Possibly an allergic reaction, most people would tell you to discontinue the antibiotic. No relation to penicillin. Shouldn't be a major problem if in moderation, both can cause gastritis-about the only serious problem. Off hand can't say why, but, if it is repeated, I'd suspect its real. Not a usual problem.
Most hospitals go with the lowest cost alternative to equivalent drugs in a class.
As a consequence, each hospital tends to use either low cost generics or have individual contracts with companies to get the lowest cost. There is no one drug they use, except the most cost effective. I break out in a rash that lasts at least two weeks and itches real bad. Usually where the rash is it will make my glands in that area swell up. Unless you are still taking tetracycline, this is unusual.