The before and after travel questionnaires wereexamined to identify concomitant medication, includingthat begun during air travel (table 3). Only twopassengers took drugs in addition to their usualmedication. Most drugs were evenly distributed in thetwo groups, although there was a trend towards morepatients taking hormone replacement therapy in thestocking than in the non-stocking group (percentagedifference 8%,CI "1 to 17%). Several volunteers tookaspirin as part of their regular medication.