United States Patent:  6,077,542

Appl. No.:  875597

Substances that are solid at 25^oC. are obtained by dissolving sodium valproate in heated valproic acid and cooling the resultant solution. The resulting solid substances can easily be processed into solid pharmaceutical dosage forms.

SUMMARY OF THE INVENTION

Sodium valproate is somewhat soluble in valproic acid. At room temperature (about 25^oC.) the amount of sodium valproate that can be dissolved in valproic acid is about 50 g sodium valproate per 100 g valproic acid. At this temperature, further quantity of sodium valproate will not dissolve, regardless of blending time. In other words, the saturation point is about 50 g sodium valproate per 100 g valproic acid at about 25^oC.

As the amount of sodium valproate dissolved in valproic acid is increased, the melting point (or freezing point) of the solution also increases. At a concentration of 50 g sodium valproate per 100 g valproic acid, the melting point is still below room temperature, so that a saturated solution consisting of about 50 g sodium valproate per 100 g valproic acid is still a liquid at room temperature.

It has been found that, as temperature is increased above room temperature, the amount of sodium valproate that can be dissolved in valproic acid increases. The melting point of the solution also increases as the ratio of sodium valproate to valproic acid is increased.

The essence of the invention is to heat valproic acid to a temperature substantially above room temperature, to dissolve sodium valproate in the hot valproic acid, the quantity of sodium valproate being substantially above 50 g sodium valproate per 100 g valproic acid, so as to form a solution that has a melting point/freezing point above room temperature and to cool the solution to room temperature, whereupon it solidifies. The result is a substance which is solid at room temperature and is comprised of valproic acid and sodium valproate, the amount of sodium valproate therein being in excess of 50 g sodium valproate per 100 g valproic acid.

The solid substance can then be ground up into solid granules for further processing into solid dosage forms such as tablets.

It will be understood that substances made according to this invention may optionally comprise other ingredients in addition to valproic acid and sodium valproate. That is to say, other ingredients may be incorporated into the hot liquid blend of valproic acid and sodium valproate before it is solidified, and/or other ingredients may be added after the liquid is solidified and ground into granules, by mixing such other ingredients with the granules.

Claim 1 of 8 Claims

1. A process of making a solid substance comprising valproic acid and sodium valproate which process comprises the steps of heating the valproic acid, dissolving sodium valproate therein, and cooling the resultant solution to below the melting point.

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