Yes it can be dangerous and if you're thinking to do so the could be multiple reasons for that including death wish which is rather a serious problem and needs evaluation from experts.

It appears to be a planned act rather than accidental, otherwise you would not have been asking this question here. Self medication is never advisable. There is always a risk of complications and adverse effects, may it be Nipam or anything else. With sleeping pills like Nipam, there is risk of respiratory depression and death. There are innumerable instances of such acts in history. If you are not feeling well, it is in your best interest if you visit a psychiatrist in person who will definitely help you in dealing with whatever bothering you.

Yes it's not advisable to do so.. Do consult for your issue