5-HT3 Receptor

The present study was designed to evaluate the anti-inflammatory effect of Alosetron, a 5-HT3R antagonist, on trinitrobenzenesulfonic acid (TNBS)-induced ulcerative colitis in rats. Two h subsequent to induce colitis (intracolonic instillation of TNBS, 50 mg/kg) in male Wistar rats, alosetron (1 mg/kg), dexamethasone (1 mg/kg), meta-chlorophenylbiguanide (mCPBG, a 5-HT3R agonist, 5 mg/kg), or alosetron + mCPBG were administrated intraperitoneally for 6 days. Animals were thereafter sacrificed and the efficacy of drugs was evaluated macroscopically, histologically, and biochemically (myeloperoxidase, tumor necrosis factor-alpha, interleukin-6, and interleukin-1 beta) on distal colon samples. Treatment with alosetron and dexamethasone improved macroscopic and microscopic colonic damages significantly and decreased myeloperoxidase activity and colonic levels of inflammatory cytokines. The profitable effects of alosetron were antagonized by concurrent administration of mCPBG. Our data provided evidence that the protective effects of alosetron on TNBS-induced colitis can be mediated by 5- HT3R. [7]

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Diarrhea index was considerably reduced in rats treated with dexamethasone and Alosetron (1 mg/kg; i.p.; daily for 6 days) compared with the TNBS control group, notably during the first 2 days of treatment after induction of colitis return.

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Irritable bowel syndrome, which affects 5–10% of the population includes around 25% with predominantly diarrhoea (IBS-D). Several lines of evidence suggest an increase in mucosal 5-HT availability in IBS-D including a decrease in the serotonin transporter (SERT) which is also seen following acute diverticulitis. 5-HT3 receptor antagonists have proved effective in suppressing urgency, prolonging small and large bowel transit and relieving symptoms in IBS-D. Alosetron continues to be used under restricted availability without any serious morbidity despite ischemic colitis which occurs at a rate of <1/1000 patient year. Other agents such as ramosetron and ondansetron are still in use and have not been associated with ischemic colitis. 5-HT3 receptor agonists stimulate intestinal motility, shorten transit times and in a pilot trial accelerated transit in patients with IBS-C. [1]

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Irritable bowel syndrome (IBS) is a highly prevalent functional gastrointestinal disorder that causes a range of symptoms. Currently, Alosetron hydrochloride (Lotronex®), a selective serotonin type 3 receptor antagonist, is the only medication approved for the treatment of severe diarrhea-predominant irritable bowel syndrome (IBS-D) in women who have inadequately responded to conventional therapy. Alosetron has demonstrated efficacy compared with placebo in clinical trials and has been shown to improve overall health-related quality of life (HRQoL). However, rare instances of ischemic colitis and severe complications of constipation have been reported. As a result, in 2000 alosetron was voluntarily withdrawn from the market but was reintroduced in 2002 with a more restricted indication and a requirement that clinicians and patients follow a prescribing program. Although the efficacy and benefit of alosetron has been clearly demonstrated, it has been used sparingly since its reintroduction. This brief review describes the history of Alosetron, efficacy of alosetron in the treatment of IBS, the impact of severe IBS on HRQoL, safety considerations, the risk evaluation and mitigation strategy program under which alosetron is now prescribed, and an update on postmarketing surveillance data. [2]

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Irritable bowel syndrome affects 5-10% of North Americans, with an estimated one-third having a diarrhea-predominant form. Alosetron hydrochloride (Lotronex) is a serotonin receptor type 3 antagonist approved in early 2000 for use in women with diarrhea-predominant irritable bowel syndrome (IBS-D). Initial use was widespread, but infrequent serious adverse events of ischemic colitis and severe constipation-related complications prompted alosetron's voluntary withdrawal from the US market in November 2000. Unprecedented public request prompted its reintroduction in 2002 under a Risk Management Plan, including a more restricted indication and a Prescribing Program for Lotronex. Despite these measures, the use of alosetron has been very limited since its reintroduction. Possible deterrents to its use include concerns over safety and the possible medical-legal implications raised by the Risk Management Plan. It is also possible that changes in the natural history and/or diagnosis of IBS-D have reduced the target population. Given the unique regulatory history of Alosetron, these issues continue to engender controversy. This article profiles these concerns and reviews the pharmacology, clinical efficacy and safety, and post-marketing experience with alosetron. Myths and misconceptions related to alosetron use, or lack thereof, are addressed to provide the reader with the evidence needed to make informed treatment decisions for their female patients with severe IBS-D [3].

