Depends on what's in the medicine you took. Are you on any other medications it could have had a reaction with? Does is contain pseudoephedrine (you had to purchase from the pharmacist with an ID)?
I find medications with the pseudoephedrine give me speed like effects and would definitely stop me from sleeping. I have had reactions between night time cold meds with certain prescription anti-depressants make me feel like I'm on speed.
If it's a night time medicine, usually there is something in the medicine that will make you sleep or drowsy and it all depends on how your body reacts to those things as well. I can't take Nyquil because after 4 hours I'm wide awake.