title: Space motion sickness countermeasures: a pharmacological double-blind, placebo-controlled study.
abstract: BACKGROUND
  Space motion sickness (SMS), caused by a canal-otolith conflict, is currently treated with intramuscular promethazine. However, the drug has an inconsistent efficacy against SMS. We hypothesize that pharmacological depression of the semicircular canals (SCC) might relieve SMS. The aim of the present study was to identify the effects of meclizine (25 mg), dimenhydrinate (40 mg) combined with cinnarizine (25 mg), and promethazine (25 mg) combined with d-amphetamine (10 mg) on the SCCs and the otoliths.
  
  
  METHODS
  This double-blind, placebo-controlled study was performed on 20 healthy men. Function of the SCC was evaluated by means of an electronystagmography, whereas utricular function was assessed by a unilateral centrifugation test. A cervical vestibular evoked myogenic potentials test evaluated saccular function.
  
  
  RESULTS
  Meclizine (0.54 +/- 0.05 vs. 0.38 +/- 0.06) and dimenhydrinate with cinnarizine (0.54 +/- 0.05 vs. 0.45 +/- 0.05) decreased the vestibulo-ocular reflex gain. Promethazine with d-amphetamine decreased the latency of the saccadic eye response (right eye: 185 +/- 3.8 ms vs. 165 +/- 4.5 ms; left eye: 181 +/- 4.9 ms vs. 165 +/- 4.8 ms) and also increased the phase of ocular counterrolling measured during unilateral centrifugation (0.32 +/- 0.35 degrees vs. 1.5 +/- 0.45 degrees).
  
  
  CONCLUSIONS
  It is hypothesized that meclizine and dimenhydrinate with cinnarizine affect the medial vestibular nucleus. Promethazine is a vestibular suppressor, but study results show that d-amphetamine counterbalances this depression and abolishes the effect of fatigue on the saccadic reaction time The hypothesis that a SCC-suppression alleviates SMS should be further evaluated.
authors.forename: Aurélie P
authors.initials: AP
authors.lastname: Weerts
authors.forename: Robby
authors.initials: R
authors.lastname: Vanspauwen
authors.forename: Erik
authors.initials: E
authors.lastname: Fransen
authors.forename: Philippe G
authors.initials: PG
authors.lastname: Jorens
authors.forename: Paul H
authors.initials: PH
authors.lastname: Van de Heyning
authors.forename: Floris L
authors.initials: FL
authors.lastname: Wuyts
mesh_terms: D000328:Adult; D000932:Antiemetics / Q000627:therapeutic use*; D004311:Double-Blind Method; D064368:Healthy Volunteers; D006634:Histamine H1 Antagonists / Q000627:therapeutic use*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018489:Space Motion Sickness / Q000188:drug therapy*; D055815:Young Adult
chemical_list: D000932:Antiemetics; D006634:Histamine H1 Antagonists