Rats were randomly divided into six groups of 6 in each and following treatments were administered: (I) TNBS-control group, rats received normal saline (intraperitoneally, ip) 2 h subsequent to induction of colitis; (II) normal group, animals were administered normal saline intracolonically instead of TNBS; (III) dexamethasone group, dexamethasone (1 mg/kg, ip) was given 2 h following induction of colitis; (IV) Alosetron group, Alosetron (1 mg/kg, ip) was given 2 h following induction of colitis; (V) mCPBG group, mCPBG (5 mg/kg, ip), was administered 2 h following induction of colitis; (VI) Alosetron + mCPBG group, Alosetron and mCPBG were concurrently given (ip) 2 h following induction of colitis. All treatment continued daily for 6 days. [7]

Absorption, Distribution and Excretion
Absorption is rapid after oral administration, with an absorption rate ranging from 30% to over 90%. /Unspecified salt/ Alosetron…is rapidly absorbed after oral administration and widely distributed in tissues in animals after oral or intravenous administration. Its metabolism is rapid and extensive, including N-demethylation, hydroxylation, and oxidation. The drug or its two major metabolites are excreted via the biliary tract and kidneys. Alosetron has been shown to be safe in a series of toxicity studies; clinical symptoms are transient even with repeated administration of high doses, and repeated administration has not had a significant adverse effect on fertility, reproductive function, or fetal development. In pharmacokinetic studies, the bioavailability of alosetron in healthy volunteers is approximately 60%, and the plasma half-life is approximately 1.5 hours. There are some sex differences in the pharmacokinetic characteristics of alosetron, with concentrations in women being 30-50% higher than in men. No significant differences in serum alosetron concentrations were observed between young and old individuals. The pharmacokinetics of a single oral dose of alosetron are linear up to 8 mg. .../Unspecified salt/

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Metabolism/Metabolites
/Alosetron is rapidly and extensively metabolized, including N-demethylation, hydroxylation, and oxidation. The drug or its two main metabolites are excreted via the biliary tract and kidneys. Alosetron has been shown to be safe in a series of toxicity studies; clinical symptoms are transient even with repeated administration of high doses, and repeated administration has not had a significant adverse effect on fertility, reproductive function, or fetal development. .../Unspecified salt/
Alosetron is primarily metabolized by a variety of cytochrome P450 (CYP) enzymes, including CYP2C9 and CYP3A4.

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Biological half-life
The plasma half-life is approximately 1.5 hours.

Interactions
…A study aimed to investigate whether alosetron could alter the pharmacokinetics of theophylline by inhibiting its metabolism, based on its effects on CYP1A2 activity in vitro and in vivo. …In this randomized, placebo-controlled, two-way crossover study, 10 healthy female volunteers received either theophylline 200 mg twice daily for 8 days alone or alosetron 1 mg twice daily for 15 days concurrently. …Alosetron had no significant effect on theophylline plasma concentrations (Cmax approximately 9 μg/ml, AUC approximately 90 μg/ml·hr) or the oral clearance of the three major metabolites (3-methylxanthine, 1-methyluric acid, and 1,3-dimethyluric acid) metabolized by CYP1A2 (5, 7, and 16 ml/min, respectively). Concomitant administration of alosetron and theophylline was well tolerated. …In vitro and in vivo metabolic probe data did not predict a clinical drug interaction of alosetron inhibiting theophylline metabolism. /Unspecified Salt/ PMID:11736869
Locetron (alosetron hydrochloride) is a 5-HT3 receptor antagonist indicated for the treatment of irritable bowel syndrome (IBS) in women with diarrhea as the predominant symptom. Alosetron is primarily metabolized by a variety of cytochrome P450 (CYP) enzymes, including CYP2C9 and CYP3A4. Fluoxetine is an antidepressant administered as a racemic mixture of equivalent R- and S-enantiomers. The formation of the major metabolite of fluoxetine, norfluoxetine, involves CYP2D6 and CYP2C9. This metabolite exists in two enantiomers, of which only the S-enantiomer possesses comparable antidepressant activity. This study aimed to evaluate the potential impact of alosetron on the pharmacokinetics of fluoxetine. This was an open-label, two-period, non-randomized, crossover study that included 12 healthy male and female volunteers. The pharmacokinetics of fluoxetine and its enantiomers (S- and R-fluoxetine or S- and R-norfluoxetine) were assessed after a single oral dose of 20 mg fluoxetine (alone) and in combination with alosetron 1 mg twice daily for 15 days. Results showed that alosetron had no significant effect on the pharmacokinetics of S- and R-fluoxetine or S- and R-norfluoxetine, but a slight delay in peak concentration. All subjects tolerated the combination of alosetron and fluoxetine well. PMID: 11304903
Loterone (alosetron hydrochloride) is a 5-HT3 receptor antagonist indicated for the treatment of irritable bowel syndrome (IBS) in women with predominantly diarrhea-related symptoms. Alosetron is primarily metabolized by various cytochrome P450 (CYP) enzymes, including CYP2C9 and 3A4. Alprazolam is a short-acting benzodiazepine commonly used to treat anxiety disorders and may also be a potential concomitant medication for IBS patients. Alprazolam is primarily metabolized via CYP3A4. This clinical study aimed to evaluate potential metabolic drug interactions between these two CYP3A4 substrates. This was an open-label, randomized, two-period, crossover study involving 12 healthy male and female volunteers, designed to determine the effect of concomitant administration of alosetron at a recommended dose (1 mg/oral, twice daily) on the pharmacokinetics of alprazolam following a single oral dose of 1 mg. Results showed that alosetron had no effect on the pharmacokinetics of alprazolam. The mean AUC of alprazolam was 210 ng/h/ml in the absence of alosetron and 202 ng/h/ml in the presence of alosetron. Therefore, alprazolam can be safely co-administered with alosetron without dose adjustment. PMID: 11304902

