Motion sickness and the antimotion sickness drugs scopolamine (SCP) and pro
methazine (PMZ) inhibit gastric emptying (GE). This study was conducted to
determine if erythromycin would exert its well-known prokinetic effects in
normal and motion-sick subjects given antimotion sickness drugs. Fifteen fa
sted volunteers (11 males, 4 females) participated in the study. In control
tests, 8 subjects were given intramuscular (IM) saline (SAL, 0.5 ml), SCP
(0.1 mg), or PMZ (25 mg). GE of liquid (300 ml) containing 1 mCi of Tc 99m
diethylenetriaminepentaacetic acid (DTPA) was measured by sequential gastri
c scintigraphy 30 minutes after IM treatments. In other tests, GE was measu
red in 8 subjects after each IM treatment, followed 10 minutes later by 200
mg of erythromycin ethylsuccinate (ESS) suspension given orally In a third
group of tests, 7 subjects received an IM treatment oral EES 10 minutes la
ter, and were then brought to an advanced level of motion sickness short of
vomiting. To induce motion sickness, blindfolded subjects made timed head
movements while seated in a rotating chair. GE was measured immediately aft
er rotation. GE half-life, rate constant, area under the curve (AUC), and l
ag time were calculated using conventional mathematical methods for analyzi
ng exponential rate processes. GE parameters calculated for normal and moti
on-sick subjects given antimotion sickness drugs and EES were compared with
those from subjects given IM treatments (control) only. In normal subjects
, EES significantly (p < 0.05) increased the GE rate constant for all IM tr
eatments and reduced the AUC for SAL, SCP and PMZ by 49% (p < 0.05), 44% (p
< 0.05), and 69% (p < 0.01), respectively In motion-sick subjects, lag tim
e was significantly (p < 0.05) increased, and the rate constant and AUC val
ues were unchanged from control for all IM treatments. The authors conclude
that oral EES reverses the gastrostatic actions of the antimotion sickness
drugs but does not affect the inhibition of gastric emptying associated wi
th motion sickness. The results suggest that motion sickness and antimotion
sickness drugs reduce GE through different mechanisms. Journal of Clinical
Pharmacology, 2000;40:347-353 (C)2000 the American College of Clinical Pha
rmacology.