Prokinetic effects of erythromycin after antimotion sickness drugs

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.