Is it available on dvd?

Yes, its available as a Region 1 disc (America, Canada) from:

http://www.moviemars.com/i/012569504622_Coma.htm

http://www.playusa.com/DVD/Region_1/3-/97397/-/Product.html?searchstri ng=Coma

If your in Europe or the rest of the world you'll need a region free DVD player in order to play it...

Hope this helps

Brian