My 8 y.o. son has been taking lithium for about a year. It did not completely stabilize his mood, but gave us a step in the right direction. It significantly lessened the amount of mania we saw, but did not eliminate it. We added an atypical AP a few months after lithium.
Talk to the psychiatrist about a schedule for checking your son's lithium levels and thyroid function. We checked my son's lithium levels a week after he started lithium and then two weeks after that. Now we go every 4-6 weeks. At his last check, his TSH (thyroid) level was borderline high, so we are keeping an eye on that. If it goes higher, we will treat that with medication, rather than giving up lithium.
Make sure that your son stays well-hydrated and that he always has access to a bathroom. My son also is in an EBD room and he is exempt from any limitations on the number of bathroom or water fountain trips allowed because the lithium makes him very thirsty (and leads to frequent bathroom trips).
I, too, am surprised your psychiatrist is adding lithium after several medications that can be very activating. Most psychiatrists would take away potentially activating medications to get a baseline BEFORE adding a mood stabilizer.
Good luck.
