Several drug classes continue to be investigated mainly because of their in vitro antiviral activities. Their potential clinical usefulness remains obscure in most instances. Included among these agents are thiosemicarbazones, guanidine, benzimidazoles, arildone, phosphonoacetic acid, rifamycins and other antibiotics, and several natural products.
Oseltamivir is a prodrug that, when hydrolyzed, yields the carboxylated metabolite that inhibits viral neuraminidases of human influenza viruses. Mature influenza viruses bud off from the cell in a sphere of host phospholipid membrane. The virus will adhere to the cell until neuraminidase has been cleaved from the sialic acid residues of the host cell membrane. Neuramidases allow separation and subsequent release of viral progeny. Hydrolysis, or activation, occurs in the GI tract and liver. The use of oseltamivir for treatment of viral diseases in dogs (parvovirus and parainfluenza) is thus far anecdotal.