generally all your medical files are off limits unless you specifically sign for their release. just keep your mouth shut about past medications and past medical stuff, unless you're going for a job that requires having a security clearance, in which case the best thing to do is be absolutely open and honest about everything they will find on the investigation request stuff you have to fill out as the first part of getting a clearance.
a recruiter should tell you the same thing, dont tell them anything they dont need to know. medications you're currently on, you will probably have to mention. its been a few years since i've read the regs so they're probably updated; as of 2012 bupe maintenance wasnt specifically prohibited but methadone was. some positions with the federal government will reject candidates for being on bupe, so its probably the same for the military (and they will test for it as part of the drug screening, so dont try to lie).
typically the best thing you can do is ask the recruiter for advice, but as long as you dont get rejected at MEPS (where they do the medical processing, physical, drug screening, etc) you should simply be able to fix up whatever might reject you and, at worst, go through a different recruiter.