Magnesium in oxide form is a laxative. It remains in the bowel and acts as a saline cathartic.

I use SlowMag, mostly because I am sensitive to GI upsets, and some magnesium products loosen me. SlowMag is a long acting form of Magnesium chloride. I have a congenital GI defect, that makes for fast transit, and have to watch what I eat carefully.

But for people on opiate pain therapy, looseness is not an issue for the most part.

I also like Ionic Fizz, which is magnesium carbonate, and goes into solution when you mix it, and has a faster onset.

I buy the generic form of SlowMag for about $5 a bottle at Costco pharmacy. The brand name is $9.99 at WalMart.

Starting at 2 a day, is about 1/2 the RDA.

PeterB at headache here is currently posting with his success with magnesium oil. He takes his orally I believe, but most of the manufacturers of it recommend application to the skin for transdermal absorption.

There have been studies showing Americans very deficient in magnesium. Up to 70% do not get the RDA of it.

Magnesium is used by the body in about 300 different biochemical systems including bone, heart, and muscle functions. Magnesium is a cofactor in the metabolism of Omega-3 essential fatty acids.
This "oil form" is similar to using epsom salts soaks.

Most magnesium products contain oxide, since it is so cheap and historically believed to be useful...(It is not useful as studies have shown for oral supplementation. It is now in Phillips oral tablets laxative)

You may find in stores, magnesium glycinate, citrate, SlowMag, Ionic Fizz, Calm, etc. If you read my magnesium thread on the Vitamin forum, you will see how to choose a supplement, and understand the difference between elemental and final weight dosing.

Magnesium is found in nuts (almonds especially), beans, figs, green leafy veggies. If one eats carefully, one does not need a supplement. This website:
www.nutritiondata.com
gives the nutritional content of most foods and is a good resource!

I think you will find some online magnesium oils, to be more expensive per dose than some other forms.

I tend to want to save money and get quality too, so I share my opinions that way. Magnesium oil seems useful for those who get diarrhea easily from oral supplements. Other than that, it is not much different from less expensive epsom salt soaks.