Has anyone experienced their dog dripping drops of 'water/saliva" from their mouth?  I'm not talking about drooling but just drops of water like a faucet not turned off completely and dripping? 

This isn't the first time he has done this.  I've asked the vet and she didn't know why.  Sometimes it will last for hours and then may not happen again for a week or so.  This happened to my other dog once or twice.  They are both on medications.  I've thought that perhaps a pill was stuck on the roof of his mouth or in his throat but it happens when he hasn't had pills for awhile.