I don't have a letter, but it should be in my medical notes, and the new psychiatrist will have those. Atomoxetine was never likely to work for me in the first place, but it's the standard first-line drug that the NHS uses for ADHD these days, and from what I can tell, that decision was based entirely on it being a non-addictive non-stimulant, rather than it's medical efficacy, since it has half the rate of success of stimulants in clinical trials, a whole truck load of funky side-effects and costs far more than stimulants. It was originally designed as an anti-depressant, so it's chemical similar to them, but was remarketed as a treatment for ADHD when it failed as an anti-depressant, and given that I've responded very badly to every AD I've tried so far, it didn't bode well for my response to atomoxetine, which turned out to be an extremely vile and horrible drug.
Right now I'm on 20mg a day of dexamphetamine, and the NHS guide says that care must be taken when going from 20mg to a maximum of 30mg, but in the adult clinical trials for dexamphetamine, the doses used were 40-60mg. It doesn't help either that I only get to see a psychiatrist once every few months, and the dose has gone up in 5mg increments on those visits, when it's gone up at all, so it's taken a substantial length of time to get to even this low dose.