The U.S. Food and Drug Administration 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.

Both of the over-the-counter (OTC) medicines, which contain vitamin C in addition to several drug ingredients, are marketed as treatments for cold and flu symptoms. The FDA took the action against the Cincinnati-based company:

To clarify that these single dosage form combinations of drug ingredients and dietary ingredients legally cannot be marketed because they have not been proven safe and effective, and Because the agency previously determined that there are insufficient data to show that vitamin C is safe and effective in preventing or treating the common cold.