Can I paint exterior paint over interior paint?

No, the exterior paint will not hold up properly indoors or dry correctly. Exterior paint is made differently from interior paint to hold up to weathering. Exterior paint on an interior surface will not work very well, just as interior paint on an exterior surface will not work well over time. The only exception is if the surface you are painting is a door or something like that, that gets exposed to both types of conditions.

http://www.thepaintprofessional.com/

Au contraire, exterior paint will hold up on interior surfaces just fine. The reason NOT to use exterior paint on interiors, is because there is a whole lot more VOC's and bad stuff for peoples health and lungs that would normally get dispersed when used outside. Read the label.

http://www.the-professional-painter.com/