Nuclear medicine evaluation of motion sickness and medications on gastric emptying time

Diminished gastric motility and lack of bowel sounds have been observed in astronauts aboard the Space Shuttle (4). In this study subjects were given scopolamine 0.6 mg with d-amphetamine 5 mg with and without neostigmine 15 mg. Neostigmine 15 mg alone was also compared with placebo for effect on gastric emptying time. In an additional test, subjects performed head movements in a rotating chair to an end-point of motion sickness short of vomiting. Ten ounces of isotonic saline containing 1 mCl of Tc 99mDPTA was ingested 2 h after the medications and immediately after rotation. The counts from stomach contents were monitored with a Picker small field of view gamma camera every 30 s for 1 h. Gastric motility was inhibited by scopolamine and amphetamine with 14% residual count at the end of 1 h. When neostigmine was added to this combination the results were in the placebo range. Motion sickness produced a profound inhibition of gastric emptying with a 47% residual count. The results indicate that the gastric stasis encountered in space is due mainly to motion sickness with a minimal contribution from the antimotion sickness drugs.