Deworming Question??????

Our horse is due for a worming however I don't know his previous working rotation before (We only had him for two months) I tried to get in contact with his old owners but no response I have been trying for several weeks. Anyway I want to start a new worming program with him what brand is best? I heard to start off safeguard 5 day treatment is good is that true? I just don't want him to colic or anything.