Hexamine (methenamine USAN) does not fit into any classification system so it is stuck in here at the end. It is sometimes called a urinary antiseptic. It is a complex amine which is excreted into the urine and broken down in acid urine to formalin, which kills any bacteria present. There is no resistance as such, but bacteria which alkalinise the urine stop the formation of the formalin. Still available in NZ (for people) but not used much (as an antibiotic at any rate - it is used as a fuel for camping stoves and in a wide range of industrial applications).
Triclosan is an old drug traditionally used as an antiseptic mouthwash. It has recently been discovered to act specifically against bacterial fatty acid synthesis and is being reinvestigated. It is effective against most Gram positive and Gram negative bacteria except Pseudomonas. It is also active against some fungi and protozoa. It is being investigated for malaria in man.
Quinoxalines such as carbadox (still used here) and olaquindox (no longer licensed) are mainly G- drugs previously used for growth promotion in pigs, now used to treat scours and prevent swine dysentry. These have been in use since before science was involved in drug licensing and very little is known about them except that they are potentially carcinogenic.
Heavy metals have antibacterial properties. Silver is the only one used therapeutically (usually in combination with sulphadiazine), copper and arsenic are used as growth promoters (qv). Oral colloidal silver was used as an antibacterial before antibiotics were discovered, but is not very effective in any infection. It has recently enjoyed a resurgence of popularity as a “natural” medicine. Overdose can irreversibly turn people's skin a blue gray colour - no information in animals.
