i agree re the laxative effect of magnesium oxide (and citrate). inexpensive and effective.
ms patients need to absorb their magnesium since levels are typically lower, with a long list of associated symptoms and signs.
in some cases though, such as constipation, the less absorbable, less soluble forms (like oxide and citrate) are beneficial largely for the fact that they go right through you.
the bloating you describe in addition to the constipation makes me also consider zinc as a potential issue. zinc is also low in ms patients and is implicated in a variety of different issues experienced by ms patients.
glad you have something that works for the present at least, since it's a serious problem.
if you decide to introduce magnesium oxide as a laxative, i would hesitate to dump in 1000mg in one go. if you did do that, i'd recommend staying within 5 seconds commute of a toilet throughout that day, with easy fastenings on your pants at that.
you could consider taking 100mg elemental magnesium (from oxide - the pill will have to be a few more mgs to deliver 100mg elemental mag) with each meal for day 1 and day 2, plus an additional 100mg at bed time.
on day three if you have seen no benefit, then you could try 200mg with each meal and at bed time.
if you decide to supplement zinc, it will work best if you reduce or eliminate gluten, sugar, and alcohol intakes. ensure that you take a product that is balanced with copper, since the copper-zinc balance is critical in human health, and excessive zinc supplementation can cause a copper deficit. for example, see if you can find 50mg zinc combined with 2m copper and you should be good.
i too am curious about your diet and activity levels given a 13 year history with ms. iima, what do a typical day's meals and activities look like?
fyi problems associated with poor zinc and magnesium status are diverse - they're involved in 100+ and 300+ pathways in your body, respectively.
in general as a pwms it's wise to boost food intakes of magnesium- and zinc-rich foods, while at the same time reducing intakes of things that impair absorption and/or utilization. food and beverage combinations can have a serious impact on your ability to absorb both zinc and magnesium. i've attached a link below which is pretty bang on, although clearly not specific to patients with ms: http://www.ehow.com/about_6306240_magne ... iency.html
PS if bloodwork for zinc and magnesium levels are feasible, and you're interested, just say the word and i can point you at healthy target levels (a specific place within the so-called 'normal' range)
hope you feel better soon!