Chlorpheniramine and ephedrine in combination for motion sickness.

Background: Chlorpheniramine is effective against motion sickness, but produces sedation. To reduce chlorpheniramine's sedating effect and increase its effectiveness, ephedrine was combined with chlorpheniramine to prevent motion sickness. Methods: Chlorpheniramine (C) and chlorpheniramine plus ephedrine (Chlorphedra) were studied in a randomized, double blind, crossover trial. Eighteen normal subjects were randomized to six different orderings of placebo, C (12 mg) or Chlorphedra (12 mg C + 50 mg ephedrine). They ingested the medication 3.25 hours before off vertical axis rotation in a rotating chair. Cognitive testing with both objective and subjective tests was performed before drug ingestion, at peak drug effect and following rotation. Results: Both C and Chlorphedra significantly increased chair time compared to placebo [6.6 to 10.3 minutes (C), 10.2 minutes (Chlorphedra), p < 0.01]. Subjects reported significantly more sleepiness on the Karolinska sleepiness scale after taking C (3.3 placebo, 4.9 C (p < 0.005)) but not with Chlorphedra (3.3 placebo, 3.1 Chlorphedra). Chlorphedra resulted in significantly higher reported alertness, clearheadedness and attentiveness compared to C. Deficits seen on objective tests with C were corrected with Chlorphedra. Subjects noted more side effects with Chlorphedra. Conclusion: Ephedrine does not increase the effectiveness of chlorpheniramine against motion sickness, but counteracts sedative and performance effects successfully.