In one sense there is not much to say about Frank Schleck’s positive drug test (of his A sample only at the time of writing). Xipamide is not likely to enhance performance in its own right; it is banned as it could “mask” the use of other substances that are effective. Xipamide is a diuretic; it makes you urinate more. It therefore has the potential to affect the metabolism of another banned substance. You pee more and so all the drugs in your body are expelled faster.
Xipemide is a drug in current clinical use and so there could be medical reasons for taking it. Hence it does NOT lead to an immediate outright ban with no questions asked. But an athlete does need to explain why it is in his/her body in order to get away with just a slap on the wrists. If Schlek’s B sample does turns out positive it would be nice to know what really happened here. Though I doubt anyone will tell.
I am always somewhat surprised about why these sort of compounds are used. Drug metabolism rates are so individual that it is possible you are just adding to your chances of being caught by taking two banned substances. Were I to be a doper-in-chief I would want to measure the metabolism of both the performance enhancing drug and the masking agent, before deciding whether to risk this. Fortunately this sort of precision is only possible with the connivance of a testing lab. This used to happen in the bad old days of the East German state-sponsored doping; then the while team was pre-tested to ensure that the anabolic steroids they had taken were undetectable prior to competing at the Olympics. But I think it is an unlikely occurrence now.
As for xipamide? It will now return into obscurity. Apart from one footnote: every patient who searches the internet in order to find out about the drug used to treat their fluid retention will now have to wade through a mass of cycling stories at the same time…..