From the Merck Vet Manual on Sulfonamides:
http://www.merckvetmanual.com/mvm/index ... 191131.htm
Sulfonamides included in this class are sulfathiazole,
sulfamethazine (sulfadimidine), sulfamerazine, sulfadiazine, sulfapyridine, sulfabromomethazine, sulfaethoxypyridazine, sulfamethoxypyridazine, sulfadimethoxine, and sulfachlorpyridazine.
and:
Standard Use Sulfonamides: In most species, members of this large group are administered 1-4 times/day, depending on the drug, to control systemic infections caused by susceptible bacteria. In some instances, administration of the sulfonamide every second or even third day may be
sufficient to maintain blood levels if the drug is eliminated particularly slowly in the species being treated.