Why do opiates make you constipated? How addicting are they?

I've been taking oxycontin for a while for pain associated with a surgery and I noticed that even after a relatively low dose of oxycontin, I got severely constpiated lol.

Why do they do that? Is that dangerous, or do they somehow do something to the liquids in your body?

I also have dry mouth and I get somewhat hungry, much like smoking pot.

What are side effects of opiate based drugs,

are they dangerous and

how exactly addicting are they?

: http://alcoholdrugstreatment.info/why-do-opiates-make-you-constipated-how-addicting-are-they