No middle ground

My husband was diagnosed with ADHD several years into our marriage.  I often feel lonely, ignored and frustrated with his moodiness.  He is either extremely up (child-like, hyper, annoying) or extremely angry and crabby.  There seldom is a middle ground and I find it very difficult to deal with.  I consider myself a very even keel person so it is tough for us to relate at times.  Any advice on how to help him stabilize moods? He is on medication.