|The 2-naphthalenesulfonic acid, 1,2,3,4-tetrahydro-2-methyl-1,4-dioxo-, sodium salt, trihydrate can be prepared by mixing the 2-methyl-1,4- naphthoquinone with the bisulphite salt in the presence of water. Ordinarily gentle warming of the aqueous mixture is preferred to facilitate solution. The mixture of 2-methyl-1,4-naphthoquinone (250 mg; 1 molar equivalent); sodium bisulphite (149 mg; 1 molar equivalent); distilled water (250 ml) or 2- methyl-1,4-naphthoquinone (250 mg; 1 molar equivalent); potassium bisulphate (349 mg; 2 molar equivalent); distilled water 250 ml may be used. These examples representing preferred ratios of ingredients are merely illustrative and are not to be interpreted as limiting.
The bisulphite addition compounds have been found to be stable in sunlight and also to be heat stable. Tests, for example, carried out in ampoules have shown aqueous solutions of the compounds not to be decomposed after exposure to a month's sunlight, while other tests have shown the solutions of such compounds to retain their original potency (a) when stored in an oven at 60°C for 15 days or (b) when sterilized at 15 pounds for 0.5 hour in an autoclave at about 122°C. These properties emphasize the radical differences between the stable salts and the properties of 2-methyl-1,4-naphthoquinone, the characteristic instability of which is illustrated by its sensitivity, i. e., decomposition, when exposed to light.
The bisulphite addition compounds have a vitamin K activity equal to that of the 2-methyl-1,4-naphthoquinone contained in the molecule. The compounds, although suitable for oral administration, are particularly adaptable in aqueous solution for parenteral administration in the treatment of hemorrhagic conditions.