The psychometric and cardiac effects of dimenhydrinate in the hyperbaric environment.
OBJECTIVE
To examine the psychometric and cardiac effects of dimenhydrinate at 1 and 3 atmospheres (atm) of pressure (0 and 66 feet of sea water, respectively), and to make recommendations about the drug's safety in the diving environment.


METHODS
Double-blind, placebo-controlled, crossover study


METHODS
Monoplace hyperbaric chamber of a university hospital.


METHODS
Thirty active divers (mean age 38 yrs).


METHODS
A bank of seven tests was used to assess cognitive function during four different dive combinations: placebo-1 atm, placebo-3 atm, dimenhydrinate-1 atm, and dimenhydrinate-3 atm.


RESULTS
Heart rate and cardiac rhythm were recorded during all dives. Repeated-measures multivariate analysis of variance was used to analyze the effects of dimenhydrinate, depth, and drug-depth interaction. Dimenhydrinate resulted in a significant decrease in scores of mental flexibility (trail-making, part B, p<0.05) but had no effect on scores in the six other psychometric tests (p>0.05). It had no effect on mean heart rate (p>0.05), although frequent unifocal ventricular ectopic beats occurred in two subjects after ingestion of the drug. Depth resulted in a significant decrease in verbal memory test scores (p=0.001) and mean heart rate (p<0.001).


CONCLUSIONS
Dimenhydrinate adversely affects mental flexibility. This effect, when added to the adverse effect of depth on memory, may contribute to the dangers of diving.
Taylor
D M
DM
Department of Emergency Medicine, University of Pittsburgh, Pennsylvania, USA.
O'Toole
K S
KS
Auble
T E
TE
Ryan
C M
CM
Sherman
D R
DR
D000368:Aged; D000704:Analysis of Variance; D001273:Atmosphere Exposure Chambers; D001274:Atmospheric Pressure; D018592:Cross-Over Studies; D004111:Dimenhydrinate / Q000494:pharmacology*; D004242:Diving / Q000502:physiology*; D004311:Double-Blind Method; D005260:Female; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D006634:Histamine H1 Antagonists / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D008606:Mental Processes / Q000187:drug effects* / Q000502:physiology; D008875:Middle Aged; D011594:Psychometrics; D014145:Trail Making Test / Q000706:statistics & numerical data; D018879:Ventricular Premature Complexes / Q000139:chemically induced
D006634:Histamine H1 Antagonists; D004111:Dimenhydrinate