I must be one of the long term gout candidates who have been "cured" by 300mg of allopurinol every day.
I was originally diagnosed as having the dreaded condition back in '67 (to the hilarity of my RAF mates who made a great play of helping me into the aircraft!). It came back in '72 and an RAF Medical Specialist put me on the drug that I have taken every day since.
I have now spent thirty years without even a twinge. The only side effects to the drug that I have heard of all seem to be beneficial. The only cautionary note that I would add is to keep your body fluids up, as in later life I have had the odd problem from passing very small Kidney stones. This too is a metabolic problem so they might be related.
It will not prevent you holding a class one medical.
Having had the odd attack of gout does make one realise the unbelievable agony that some people suffer who have untreatable arthritic or rheumatic conditions. I consider myself very lucky to have gout!