[1]. Targeting the 5-HT3 receptor in the treatment of irritable bowel syndrome By Spiller, Robin C. From Current Opinion in Pharmacology (2011), 11(1), 68-74.

[2]. Optimizing outcomes with alosetron hydrochloride in severe diarrhea-predominant irritable bowel syndrome. Therap Adv Gastroenterol. 2010 May;3(3):165-72.

[3]. Alosetron for severe diarrhea-predominant irritable bowel syndrome: safety and efficacy in perspective. Expert Rev Gastroenterol Hepatol. 2010 Feb;4(1):13-29.

[4]. Acute hepatitis associated with alosetron (Lotronex). J Clin Gastroenterol. 2005 Aug;39(7):641-2.

[5]. Incidence of colonic ischemia, hospitalized complications of constipation, and bowel surgery in relation to use of alosetron hydrochloride. Am J Gastroenterol. 2003 May;98(5):1117-22.

[6]. Alosetron. Drugs. 2000;59(3):511-520.

[7]. Anti-inflammatory effects of alosetron mediated through 5-HT3 receptors on experimental colitis. Res Pharm Sci. 2019;14(3):228-236.

Alosetron hydrochloride is the hydrochloride form of Alosetron, a potent and selective 5-HT3 receptor antagonist. Alosetron blocks the action of serotonin at 5-HT3 receptor sites in the peripheral nervous system, particularly in the gut and nociceptive neurons, thereby affecting the regulation of visceral pain, reducing gastrointestinal contractions and peristalsis, and decreasing gastrointestinal secretions. This drug is used to treat diarrhea-predominant irritable bowel syndrome in women.
See also: Alosetron (containing the active ingredient).

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Mechanism of Action
Serotonin 5-HT3 Receptor Antagonist/Unspecified Salt/
……5-HT3 receptor antagonists delay colonic transit, increase colonic compliance, and increase the absorption of water in the small intestine. ……/Unspecified Salt/
Alosetron is a potent and highly selective 5-HT(3) receptor antagonist. ……

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Alosetron hydrochloride is the hydrochloride form of Alosetron, a potent and selective 5-HT3 receptor antagonist. Alosetron blocks the action of serotonin at 5-HT3 receptor sites in the peripheral nervous system (especially in the gut and nociceptive neurons), thereby affecting the regulation of visceral pain, reducing gastrointestinal contractions and peristalsis, and decreasing gastrointestinal secretions. This drug is used to treat diarrhea-predominant irritable bowel syndrome (IBS-D) in women. Alosetron hydrochloride is a small molecule drug, with its clinical trial phase reaching up to Phase IV. It was first approved in 2000 for the treatment of IBS-D. This drug carries a black box warning from the U.S. Food and Drug Administration (FDA). Drugs acting on 5-HT3 receptors alter intestinal motility; agonists accelerate intestinal motility, while antagonists slow it down. All 5-HT3 receptor antagonists can improve symptoms of diarrhea-predominant IBS-D, but constipation is one of its side effects. The order is: alosetron > celansetron > ramosetron > ondansetron. While both alosetron and celansetron are associated with ischemic colitis, there are no reports of ramosetron and ondansetron being associated with it. The principles for using such drugs in IBS-D remain reasonable, as the benefits are sufficient to offset the minor risks of ischemic colitis in patients with severe IBS-D and significantly impaired quality of life, and the symptoms of ischemic colitis resolve rapidly after discontinuation of the drug. The initially recommended dose may be too high, and careful dose titration starting from a very low dose may avoid serious side effects in the future. Preliminary studies have shown that 5-HT3 receptor agonists are beneficial for patients with constipation, but larger-scale studies are needed to determine their risk/benefit ratio. [1]

