what is analgesics? what is its composition? what is their utility in curing?
I think the title is chemistry.
To answer the first question see
http://www.medterms.com/script/main/art.asp?articlekey=10933
The primary class of analgesics for acute or chronic pain are chemically based on the morphine molecule but have minimal abuse potential. There are other groups as well which have other properties (such as antiimflammatory) as well as relieving pain.
For your last question you might want to look at what is meant by pain and acute and chronic pain.
Hope this helps.