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| verifiedrevid = 441068590 |
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|ImageFile=tauroselcholic acid.svg |
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| verifiedrevid = 442735848 |
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| ImageFile=tauroselcholic acid.svg |
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|IUPACName=2-<nowiki>seleno]acetyl]amino]ethanesulfonic acid, |
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| IUPACName=(<sup>75</sup>Se)-2-<nowiki>seleno]acetyl]amino]ethanesulfonic acid, |
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|OtherNames=23-Seleno-25-homo-tauro-cholic acid; Selenium homocholic acid taurine; Tauroselcholic acid |
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| OtherNames=23-Seleno-25-homo-tauro-cholic acid; Selenium homocholic acid taurine; Tauroselcholic acid |
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|Section1={{Chembox Identifiers |
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|Section1={{Chembox Identifiers |
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| CASNo=75018-71-2 |
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| CASNo=75018-71-2 |
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| PubChem=123829 |
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| UNII = H6630PU5ZJ |
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| SMILES=C(CCC(NCCS(O)(=O)=O)=O)1()CC2()3()(O)C4()C(O)CC4(C)3()C(O)21C |
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| PubChem = 3086012 |
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| ChemSpiderID = 2342733 |
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| SMILES=C(CCC(NCCS(O)(=O)=O)=O)1()CC2()3()(O)C4()C(O)CC4(C)3()C(O)21C |
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| StdInChI = 1S/C26H45NO7SSe/c1-15(13-36-14-23(31)27-8-9-35(32,33)34)18-4-5-19-24-20(12-22(30)26(18,19)3)25(2)7-6-17(28)10-16(25)11-21(24)29/h15-22,24,28-30H,4-14H2,1-3H3,(H,27,31)(H,32,33,34)/t15-,16+,17-,18-,19+,20+,21-,22+,24+,25+,26-/m1/s1 |
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| StdInChIKey = JCMLWGQJPSGGEI-HZAMXZRMSA-N |
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| C=26|H=45|N=1|O=7|S=1|Se=1 |
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| C=26 | H=45 | N=1 | O=7 | S=1 | Se=1 |
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'''SeHCAT''' is the usual name for 23-seleno-25-homo-tauro-cholic acid (selenium homocholic acid taurine or tauroselcholic acid).<ref>{{cite web|title=23-seleno-25-homotaurocholic acid - Compound Summary|url=http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=700573&viewopt=PubChem|work=CID 123829|publisher=NCBI|accessdate=3 April 2011}}</ref> It is used in a clinical test to diagnose ]. |
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'''SeHCAT''' ('''23-seleno-25-homotaurocholic acid''', '''selenium homocholic acid taurine''', or '''tauroselcholic acid''') is a drug used in a clinical test to diagnose ].<ref>{{cite web|title=23-seleno-25-homotaurocholic acid - Compound Summary|url=https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?sid=700573&viewopt=PubChem|work=CID 123829|publisher=NCBI|accessdate=3 April 2011}}</ref> |
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==Development== |
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==Development== |
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SeHCAT is a taurine-conjugated ] analog which was synthesized for use as a ] to investigate ''in vivo'' the ] of ].<ref name=a>{{cite journal|last=Boyd|first=GS|coauthors=Merrick, MV, Monks, R, Thomas, IL|title=Se-75-labeled bile acid analogs, new radiopharmaceuticals for investigating the enterohepatic circulation.|journal=Journal of Nuclear Medicine|year=1981|volume=22|issue=8|pages=720–5|pmid=7264761}}</ref> By incorporating the gamma-emitter <sup>75</sup>Se into the SeHCAT molecule, the retention in the body or the loss of this compound into the feces could be studied easily using a standard gamma camera, available in most clinical ] departments. |
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SeHCAT is a taurine-conjugated ] ] which was synthesized for use as a ] to investigate ''in vivo'' the ] of ].<ref name=a>{{cite journal|last=Boyd|first=GS |author2=Merrick, MV |author3=Monks, R |author4=Thomas, IL|title=Se-75-labeled bile acid analogs, new radiopharmaceuticals for investigating the enterohepatic circulation.|journal=Journal of Nuclear Medicine|year=1981|volume=22|issue=8|pages=720–5|pmid=7264761}}</ref> By incorporating the gamma-emitter <sup>75</sup>Se into the SeHCAT molecule, the retention in the body or the loss of this compound into the feces could be studied easily using a standard gamma camera, available in most clinical ] departments.{{cn|date=March 2022}} |
