Deerhounds, like many dogs, can have sensitivities—some severe, or even fatal—to sulfa antibiotics, so it is recommended that these drugs be avoided, if at all possible.
More information can be found here.
More information on the relationship between sulpha antibiotics and folic acid can be found here.
Owners should notify their vets that these drugs shouldn’t be used and make sure that this information is added to their dog’s vet records. If one of these drugs must be used, owners should discuss with their vet supplementing with folic acid while the drug is administered.