Some folks(Kathy Love included) recommend a few things like Grapefruit-seed extract(mixed with water), Nutri Bac which can replentish the small organisms/enzymes in the gut, and certainly last but NOT least, would be Flagyl(Metronidazole) given at a dose of 25-50 mg/per kg animal weight to kill problematic pathogens in the gut. Don't forget, if snakes are allowed to regurge more than a few times without being corrected, it can easily lead to the death of the snake, especially a young one because of the great depletion of acids/enzymes, and electrolyte balances used for digestion.
I personally have used Flagyl before in rare instances with GREAT success. I've had a few snakes in the past that have regurged several meals(no matter how small) and were then administered Flagyl at the higher dose(50mg/kg)(repeat in 14 days), as it is VERY well tollerated by snakes, and instantly STOP! regurging, and hold down EVERY meal from then on.
I would also highly recommend the snake's temp be boosted up to the mid to high 80's, as this will help allow the snake's own metabolism to speed up and help combat the problem. Make ABSOLUTELY SURE you wait approx. a week after administering any of these to attempt another feeding, and then only offer a VERY small meal. Once the snake has held down several smaller meals, you could then increase the size. If any of these DO NOT work, it is time to make a direct path to herp qualified vet, as by this time the problem has been allowed to continue for some time, and the snake would then be in great danger of dying.
hope this info helps you out!...good luck on the snakes speedy recovery!
~Doug
-----
"Better to be silent and thought a fool, than to open mouth and remove any doubt!"