Methods for treating or preventing bacterial or protozoal infections in mammals by administering a single dose of an antibiotic composition comprising a mixture of azalide isomers and a pharmaceutically acceptable vehicle are disclosed. Methods for increasing acute or chronic injection-site toleration in mammals by administering a single dose of antibiotic compositions comprising a mixture of azalide isomers and a pharmaceutically acceptable vehicle are also disclosed. A combination comprising: an antibiotic composition comprising a mixture of azalide isomers, a pharmaceutically acceptable carrier, and instructions for use in a single-dose administration is also disclosed.