FDA: Procter & Gamble Unlawfully Marketing Two Vicks Cold and Flu Medicines Containing Vitamin C (U. S. Food and Drug Administration) The U.S. Food and Drug Administration today sent a warning letter to Procter & Gamble notifying the company that its Vicks DayQuil Plus Vitamin C and Vicks Nyquil Plus Vitamin C are illegally marketed combinations of drug ingredients and a dietary ingredient. [News Source]