The dose of vetoryl, like most drugs, is dependent on the weight of the animal, so the bigger the animal the higher the dose. That being said some big dogs only need small doses and some little dogs need large doses, it depends on the severity of the disease and the patient. The dose needs to be adjusted until the adrenal glands are appropriately suppressed.
Unlike many drugs which need to be given at the correct dose to be effective, because of the way vetoryl works, lower doses should result in at least a partial response, so a lower dose may be enough to get rid of the worst of the symptoms, or at least make them manageable; the same result might be achieved by dosing every other day. Obviously the correct daily dose is the best way to treat the patient.
As far as starting on a lower dose goes, it is always better to gradually increase the dose to avoid potentially fatal problems associated with high doses, but again the starting dose depends on the size of the dog.
Part of the problem here is that Cushings can have lots of different symptoms - at worst dogs can be diabetic and have a suppressed immune system so they keep getting infections - these cases need to receive the full dose of vetoryl or the dogs will be very ill. Some dogs with Cushings, however, are quite well in themselves and in some cases, especially quite old dogs, treating Cushings may be more detrimental than not doing so, because a lot of dogs with Cushings feel quite good with more steroids whizzing round their system. Obviously each patient needs to be assessed as to what is best.
Another consideration regarding the cost of vetoryl is that the drug mitotane which we used to use was also much more expensive and also more dangerous.