Premix of crystalline raltegravir potassium salt and a process for the preparation thereof

1. A process for preparing a premix of raltegravir potassium form 3, the process comprising the steps of:

(a) dissolving raltegravir free base in an ester solvent to create a solution;

(b) adding a potassium source to the solution;

(c) adding a pharmaceutical excipient to form a reaction mass;

(d) cooling the reaction mass; and

(e) isolating the raltegravir potassium form 3 premix from the reaction mass, the raltegravir potassium form 3 premix comprising raltegravir potassium form 3 and the pharmaceutical excipient, wherein the pharmaceutical excipient is at least one of microcrystalline cellulose, polysorbate, mannitol, or hydroxypropyl methylcellulose.

2. The process according to claim 1 , wherein the ester solvent is selected from the group consisting of ethyl acetate, n-butyl acetate, n-propyl acetate, t-butyl acetate, isopropyl acetate, and combination thereof.

3. The process according to claim 1 , wherein the potassium source an alcoholic potassium hydroxide or aqueous potassium hydroxide.

4. The process according to claim 3 , wherein the alcoholic potassium hydroxide is selected from the group consisting of methanolic potassium hydroxide or ethanolic potassium hydroxide.

5. The process according to claim 1 , further comprising adding a second pharmaceutical excipient in step (c).

6. The process according to claim 5 , wherein the pharmaceutical excipient and the second pharmaceutical excipient are selected from the group consisting of microcrystalline cellulose, polysorbate, mannitol, and hydroxypropyl methylcellulose.

7. The process according to claim 1 , wherein the cooling step includes cooling the reaction mass to a temperature between about −5° C. and about 10° C.

8. The process according to claim 1 , wherein said isolating step comprises filtering the reaction mass.