Possible Clues:

• Woman doctor has to pull out — might this prevent misrepresentation?
• Lying low following its administration?
• Prescription for Verity?
• Putting an end to the lies, politician admits treatment hurt one of the runners
• Yank rings Doctor Ruth first for something that will put an end to the lies
• Facts on poison won't help you lying
• Book found by doctor in boat that may provide required information
• Supposed means of preventing lying