Note deselected in October 2008, per JSC (4/2009)

NOTE: end date changed to 12/1/2009 per HRP Master Task List information dtd 1/12/2012 (Ed., 1/18/2012)

Midodrine was administered to crewmembers in the manner in which it might be used routinely after space flight. It was administered to five male astronauts 1 hour before landing, near the time of firing the Shuttle main engines to decelerate the Orbiter and begin its descent. The peak therapeutic effect of midodrine occurs approximately 1 hour after ingestion, making it particularly attractive as a landing-day countermeasure, such that its peak effect can be close to the time of the maximum gravitational forces during landing. The purpose of this report is to summarize the preliminary findings from this countermeasure evaluation. The strength of this study is that crewmembers participated in the postflight tilt test of orthostatic tolerance within 60 minutes after wheel stop, and therefore their physical status more closely represented their condition during reentry and immediately upon landing than when testing is conducted in the controlled environment of the baseline data collection facility. Testing in the baseline data collection facility typically occurs about two hours after wheels stop, following the astronauts’ walk-around of the vehicle and subsequent transport to the testing facility.

See also: http://www.nasa.gov/mission_pages/station/research/experiments/Midodrine-SDBI.html

Approximately 90-days before flight, the participants will undergo a drug tolerance test for midodrine and will participate in a drug familiarization session. An operational tilt test will be conducted 10-days prior to launch, and the participants will complete a brief questionnaire before they leave the testing room.

In the course of this study, countermeasure subjects participated in a familiarization session and drug tolerance test, an 80 degree head-up tilt test without medications approximately 10 days before launch (L-10), and the tilt test protocol within 60 minutes of Shuttle landing (R+0). Subjects received verbal and written explanation of all procedures and signed statements of informed consent prior to participation. Preflight Activities

Approximately 10 days before launch (L-10), crewmembers participated in a tilt test in the JSC Cardiovascular Laboratory. Data were collected for 6 minutes while the subjects were supine, before they were tilted to 80 degrees head-up tilt using an automatic tilt table. The subjects remained in this position for 10 minutes, or until symptoms of orthostatic hypotension and/or presyncope occurred.

In-Flight Activities

Crewmembers participated in their scheduled in-flight activities without restriction for the duration of their Shuttle mission. After the decision for deorbit burn was confirmed on the scheduled landing day, crewmembers donned the Advanced Crew Escape Suit (ACES) and ingested 10 mg of midodrine approximately one 1 hour before the scheduled landing time. The midodrine pill and a cue card with medication instructions had been stowed in the subjects’ ACES for their convenience. All crewmembers participated in the standard oral fluid-loading protocol (equivalent to isotonic saline at a rate of 15 ml•kg-1 within 2 hours of landing) and inflated their antigravity suits during reentry and landing.

Postflight Activities

Postflight testing on landing day (R+0) was conducted on the Shuttle runway at either Kennedy Space Center, FL, or Dryden Flight Research Center, CA, in NASA’s Crew Transport Vehicle (CTV), a modified airport “people mover” used to transport the crewmembers from the Space Shuttle to the data collection facility. After Shuttle wheel stop, the CTV approached the Orbiter with the rest of the NASA convoy, and the Shuttle hatch was opened within ~20 min. After a brief medical check by the NASA flight surgeons, the crewmembers exited the Orbiter, with the midodrine test subjects exiting first. The subjects doffed their ACES within 5 min and participated in the same tilt test protocol as during the preflight assessment.

Summary

Midodrine appears to prevent orthostatic intolerance in test subjects after bed rest and in astronauts after space flight when testing is conducted in a controlled laboratory setting within 2 to 4 hours after landing. It is unclear at this time whether similar effects can be expected during reentry and immediately after landing, particularly in warmer environments and/or when the crewmembers are still wearing the ACES. Accurate interpretation of the current data requires that similar data be collected in control subjects (without midodrine) on the CTV. However, concerns about drug interactions with commonly used anti-emetics and prolonged QTc intervals observed in astronauts returning from long-duration missions make the routine use of midodrine unlikely and reliance on lower-body compression garments preferable.

Note deselected in October 2008, per JSC (4/2009)

On Earth, the drug midodrine has been used extensively to treat low blood pressure. . Midodrine acts as a vasopressor (raise blood pressure) by causing constriction (tightening) of the blood vessels which leads to an increase in blood pressure. Test of Midodrine as a Countermeasure Against Post-flight Orthostatic Hypotension - Short Duration Biological Investigation (Midodrine-SDBI) studies the effectiveness of midodrine for the treatment of postflight orthostatic hypotension.

Operational Requirements

Crewmembers will ingest 10 milligrams of midodrine between Time of Ignition (TIG) and landing.

Operational Protocols

Approximately 90-days before flight, the participants will undergo a drug tolerance test for midodrine and will participate in a drug familiarization session. An operational tilt test will be conducted 10-days prior to launch, and the participants will complete a brief questionnaire before they leave the testing room.

See also: http://www.nasa.gov/mission_pages/station/research/experiments/Midodrine-SDBI.html