Prevention of molecular weight reduction of the polymer, impurity formation and gelling in polymer compositions
Polymer and drug containing compositions and method of preparing such compositions are disclosed. The dispersed phase formulation has a polymer, a pharmaceutically or biologically active agent and a small fraction of low pKa acid additive. Stable, filter sterilizable, non-gelling solutions containing GnRH analogs at least at levels typically used in sustained release formulations and a method of increasing solubility of a high level of a GnRH analog or a freeze-dried antgonist of GnRH in a polymer containing solution are also disclosed. The amount of the acid additive in the polymer solution is such that it is sufficient to increase the solubility of the high level of the GnRH analog in the polymer solution without affecting the release characteristics of the microspheres prepared therefrom.
1. A method of increasing the solubility of a GnRH analogue in a polymer containing dispersed phase, the method comprising:
providing a first organic solvent;
dispensing an amount of the GnRH analogue in the first organic solvent to form a first organic mixture such that the GnRH analogue is no longer soluble in the first organic solvent or, even if soluble, the resulting solution gels due to the amount of the GnRH analogue, wherein the GnRH analogue is an agonist or a freeze dried antagonist of GnRH;
dissolving an amount of a polymer in a second organic solvent to form a second organic mixture, wherein the polymer is selected from the group consisting of: poly(d,l-lactic acid), poly(l-lactic acid), poly(glycolic acid), a copolymer of poly(d,l-lactic acid) or poly(l-lactic acid) and poly(glycolic acid), polycaprolactone, copolymer of caprolactone with lactide and glycolide, copolymer of lactide and glycolide with polyethylene glycol, poly(d,l-lactic) acid with polyethylene glycol, or polyanhydride and wherein the polymer has an acid number of about 0.5 to about 50;
mixing the first and second organic mixtures to form the dispersed phase, and
adding an amount of an acid additive consisting of one or more low pKa acids to the dispersed phase, wherein the amount of acid additive in the dispersed phase is sufficient to increase the solubility of the high level of the GnRH analogue in the dispersed phase without affecting the solute release characteristics of any solute bearing microspheres prepared therefrom.
2. The method of claim 1 , wherein the GnRH analogue is the freeze-dried antagonist of GnRH.
3. The method of claim 2 , wherein the freeze-dried antagonist of GnRH is lyophilized from a solution comprising a non-aqueous solvent.
4. The method of claim 3 , wherein said non-aqueous solvent is tert-butyl alcohol or cyclohexane.
5. The method of claim 2 , further comprising heating the dispersed phase to 40 C.
6. The method of claim 1 , wherein the GnRH analogue is orntide, antide, cetrorelix, ganirelix, abarelix, leuprolide, nafarelin, triptorelin, goserelin, busereline, or azaline.
7. The method of claim 1 , wherein the GnRH analogue is leuprolide.
8. The method of claim 1 , wherein the acid additive is lactic acid, glycolic acid, glacial acetic acid, glyceric acid, benzoic acid, propanoic acid, or a combination of these acids.
9. The method of claim 1 , wherein the acid additive is glacial acetic acid.
10. The method of claim 1 , wherein the GnRH analogue is leuprolide, and wherein the acid additive is acetic acid.
11. The method of claim 10 , wherein the second organic solvent is dichloromethane (DCM).
12. The method of claim 1 , wherein the GnRH analogue is leuprolide, wherein the acid additive is acetic acid, wherein the first organic solvent is methanol, and wherein the second organic solvent is DCM.
13. The method of claim 1 , wherein the polymer is poly(d,l-lactic acid), poly(l-lactic acid) or poly(glycolic acid), or a copolymer of poly(d,l-lactic acid) or poly(l-lactic acid) and poly(glycolic acid).