DMSO may occasionally be used as an IV when treating a severe case of laminitis to help ty to limit the inflammation, however it's not common. You can also apply it topically for local inflammation relief, but this is not very effective for the hoof and it can cause skin reactions in some horses.
Your best bet is to determine if there is an underlying cause for your horse's laminitis risk like Insulin Resistance or Cushings and manage his diet to minimize the risk. As for treating laminitis/founder, immediate treatment at the first sign of symptoms with systemic anti-inflammatories like Bute and Banamine and maintenance with soft footing, correctiving trimming, deitary changes, etc are the best ways to manage the problem.
Has your vet determined exactly why your horse developed laminitis? Have you done more than limit grazing time? What breed is your horse? What are you feeding? Is your horse cresty necked, have fat pads at shoulders or tail head?
I would suggest that you check out the Laminitis webinar that The Horse magazine has available. It's about an hour long and has tons of good info. http://www.thehorse.com/Videos.aspx