andWhenever damage reduction completely negates the damage from an attack, it also negates most special effects that accompany the attack, such as injury type poison, a monk’s stunning, and injury type disease.
So the DR simply reduces the damage from the normal weapon damage and sneak attack dice, but does not affect the saving throw to avoid death or paralyzation unless the DR also completely negates the damage from the attack.If an assassin studies his victim for 3 rounds and then makes a sneak attack with a melee weapon that successfully deals damage, the sneak attack has the additional effect of possibly either paralyzing or killing the target (assassin’s choice).

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.