Prior to the late Sixties, the vast majority of cold remedies were sold as tablets. Liquids were only reserved for treating coughs. Vicks' Reserch and Development team then formulated a liquid cold remedy that would also help people sleep. As to how NyQuil received its name, no one is quite certain of that. According to the Vicks web site, one legend is that it came from the phrase "nighttime tranquillity." NyQuil was first test marketed in 1966. In the fall of 1968 it was introduced to the general public with a blitz of television commercials and print ads. It was in 1979 that the classic slogan "The nighttime sniffling sneezing coughing aching stuffy head fever so you can rest medicine" was introduced.
Over the years, beyond its packaging, NyQuil would change very little. It was in 1987 that a cherry flavoured version of the medicine was introduced. In 1991 NyQuil LiquiCaps were introduced. Not only was it the first time that NyQuil was sold in something other than a liquid, it was also the first time that a liquid cold remedy was placed within a capsule. Eventually it would lead to nearly every Vicks cold medicine product to be sold in solid form. In 2006 NyQuil Sinus was introduced.
It was also at this time that a significant change was made in the NyQuil formula. NyQuil originally contained the nasal decongestant pseudoephedrine, an ingredient used in making metaaphetamines. In 2006 the Combat Methamphetamine Epidemic Act was passed, seeking to stem the spread of metaaphetamines. According to the new law, all pseudoephedrine-containing medicines would have to be kept behind pharmacy counters and every single purchase recorded. Vicks decided that to keep their products in easy reach of consumers, they would remove pseudoephedrine from all their products. The pseudoephedrine in NyQuil was then replaced with phenylephrine. When many protested that phenylephrine was less effective than pseudoephedrine, Vicks introduced Nyquil-D, essentially the original NyQuil formula. As it contains pseudoephedrin, NyQuil-D is kept behind pharmacy counters.
Here I should perhaps say something about NyQuil's daytime equivalent, DayQuil. Development on DayQuil began even as NyQuil was being test marketed. Although tested under the name DayQuil, it was introduced in 1976 under the name DayCare. Unfortunately, DayCare would not prove to be the success that NyQuil was. It was reintroduced in 1992 under the DayQuil name.
Below is an early advert for NyQuil, I suspect from the late Sixties or early Seventies. Notice the well known slogan is absent.
Below is a 1993 commercial, by which time the well known slogan was in place. By the way, if the actor in the advert seems familiar, it's because it's Nathan Lane.
Finally, here is more recent commercial which aired during the Vancouver Winter Olympics. It stars short track star Apollo Ohno (sadly, they did not make one with Lindsey Vonn, whom I much prefer looking at....).
When NyQuil was introduced in 1968, it was revolutionary. At the time liquid cold medicines were nearly unknown. Since then it has generated many spinoff products, everything from NyQuil Cold/Flu Multisymptom Relief to NyQuil Sinus, LiquiCaps, and even DayQuil. It has also inspired many imitators over the years, products which also seek to treat cold symptoms while providing for a good nights sleep. Arguably, it has been one of the more successful products of the late Twentieth Century.