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SeHCAT has been shown to be absorbed from the gut and excreted into the bile at the same rate as ], one of the major natural bile acids in humans. It undergoes secretion into the biliary tree, gallbladder and intestine in response to food, and is reabsorbed efficiently in the ileum, with kinetics similar to natural bile acids.<ref name=a/><ref>{{cite journal|last=Jazrawi|first=RP|author2=Ferraris, R |author3=Bridges, C |author4=Northfield, TC |title=Kinetics for the synthetic bile acid 75selenohomocholic acid-taurine in humans: comparison with taurocholate.|journal=Gastroenterology|year=1988|volume=95|issue=1|pages=164–9|doi=10.1016/0016-5085(88)90306-x |pmid=3371611}}</ref> It was soon shown to be the most convenient and accurate method available to assess and measure ] turnover in the intestine.<ref>{{cite journal|last=Thaysen|first=EH|author2=Orholm, M |author3=Arnfred, T |author4=Carl, J |author5=Rødbro, P |title=Assessment of ileal function by abdominal counting of the retention of a gamma emitting bile acid analogue.|journal=Gut|date=October 1982|volume=23|issue=10|pages=862–5|pmid=7117906|doi=10.1136/gut.23.10.862|pmc=1419815}}</ref> SeHCAT testing was commercially developed by Amersham International Ltd (] is now part of ] Medical Diagnostics division) for clinical use to investigate ] in patients with ]. This test has replaced <sup>14</sup>C-labeled glycocholic acid (or taurocholic acid) breath tests and fecal bile acid measurements, which now have no place in the routine clinical investigation of ].{{cn|date=March 2022}} |
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==Procedure== |
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SeHCAT has been shown to be absorbed from the gut and excreted into the bile at the same rate as ], one of the major natural bile acids in humans. It undergoes secretion into the biliary tree, gallbladder and intestine in response to food, and is reabsorbed efficiently in the ileum, with kinetics similar to natural bile acids.<ref name=a/><ref>{{cite journal|last=Jazrawi|first=RP|coauthors=Ferraris, R, Bridges, C, Northfield, TC|title=Kinetics for the synthetic bile acid 75selenohomocholic acid-taurine in humans: comparison with taurocholate.|journal=Gastroenterology|year=1988|volume=95|issue=1|pages=164–9|pmid=3371611}}</ref> It was soon shown to be the most convenient and accurate method available to assess and measure ] turnover in the intestine.<ref>{{cite journal|last=Thaysen|first=EH|coauthors=Orholm, M, Arnfred, T, Carl, J, Rødbro, P|title=Assessment of ileal function by abdominal counting of the retention of a gamma emitting bile acid analogue.|journal=Gut|date=1982 Oct|volume=23|issue=10|pages=862–5|pmid=7117906}}</ref> SeHCAT testing was commercially developed by Amersham International Ltd (] is now part of ] Medical Diagnostics division) for clinical use to investigate ] in patients with ]. This test has replaced <sup>14</sup>C-labeled glycocholic acid (or taurocholic acid) breath tests and fecal bile acid measurements, which now have no place in the routine clinical investigation of ]. |
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A capsule containing radiolabelled <sup>75</sup>SeHCAT (with 370 kBq of Selenium-75 and less than 0.1 mg SeHCAT) is taken orally with water, to ensure passage of the capsule into the gastrointestinal tract. The physical half life of <sup>75</sup>Se is approximately 118 days; activity is adjusted to a standard reference date.{{cn|date=March 2022}} |
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Patients may be given instructions to fast prior to capsule administration; there is significant variation in clinical practice in this regard.<ref>{{cite journal|last=Smith|first=MJ|author2=Perkins, AC|title=A Survey of the clinical use of SeHCAT in the UK.|journal=Nuc. Med. Comms.|date=2013|volume=34|issue=4|pages=306–13|doi=10.1097/MNM.0b013e32835e8989|pmid=23407368|s2cid=28551810 }}</ref> The effective dose of radiation for an adult given 370 kBq of SeHCAT is 0.26 mSv.<ref>SeHCAT. SmPC 2008. GE Healthcare 1-7.</ref> (For comparison, the radiation exposure from an abdominal ] is quoted at 5.3 mSv and annual background exposure in the UK 1-3 mSv.<ref name="pmid17213302">{{cite journal | vauthors = Shrimpton PC, Hillier MC, Lewis MA, Dunn M | title = National survey of doses from CT in the UK: 2003 | journal = The British Journal of Radiology | volume = 79 | issue = 948 | pages = 968–80 | date = December 2006 | pmid = 17213302 | doi = 10.1259/bjr/93277434 }}</ref>) Measurements were originally performed with a whole-body counter but are usually performed now with an uncollimated gamma camera. The patient is scanned supine or prone with anterior and posterior acquisition from head to thigh 1 to 3 hours after taking the capsule. Scanning is repeated after 7 days. Background values are subtracted and care must be taken to avoid external sources of radiation in a nuclear medicine department. |