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Alosetron hydrochloride (Alosetron, GlaxoSmithKline) is a safe and effective drug for some patients with severe irritable bowel syndrome, provided it is taken at the recommended dose. We report the first case of acute liver injury in a 39-year-old white woman who developed symptomatic hepatitis 28 days after starting alosetron. Radiological and laboratory tests ruled out all other possible causes of acute hepatitis, and the liver injury resolved after discontinuation of the drug. Although the mechanism of Alosetron's hepatotoxicity is unclear, it is suspected to be metabolically specific since the drug is known to be primarily metabolized by cytochrome P450 enzymes. Clinicians should be aware of this potential side effect when prescribing Alosetron if patients experience unexplained abdominal pain, jaundice, or abnormal liver function. [4]

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Objective: Alosetron hydrochloride is a potent selective serotonin (3) receptor antagonist that was approved in the United States in February 2000 for the treatment of diarrhea-predominant irritable bowel syndrome (IBS) in women. It was discontinued in November 2000 due to reports of colonic ischemia and severe constipation complications. We aimed to compare the incidence of colonic ischemia, constipation hospitalization complications, and intestinal surgery in a cohort of patients with IBS who were taking Alosetron versus those who were not taking Alosetron. Methods: We analyzed colonic ischemia, constipation-related hospitalization complications, and intestinal surgery outcomes in 3,631 patients taking Alosetron and 2,480 control IBS patients using diagnostic, surgical, and medication information recorded in the UnitedHealthcare claims database. These data were validated through medical record review. The initial assessment plan started with allosetron treatment and lasted for 3 years, enrolling 10,000 patients taking Alosetron; however, due to the drug's discontinuation, the observation period ended on December 31, 2000. Results: Between March and December 2000, 3,631 UnitedHealthcare members were allosetron users, and we simultaneously screened 2,480 control patients with only irritable bowel syndrome (IBS); the mean follow-up time for both groups was approximately 5 months. No colonic ischemia occurred in either group. A total of 30 intestinal surgeries were performed. The surgery rate was 10.2/1000 person-years in the alosetron group and 11.8/1000 person-years in the IBS/non-allosetron group. Three patients were hospitalized due to constipation complications. The incidence rates were essentially the same in alosetron users (1.24/1000 person-years) and in non-allosetron-using IBS patients (0.92/1000 person-years). Conclusion: There was no difference in the incidence of intestinal surgery or constipation-related hospitalization complications between alosetron users and non-allosetron-using IBS patients; no cases of colonic ischemia occurred. The statistical upper limit for the incidence of colonic ischemia in alosetron users is 2.28/1000 person-years. Due to the withdrawal of alosetron from the market, the cohort size and follow-up time were shorter than originally planned; therefore, the conclusions regarding the safety of alosetron are inevitably limited. On June 7, 2002, the U.S. Food and Drug Administration (FDA) re-approved allosetron for the treatment of severe diarrhea-associated irritable bowel syndrome (IBS) in women. [5] Allosetron is a potent and highly selective 5-HT3 receptor antagonist that has been evaluated for the treatment of irritable bowel syndrome (IBS). In vitro studies have shown that allosetron blocks rapid depolarization mediated by 5-HT3 receptors in muscular and submucosal neurons of guinea pig intestines, with a half-maximal inhibitory concentration (IC50) of approximately 55 nmol/L. In awake or anesthetized dogs, allosetron reduces visceral pain caused by rectal distension. It increases colonic compliance with distension in patients with IBS and delays colonic transit in patients with IBS or carcinoid diarrhea, as well as in healthy volunteers. A single dose of 4 mg allosetron increases fluid absorption in the small intestine of normal individuals. In clinical trials of patients with irritable bowel syndrome (IBS), twice-daily administration of 1 mg allosetron effectively relieved abdominal pain and discomfort. Alosetron is most effective in female patients, especially those with diarrhea-predominant IBS. Constipation was the most common adverse reaction in IBS patients and healthy volunteers treated with alosetron. [6] In summary, this study shows that alosetron, as a 5-HT3 receptor antagonist, can reduce the severity of TNBS-induced colitis. Alosetron has a positive effect on colonic injury, neutrophil infiltration and corresponding pro-inflammatory mediators. In addition, the analgesic effect of alosetron on IBS has been well established. Although ischemic colitis is the most serious side effect of alosetron in IBS patients, its incidence is extremely low. In addition, if ischemic colitis occurs during the experiment, we expect the histological and biochemical damage of the colitis to be aggravated. Further research is needed in this regard to determine whether alosetron administration also leads to ischemic colitis in animal models of ulcerative colitis. Based on our findings, alosetron may have a place in the treatment of inflammatory bowel disease (IBD) in the future, but further research is recommended. Conclusion: In summary, although the adverse effect of ischemic colitis induced by alosetron is worrying, it still has anti-inflammatory effects in the TNBS-induced experimental colitis model, and this effect is mediated by 5-HT3 receptors. Therefore, further clinical studies are needed to evaluate its efficacy, safety and applicability in human IBD. [7]

