Why do I feel sleepy and tired after consuming non-drowsy cold/flu-relief medication?
Active Ingredients (in each LiquiCap®) (Purpose)
Acetaminophen 325 mg (Pain reliever/fever reducer)
Dextromethorphan HBr 10 mg (Cough suppressant)
Phenylephrine HCl 5 mg (Nasal decongestant)
It might be that you are sensitive to Dextromethorphan, and that might make you sleepy. If you don't have a cough then you don't need this; choose a product that has only the ingredients you actually need.
The Phenylephine is a stimulant (as well as a decongestant) so it normally tends to counteract the sleep-inducing ingredients, but again each person is different. Sudafed (for example) has just one single ingredient as a decongestant and nothing else.
The Acetaminophen (Tylenol) is normally sleep-neutral for most people; but I find it does make me sleepy, so again, it depends.
And of course you are sick, so that also will make you sleepy.