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==SeHCAT test procedure== |
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A capsule containing radiolabelled <sup>75</sup>SeHCAT (with 370kBq of Selenium-75 and less than 0.1 mg SeHCAT) is taken orally. The physical half life of <sup>75</sup>Se is approximately 118 days; activity is adjusted to a standard reference date. Patients are often fasted before taking the capsule and swallow water to ensure passage of the capsule into the gastrointestinal tract. The effective dose of radiation for an adult given 370kBq of SeHCAT is 0.26mSv.<ref>SeHCAT. SmPC 2008. GE Healthcare 1-7.</ref> (For comparison, the radiation exposure from an abdominal ] is quoted at 5.3mSv and annual background exposure in the UK 1-3mSv.<ref>Shrimpton, P.C; Miller, H.C; Lewis, M.A; Dunn, M. Doses from Computed Tomography (CT) examinations in the UK - 2003 Review</ref>) Measurements were originally performed with a whole body counter but are usually performed now with an uncollimated gamma camera. The patient is scanned supine or prone with anterior and posterior acquisition from head to thigh 1 to 3 hours after taking the capsule. Scanning is repeated after 7 days. Background values are subtracted and care must be taken to avoid external sources of radiation in a nuclear medicine department. |
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From these measurements, the percent retention of SeHCAT at 7 days is calculated. A 7-day SeHCAT retention value greater than 15% is considered to be normal, with values less than 15% signifing excessive bile acid loss, as found in ]. |
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From these measurements, the percent retention of SeHCAT at 7 days is calculated. A 7-day SeHCAT retention value greater than 15% is considered to be normal, with values less than 15% signifying excessive bile acid loss, as found in ]. |
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With more frequent measurements, it is possible to calculate SeHCAT retention whole body half-life; this is not routinely measured in a clinical setting. A half-life of greater than 2.8 days has been quoted as normal.<ref>{{cite journal|last=van Tilburg|first=AJ|coauthors=de Rooij, FW, van den Berg, JW, Kooij, PP, van Blankenstein, M|title=The selenium-75-homocholic acid taurine test reevaluated: combined measurement of fecal selenium-75 activity and 3 alpha-hydroxy bile acids in 211 patients.|journal=Journal of Nuclear Medicine|year=1991|volume=32|issue=6|pages=1219–24|pmid=2045936}}</ref> |
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With more frequent measurements, it is possible to calculate SeHCAT retention whole-body half-life; this is not routinely measured in a clinical setting. A half-life of greater than 2.8 days has been quoted as normal.<ref>{{cite journal|vauthors=van Tilburg AJ, de Rooij FW, van den Berg JW, Kooij PP, van Blankenstein M |title=The selenium-75-homocholic acid taurine test reevaluated: combined measurement of fecal selenium-75 activity and 3 alpha-hydroxy bile acids in 211 patients.|journal=Journal of Nuclear Medicine|year=1991|volume=32|issue=6|pages=1219–24|pmid=2045936}}</ref> |
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==Clinical Use of the SeHCAT test== |
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==Clinical use== |
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The SeHCAT test is used to investigate patients with suspected ], who usually experience ], often passing watery feces 5 to 10 times each day. When ileum has been removed following surgery, or is inflamed in ], the 7-day SeHCAT retention usually is abnormal, and most of these patients will benefit from treatment with ].<ref>{{cite journal|last=Nyhlin|first=H|coauthors=Merrick, MV, Eastwood, MA|title=Bile acid malabsorption in Crohn's disease and indications for its assessment using SeHCAT.|journal=Gut|year=1994|volume=35|issue=1|pages=90–3|pmid=8307458}}</ref><ref name=smith>{{cite journal|last=Smith|first=MJ|coauthors=Cherian, P, Raju, GS, Dawson, BF, Mahon, S, Bardhan, KD|title=Bile acid malabsorption in persistent diarrhoea.|journal=Journal of the Royal College of Physicians of London|year=2000|volume=34|issue=5|pages=448–51|pmid=11077656}}</ref> The ] of bile acids is reduced in these patients with ileal abnormalities and, as the normal bile acid retention exceeds 95%, only a small degree of change is needed. ] can also be secondary to ], ] and other disorders affecting intestinal motility or digestion such as radiation enteritis, ] and ]. |
