What's Inside: NyQuil, Fortified With Powerful Narcotics!

Acetaminophen
One of the many wonder-pharmaceuticals that can be derived from coal tar, acetaminophen was used for nearly a century as a painkiller and fever reducer before anyone figured out how it worked. We now know that as the drug breaks down in the body, it turns into a cannabinoid: yes, stoners, the same type of compound that makes marijuana so irresistible. Doctors also once thought acetaminophen made users more talkative and outgoing. Current research suggests this idea was half-baked.

Dextromethorphan HBr
A cough suppressant. Well, actually, in the body it becomes dextrorphan, a cough suppressant, and levorphanol, a painkiller five times as powerful as morphine. Like PCP and ketamine, DXM is also an NMDA receptor antagonist, so the National Institute on Drug Abuse lists it as a "dissociative" drug. Twelve times the recommended dose of NyQuil leads to distorted perceptions of sight and sound and produces feelings of detachment — dissociation — from the environment and oneself. For people whose bodies are unusually slow at metabolizing the drug, even low doses of DXM trigger full-blown "Lucy in the Sky With Diamonds" psychedelic trips.

Doxylamine succinate
Officially, this ingredient is on the label as an antihistamine. But it is equally useful as a sleep aid, providing a nice, convenient one-two... Zzzz.

Citric acid
Citric acid has proven somewhat effective as a flu killer, but only if you spray it into your nose. Because NyQuil is meant to be swallowed, not snorted, its presence here is probably to add a little tang, and possibly to act as a low-level preservative.

Alcohol
Hooch has been used as a folk remedy for the common cold for centuries (despite the fact that it doesn't work). But according to Procter & Gamble, alcohol's sole purpose in NyQuil is to serve as a solvent, keeping the top three ingredients in solution.

Polyethylene glycol and propylene glycol
Chemical cousins used as thickeners. NyQuil's consistency is somewhere between water and honey, but not because it needs to be. Drug marketers know many people prefer medicines in syrup form.

Sodium citrate
In other contexts sodium citrate is an anticoagulant; most likely it is used here as a buffer to maintain the acid-base balance of all the other ingredients.

Flavor
P&G isn't talking, but we suspect the cloyingly repulsive taste of NyQuil is to ensure that you can swallow a tablespoon or two but can't drink enough of the stuff to start seeing Jesus.

High fructose corn syrup
A dash of sugar helps that tablespoon or two go down.

Stolen from Here.