Drug interactions can change how your drug function or increase your chance of experiencing major adverse effects.
Which is why checks as for any drugs need to be made. Every drug may have undesired side effects. That's something many like to forget...
I totally agree on this.
That is why a doctor has to prescribe and not just anybody
There is very right! By the way, there was a recent post on self medication last week (see here) by @eni-ola, that you may actually find interesting. It is totally related to this last comment.