha(1)-acid glycoprotein, and has a volume of distribution at steady-state of 368 +/- 223L. Tegaserod is metabolised mainly via two pathways. The first is a presystemic acid-catalysed hydrolysis in the stomach followed by oxidation and conjugation which produces the main metabolite of tegaserod, 5-methoxyindole-3-carboxylic acid glucuronide (M 29.0). This metabolite has negligible affinity for 5-HT(4) receptors and is devoid of promotile activity. The second is direct glucuronidation which leads to generation of three isomeric N-glucuronides. The plasma clearance of tegaserod is 77 +/- 15 L/h, with an estimated terminal half-life of 11 +/- 5 hours following intravenous administration. Approximately two-thirds of the orally administered dose of tegaserod is excreted unchanged in faeces, with the remainder excreted in urine, primarily as M 29.0. The pharmacokinetics of tegaserod are dose-proportional over the range 2 to 12mg given twice daily for 5 days, with no relevant accumulation. The pharmacokinetics of tegaserod in patients with IBS are comparable to those in healthy individuals, and similar between men and women. No dosage adjustment is required in elderly patients or those with mild to moderate hepatic or renal impairment. Tegaserod should not be used in patients with severe hepatic or renal impairment. No clinically relevant drug-drug interactions with tegaserod have been identified. In vivo drug-drug interaction studies with theophylline [a cytochrome P450 (CYP) 1A2 prototype substrate], dextromethorphan (a CYP2D6 prototype substrate), digoxin, warfarin and oral contraceptives have indicated no clinically relevant interactions and no requirement for dosage adjustment.