OBJECTIVES:
Pharmacologic studies of therapeutic agents used by astronauts during space flight need to be performed to compare drug bioavailability and effectiveness during weightlessness with those characteristics under 1-g conditions. To determine the applicability of noninvasive salivary drug monitoring for pharmacokinetic evaluation of therapeutic agents during space flight, three drugs that are frequently used by crewmembers have been selected for in flight study - acetaminophen, a relatively innocuous, common pain relief medication whose disposition characteristics have been well established, and a scopolamine/dextroamphetamine combination, an operational medication used for the treatment of space motion sickness during missions. The feasibility of such an application for salivary drug monitoring depends upon the distribution of detectable levels of the drug into saliva and the establishment of a consistent saliva/plasma (S/P) ratio over the entire disposition profile of the drug.

Ground-based investigations to establish the S/P ratios of scopolamine have been conducted in normal subjects. Following intravenous and oral administration, scopolamine readily distributes into saliva with consistent S/P ratios over the entire disposition profile. In this investigation, the pharmacokinetics of scopolamine/dextroamphetamine following oral administration to crewmembers before and during space flight were evaluated using salivary concentrations to estimate the disposition parameter changes of anti-motion sickness agents during missions.

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