Pharmacological interventions for motion sickness: cardiovascular effects.

Motion sickness (MS) was provoked in healthy volunteers subjected to simultaneous rotation through the vertical axis with head movements (HM). Arterial blood pressure (BP), heart rate (HR) and forearm blood flows (BF) were intermittently monitored. Forearm BF was measured by venous occluding plethysmography. Rotation at 20 rpm and cyclic HM were continued for 10 min or until the subject requested cessation of HM because of imminent emesis. There were no consistent changes in BP or HR, but marked increases in BF were observed with MS. There was an inverse correlation between duration of HM tolerance and increments in BF. Antimotion sickness medications scopolamine:d-amphetamine (0.4:5.0 mg) or promethazine:ephedrine (25:60 mg) failed to significantly increase the duration of HM; the latter mixture, however, did significantly reduce the HM-induced-hyperemic responses. Administration of naproxyn (275 or 550 mg) did not significantly alter HM duration or BF responses. These studies suggest that BF changes may be an objective index of MS susceptibility.