
Magnesium is used as a laxative (milk of magnesia, oral mag sulfate, etc), antacid, but is also a major mineral for muscle contractions, enzyme reactions, and nerve transmission, so any imbalance can cause neurological problems, depending on the severity. And, not having enough can cause neuro problems- depending on the severity.
Mag Sulfate is a standard med given to treat pre-eclampsia (high blood pressure in pregnancy), and some types of seizures-eclampsia (seizures from high blood pressure in pregnancy)- however, lab results would be needed prior to starting anyone not pregnant on magnesium to know where they were starting from. Because of all of the 'real' anticonvulsants, mag sulfate is almost exclusively used for seizures or symptoms of pre-eclampsia/eclampsia in pregnancy.....it would have to be a last ditch option for most types of seizures, unless there were an enzyme/biochemical need for magnesium for that type of seizure- with over 100 types of seizure syndromes, and the biochemical reasons for some, I can't give you the exact types of seizures that would be prime candidates for magnesium- but it's not a general epileptic 'medication' (mineral).
The side effects are known to be VERY lousy (pregnant women go through h*ll during treatment to save their babies with this), and is not an easy med to take at the doses needed to provide anticonvulsant properties....the stuff at the drugstore is weenie doses, and essentially pointless for most people.
SO, it IS an anticonvulsant, but the doses needed excede the tolerance most people would have for the side effects, and, other more specific medications for seizures are available, and more targeted for certain types of seizures. Unless I was pregnant and had life-threatening blood pressure that would likely kill me or my baby, there's no way I'd take it, with the side effects, when there are other meds out there for epilepsy.
Also, it's not available except for IV or injection doses in the amounts needed to stop seizures...
The only oral uses are laxatives and mineral supplements (the weenie drugstore doses)- and if magnesium isn't taken in a ratio with other minerals, it's not absorbed well orally.