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The SeHCAT test is used to investigate patients with suspected ], who usually experience ], often passing watery feces 5 to 10 times each day. When ileum has been removed following surgery, or is inflamed in ], the 7-day SeHCAT retention usually is abnormal, and most of these patients will benefit from treatment with ].<ref>{{cite journal|last=Nyhlin|first=H |author2=Merrick, MV |author3=Eastwood, MA|title=Bile acid malabsorption in Crohn's disease and indications for its assessment using SeHCAT.|journal=Gut|year=1994|volume=35|issue=1|pages=90–3|pmid=8307458|doi=10.1136/gut.35.1.90|pmc=1374639}}</ref><ref name=smith>{{cite journal|last=Smith|first=MJ|author2=Cherian, P |author3=Raju, GS |author4=Dawson, BF |author5=Mahon, S |author6=Bardhan, KD |title=Bile acid malabsorption in persistent diarrhoea.|journal=Journal of the Royal College of Physicians of London|year=2000|volume=34|issue=5|pages=448–51|pmid=11077656|pmc=9665518 }}</ref> The ] of bile acids is reduced in these patients with ileal abnormalities and, as the normal bile acid retention exceeds 95%, only a small degree of change is needed. ] can also be secondary to ], ] and other disorders affecting intestinal motility or digestion such as radiation enteritis, ], and ].{{cn|date=March 2022}} |
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A similar picture of ], an abnormal SeHCAT retention and a response to ], in the absence of other disorders of the intestine, is characteristic of idiopathic ] – also called ]. These patients are frequently misdiagnosed as having the ], as clinicians fail to recognize the condition, do not think of performing a SeHCAT test, or do not have it available.<ref>{{cite journal|last=Walters|first=JR|title=Defining primary bile acid diarrhea: making the diagnosis and recognizing the disorder.|journal=Expert review of gastroenterology & hepatology|year=2010|volume=4|issue=5|pages=561–7|pmid=20932141|doi=10.1586/egh.10.54}}</ref> |
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A similar picture of ], an abnormal SeHCAT retention and a response to ], in the absence of other disorders of the intestine, is characteristic of idiopathic ] – also called ]. These patients are frequently misdiagnosed as having the ], as clinicians fail to recognize the condition, do not think of performing a SeHCAT test, or do not have it available.<ref>{{cite journal|last=Walters|first=JR|title=Defining primary bile acid diarrhea: making the diagnosis and recognizing the disorder.|journal=]|year=2010|volume=4|issue=5|pages=561–7|pmid=20932141|doi=10.1586/egh.10.54|s2cid=27123642 }}</ref> |
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There have been at least 18 studies of the use of SeHCAT testing in diarrhea-predominant ] patients. When these data were combined, 32% of 1223 patients had a SeHCAT 7-day retention of less than 10%, and 80% of these reported a response to cholestyramine, a ].<ref>{{cite journal|last=Wedlake|first=L|coauthors=A'Hern, R, Russell, D, Thomas, K, Walters, JR, Andreyev, HJ|title=Systematic review: the prevalence of idiopathic bile acid malabsorption as diagnosed by SeHCAT scanning in patients with diarrhoea-predominant irritable bowel syndrome.|journal=Alimentary pharmacology & therapeutics|year=2009|volume=30|issue=7|pages=707–17|pmid=19570102|doi=10.1111/j.1365-2036.2009.04081.x}}</ref> |
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There have been at least 18 studies of the use of SeHCAT testing in diarrhea-predominant ] patients. When these data were combined, 32% of 1223 patients had a SeHCAT 7-day retention of less than 10%, and 80% of these reported a response to cholestyramine, a ].<ref>{{cite journal|last=Wedlake|first=L|author2=A'Hern, R |author3=Russell, D |author4=Thomas, K |author5=Walters, JR |author6=Andreyev, HJ |title=Systematic review: the prevalence of idiopathic bile acid malabsorption as diagnosed by SeHCAT scanning in patients with diarrhoea-predominant irritable bowel syndrome.|journal=Alimentary Pharmacology & Therapeutics|year=2009|volume=30|issue=7|pages=707–17|pmid=19570102|doi=10.1111/j.1365-2036.2009.04081.x|doi-access=free}}</ref> |
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==References== |
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==References== |
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==External links== |
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