Medicinal use of certain tetrazolium salts

A method for inhibiting hard clot formation or supplementing fibrinolytic therapy comprising administering to a patient in need of such treatment an amount of tetrazolium salt effective for inhibiting hard clot formation or supplementing fibrinolytic therapy wherein said tetrazolium salt is represented by the formula ##STR49## wherein Az is a tetrazolium nucleus

• R' and R" indenpendently are lower alkyl from 1 to 5 carbon atoms;
• phenyl;
• substituted phenyl containing from 1 to 3 substituents selected from lower alkyl, lower alkoxy, halo and hydroxy;
• benzyl;
• or phenylethyl;
• R is hydrogen, lower alkyl from 1 to 5 carbon atoms;
• cycloalkyl from 3 to 7 carbon atoms;
• phenyl;
• or substituted phenyl containing from 1 to 3 substituents selected from lower alkyl, lower alkoxy, halo and hydroxy;
• and
• X is a negative radical of a pharmaceutically acceptable acid.