Substitute for Epsom salts?

My 11 year old son has candida and many food allergies and I think he would greatly benefit from a liver flush. I wanted to know if anyone knew of an alternative to Epsom Salts ? I don't feel comfortable giving them to him because I used it for my Liver Flush and experienced many symptoms of hypermagnesemia. I've read magnesium citrate can be used but are there any types of non absorbable forms? Can I used Oxypowder ? He tolerates that very well. Also since he has candida, I was going to have him take malic acid instead of apple juice. Does anyone know what dosage would be suitable? I am kind of nervous about this but nothing else seems to be working and I think he has a serious blockage.