Drain mana does no dmg and doesnt break a fear atm. However if u look at patch 3.3.3 changes there is a line: "[Drain Mana]: Drain Mana now clears away any Crowd Control effects such as Hex, Fear, Polymorph, Blind and Seduce.".
Source: http://wowwiki.wikia.com/wiki/Patch_3.3.3
So how it really should be?
Is wowiki a reliable source of that kind of informations?