Possible Clues:

• Some commonplace bogus medicine?
• Control, maybe
• Medicine for the mind to settle personal problem
• Medicine which has no physiological effect
• Deliberately inactive drug
• Control group’s treatment
• Lead boxes contaminate oxygen, substance used in clinical trials
• Having unpleasant personal problem on location has no effect
• Location with nasty smell that doesn't affect anybody?
• Opponent originally chasing tie in lead — which has no real effect