ACtually, drugging in Ireland, while NOT legal, is pretty common - HOWEVER - it tends to be “herbal” stuff with Valerian Root (which, unbeknownst to many, can backfire), tryptothane, B vitamins - and usually for the youngsters. I am sure horses go on Bute, but NOT to the extent they do in the US - (bute costs $2.00 per gram and you HAVE to buy it from your vet!!)
I was astonished by the amount of herbals I saw openly outside horses’ doors at Dublin this year - and, frankly it was v ery depressing. Supposedly, THEY drug test, but the testing and the results are NOT open for public scrutiny. Slap on the wrist is about it.
However, in the FEI classes, they are rigorous - both here and in the rest of Europe. The Irish Young Rider Team (SJ) was suspended for drugging their horses last year during the SJ Europeans (YR)… Baaaadddd coach - who told the kids it was OK and would make their horses go better!!! 
I WOULD rather see herbals than MANY of the US concoctions I have know!!
AND IF you DO buy a horse in Europe, DO get it drug tested - I would even recommend sending the sample to a good US lab for analysis!
It’s OUT! Linda Allen’s 101 Exercises for Jumping co-authored by MOI!!!