Bone Weakness ~ It is a documented fact that dilantin eats calcium (your bones) and with long term use you COULD develope early Ostioperosis.
To overcome this, try taking a calcium supplement such as 500mg calcium with vitamin D (to help the calcium get absorbed into the bones).
I've been on dilantin for 29 years (I'm 52 now) and just recentky had a bone scan and was normal.
Mood Swings ~ Check with your Doctor on this, perhaps a mood stabilizer such as Celexa or Lorazapam.
Blood Levels ~ Keep your blood levels in check or the dilantin can cause unsteadyness and poor co-ordination (this is when the dilantin becomes "TOXIC")
Dental ~ Same as above, calcium and quarterly dental check ups to keep your gums in check.
But most importantly ~ check with your Doctor on all of these and mention your concerns.