I personally believe that the Epsom Salts play a big part in relaxing the ducts thus making it easier for stones to be expelled. I hate it but I have not wanted to reduce the amount because of the relaxation factor.
An easier way...one or two gulps instead of 3/4 of a cup worth. Dissolve 1 tablespoon of ES in 1/4 cup water instead of 3/4 cup water. Down that 1/4 cup and follow with 1/2 cup of plain water for a total of 3/4 cup liquid each dose. The miserable taste is much more shortlived this way.