C17H19CLN4O

330.816

330.124

C, 61.72; H, 5.79; Cl, 10.72; N, 16.94; O, 4.84

122852-69-1

Alosetron-d3 hydrochloride;1189919-71-8;Alosetron (Hydrochloride(1:X));132414-02-9;Alosetron;122852-42-0;Alosetron-d3;1190043-13-0;Alosetron ((Z)-2-butenedioate);122852-43-1

60758

Light yellow to yellow solid powder

1.34g/cm3

648.1ºC at 760 mmHg

288-291ºC

345.8ºC

1.1E-16mmHg at 25°C

3.148

2

2

2

23

442

0

CC1=C(N=CN1)CN2CCC3=C(C2=O)C4=CC=CC=C4N3C.Cl

FNYQZOVOVDSGJH-UHFFFAOYSA-N

InChI=1S/C17H18N4O.ClH/c1-11-13(19-10-18-11)9-21-8-7-15-16(17(21)22)12-5-3-4-6-14(12)20(15)2/h3-6,10H,7-9H2,1-2H3,(H,18,19)1H

5-methyl-2-[(5-methyl-1H-imidazol-4-yl)methyl]-3,4-dihydropyrido[4,3-b]indol-1-one;hydrochloride

Alosetron HCl; Lotronex; GR-68755; ALOSETRON HYDROCHLORIDE; 122852-69-1; Alosetron HCl; GR 68755c; Lotrpnex; HSDB 7055; UNII-2F5R1A46YW; GR-68755C; GR68755; GR 68755

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

H2O : ~33.33 mg/mL (~100.75 mM)

Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.

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Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)
*Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution.
Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)
Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil)
Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals).

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Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)]
*Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.
Injection Formulation 5: 2-Hydroxypropyl-β-cyclodextrin : Saline = 50 : 50 (i.e. 500 μL 2-Hydroxypropyl-β-cyclodextrin → 500 μL Saline)
Injection Formulation 6: DMSO : PEG300 : castor oil : Saline = 5 : 10 : 20 : 65 (i.e. 50 μL DMSO → 100 μLPEG300 → 200 μL castor oil → 650 μL Saline)
Injection Formulation 7: Ethanol : Cremophor : Saline = 10： 10 : 80 (i.e. 100 μL Ethanol → 100 μL Cremophor → 800 μL Saline)
Injection Formulation 8: Dissolve in Cremophor/Ethanol (50 : 50), then diluted by Saline
Injection Formulation 9: EtOH : Corn oil = 10 : 90 (i.e. 100 μL EtOH → 900 μL Corn oil)
Injection Formulation 10: EtOH : PEG300：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL EtOH → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline)

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Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium)
Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose
Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals).

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Oral Formulation 3: Dissolved in PEG400
Oral Formulation 4: Suspend in 0.2% Carboxymethyl cellulose
Oral Formulation 5: Dissolve in 0.25% Tween 80 and 0.5% Carboxymethyl cellulose
Oral Formulation 6: Mixing with food powders

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Note: Please be aware that the above formulations are for reference only. InvivoChem strongly recommends customers to read literature methods/protocols carefully before determining which formulation you should use for in vivo studies, as different compounds have different solubility properties and have to be formulated differently.

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 (Please use freshly prepared in vivo formulations for optimal results.)