Prevention of experimental motion sickness by scopolamine absorbed through the skin.

A double-blind placebo-controlled study compared the efficacy of the antimotion sickness drug scopolamine when administered by oral or transdermal routes. A secondary purpose was to extend our bioassay involving fixed-dose combinations of the homergic drugs promethazine and ephedrine. After receiving 12 apparently identical drug-placebo treatments, eight normal male students were exposed to a slow rotation room to stressful accelerations generated by their execution of 40 head movements out of the plane of the room's rotation of 1 rpm and at 1-rpm increments until either symptoms were experienced (just short of frank motion sickness) or the 27-rpm ceiling on the test was reached. Efficacy of a drug was defined in terms of the placeborange and categorized as beneficial, inconsequential, or detrimental. The rank order of drugs with beneficial effects was: 1) promethazine 25 mg plus ephedrine 12.5 mg (86%); 2) scopolamine by mouth (75%); 3) scopolamine transdermally (63%); and 4) promethazine 12.5 mg plus ephedrine 25 mg (29%). The only detrimental effect was with scopolamine given orally. It is concluded that the advantages of the transdermal scopolamine, which include minimal side effects and prolonged effectiveness, deserve full exploitation.