The absorption of magnesium dissolved and floating around in water (from a soak), is much much lower than the magnesium concentrated in a cream or lotion. The compounding creams especially are called transdermal gels, and that is because they carry most efficiently of all topical forms, whatever is mixed in them, into the deeper tissues of the skin where most of the blood vessels and capillaries are.

The magnesium cream by Kirkman, has a measuring spoon to deliver 100mg/dose in fact via the cream.

Not everyone gets the same benefit from the epsom soaks.. Alot depends on your skin (males have thicker skin than females), and how long you soak, and how much you dissolved in the bath/tub. But the soaks do work for many, and in varying degrees. I never seemed to get lower blood pressure results from soaks, but I sure do get substantial lowering of my high blood pressure to normal range with the concentrated lotion form of magnesium.

If you do get a transdermal compounded product, I'd ask for magnesium to be in it too... average dose of 100mg/gram (or at whatever dose the pharmacy recommends). Magnesium blocks pain receptors called NMDA receptors, and also opens up little blood vessels to facilitate absorption of the rest of the cream.