I think that if you know what the purpose is, then it's not "breaking the sobriety." If you were taking something to take the edge off around the house, like maybe I'll fix that window after I've relaxed with this pill, well, that would be different. Plus, if for any reason you thought you had a danger of having more than what helps in the air, then your doctor can make sure you don't have more. If he needs to be told that, well, you can tell him that, just like you are asking the question here, ie, being honest and careful.