which are within the scope of sound medical judgement suitable for use in contact with the tissues of patients without undue toxicity irritation allergic response and the like commensurate with a reasonable benefit risk ratio and effective for their intended use as well as the zwitterionic forms where possible of the compounds of the invention the term u201c salts u201d refers to the relatively nontoxic inorganic and organic acid addition salts of compounds of the present invention these salts can be prepared in situ during the final isolation and purification of the compounds or by separately reacting the purified compound in its free base form with a suitable organic or inorganic acid and isolating the salt thus formed representative salts include the hydrobromide hydrochloride sulfate bisulfate nitrate acetate oxalate valerate oleate palmitate stearate laurate borate benzoate lactate phosphate tosylate citrate maleate fumarate succinate tartrate naphthylate mesylate glucoheptonate lactiobionate and laurylsulphonate salts and the like these may include cations based on the alkali and alkaline earth metals such as sodium lithium potassium calcium magnesium and the like as well as nontoxic ammonium quaternary ammonium and amine cations including but not limited to ammonium tetramethylammonium tetraethylammonium methylamine dimethylamine trimethylamine triethylamine ethylamine and the like see for example berge s m et al pharmaceutical salts j pharm sci 1977 66 1 19 which is incorporated herein by reference examples of pharmaceutically acceptable nontoxic amides of the compounds of this invention include amides derived from ammonia primary c 1 c 6 alkyl amines and secondary c 1 c 6 dialkyl amines wherein the alkyl groups are straight or branched chain in the case of secondary amines the amine may also be in the form of a 5 or 6 membered heterocycle containing one.