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Bed Rest Standard Measures: Urea Breath Test (BRSMUBT)
Principal Investigator
Research Area:
Gastrointestinal physiology
Species Studied
Scientific Name: Homo sapiens Species: Human

Gastrointestinal (GI) function plays a critical role in the absorption and bioavailability of orally administered drugs. Further, the GI tract plays a pivotal role in the bioavailability of nutrients. The availability of energy depends on intake, absorption, storage, and utilization. The absorption and bioavailability of ingested compounds depend on physiological factors such as GI motility, splanchnic blood flow, and pH of gastric secretions.

Lactulose (Lac) and acetaminophen (APAP) are commonly used in research and clinical settings to measure gastrointestinal (GI) motility and absorption; similarly, Lac is used to measure GI Transit Time (GITT) and APAP to measure GI absorption as a function of GI motility. These measures are important as they influence absorption and bioavailability of orally administered drugs which in turn influence drug efficacy. These measures are also important because the effectiveness of orally administered drugs is affected by their rate of transit in the GI tract. GI motility has been shown to be slowed in flight and with certain orally administered drugs, astronauts report reduced efficacy and absence of common side effects elicited with the administered dose on the ground. Once validated, GITT and bioavailability measurements using Lac and APAP can serve as standard measures for estimating physiological and functional changes of the GI tract in microgravity and analog environments. These standard measures help understand and estimate risk of failure to treat due to ineffectiveness of medications.

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Gastrointestinal system

Data Information
Data Availability
Archive is complete. Data sets are not publicly available but can be requested.
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Hepatic function
Nutrient absorption
Nutrient balance
Renal function

Mission/Study Information
Mission Launch/Start Date Landing/End Date Duration
Campaign 1 08/29/2004 11/21/2004 84 days
Campaign 3 02/20/2005 04/14/2010 5 years, 1 month, 25 days

Additional Information
Managing NASA Center
Johnson Space Center (JSC)
Responsible NASA Representative
Johnson Space Center LSDA Office
Project Manager: Jessica Keune
Institutional Support
National Aeronautics and Space Administration (NASA)