Colchicine is used for both prophylaxis treatment(preventative) and as an acute attack treatment when you feel a gout attack coming.
Generally speaking, it is administered when starting new uric acid controlling medication such as allopurinol or febuxostat AND when increasing your dose of allopurinol or febuxostat (if required) to prevent attacks whilst those medications begin working and dissolving uric acid crystals or tophi.
It is also taken on the first feeling that a gout attack is about to begin to stop the spread of inflammation and to minimize the length of the attack.
The dosages should be set by your rheumatologist when prescribing it to you. There are generic dosages that you can use but I would recommend you don’t follow them as colchicine can be toxic if administered incorrectly
Take a look at Acute Gout Attack Treatment Plan for a little information.
It is best to seek rheumatologist advice before taking any colchicine.