Carbidopa

Example 3

A 6% Carbidopa solution/formulation was prepared as follows:

Carbidopa [Teva] and L-arginine [Merck] (molar ratio 1:1.1) were weighed in a suitable container and water was then added to obtain 84% of the total projected batch weight. N-methyl 2-pyrrolidone [Pharmasolve, ISP] was added to obtain the final concentration of 5% (w/w) Sodium bisulfite [Sigma] solution was prepared and added to obtain a final concentration of 0.1% (v/w). The mixture was heated to 65±10° C. with constant stirring. When the solids were completely dissolved heating was stopped and the preparation was allowed to cool down to room temperature. Solution was filtered using a sterile 0.22 μM PVDF membrane.

Example 4

A 4% Carbidopa solution/formulation was prepared as follows:

Carbidopa [Teva] and L-arginine [Merck] (molar ratio 1:1.1) were weighed in a suitable container and water was added to obtain 89% of the total projected batch weight. N-methyl 2-pyrrolidone [Pharmasolve, ISP] was added to obtain the final concentration of 3.5% (w/w). Sodium bisulfite [Sigma] solution was prepared and added to obtain a final concentration of 0.05% (v/w). The mixture was heated to 65±10° C. with constant stirring. When the solids were completely dissolved, heating was stopped and the preparation was allowed to cool down to room temperature. The solution was filtered using a sterile 0.22 μM PVDF membrane.

Carbidopa-Arginine solutions/formulations, 2 and 3%, were prepared by diluting the 4% Carbidopa-arginine solution/formulation with respective amount of double distilled water (DDW) containing 3.5% N-MP, with or without 0.05% Sodium bisulfite.

Example 5

An 8% Carbidopa formulation was prepared as follows:

Carbidopa [Teva] and L-arginine [Merck] (molar ratio 1:1) were weighed in a suitable container and propylene glycol [Merck] was added to obtain 75% of the total projected batch weight. Sodium bisulfite [Sigma] solution was prepared and added to obtain a final concentration of 0.05%. The mixture was heated to 65±10° C. with constant stirring. When the solids were completely dissolved heating was stopped and the preparation was allowed to cool down to room temperature. PEG-400 [Merck], 10% of the total projected batch weight, was added. The pH was adjusted to 7.5 with 85% lactic acid [Fluka].