It is a narcotic pain reliever and addictive. Here's one reference:
Hydrocodone Information from Drugs.com
Hydrocodone and acetaminophen is used to relieve moderate to severe pain. Includes hydrocodone and acetaminophen side effects, interactions, indications

http://www.drugs.com/hydrocodone.html


And do a search for 'hydrocodone side effects'

If you are having chronic pain there may be some other way to get relief without taking this opoid.