The main difference is that exterior paint is designed to get wet and take more abuse.  As long as you have a sound surface and a good primer, you can certainly use an exterior paint inside.  The only caution would be if the exterior paint contains a mildewcide.  This shouldn’t be a problem, some bath paints have these too, but if someone had a chemical sensitivity you should be aware.

Answered by Mike Lange, NARI Pro