Is it ok to drink cold medicine with soft drinks???

When I was about to sleep yesterday, I checked on Tattsun's diary translation on livejournal.
And I found an interesting thing on his post in August 25th where he stated that he was sick and decided to got his cold medicine...

And drink nothing but soft drinks...

When I read the post, I suddenly reminded with my cousin's weird behaviour where he always took aspirins with coke...and beer sometimes.

My parents once told me it was dangerous to consume medicine and get some sodas in the range of 12 hours after drank it. They told me it could be dangerous for your heart.

Well, Idk about the real of that whether it's only myth or really-really right.
But me personally don't think it's a good thing as well...
*sighs*
I wish could tell him about this personally LOL
Too bad he can't speak english fluently.

Anybody could tell me about the truth for it?
I mean, it will be helpful not only for Tattsun, but also for every reader here who read it~

Thank you for reading this post (and commenting, if there were some)

I'll make sure to review Diabolik Lover: More Blood Vol. 05 for the next post~
(^~^)/