Stable levothyroxine compositions in aprotic polar solvents
The present invention concerns the use of aprotic polar solvents and an ionization stabilizing agent to prepare stable therapeutic formulations of levothyroxine by dissolving levothyroxine in an aprotic polar solvent system that can then be used to treat, prevent, and/or diagnose certain diseases and disorders in humans and veterinary animals by administration of the formulation thereto. In certain embodiments, the invention is directed to formulations comprising levothyroxine, and optionally one or more additional therapeutic agents, dissolved in an aprotic polar solvent system, such as a DMSO/water admixture comprising at least one ionization stabilizing excipient in a concentration sufficient to impart physical and chemical stability to the therapeutic agent. The invention also provides methods of use of such formulations in treating, preventing, and/or diagnosing diseases and disorders, and methods of manufacturing such formulations.
1 . A method of treating hypothyroidism in a subject in need thereof, the method comprising introducing into the subject a therapeutically effective amount of a storage stable therapeutic formulation, monitoring levothyroxine levels in the plasma of the subject over time, and repeating the introduction of the therapeutic formulation into the subject as needed to treat hypothyroidism in the subject, wherein the therapeutic formulation comprises:
(a) levothyroxine or a salt thereof, at a concentration of about 10 mg/mL;
(b) an ionization stabilizing excipient, which is sulfuric acid, at a concentration of about 26 mM to about 32 mM;
(c) an aprotic polar solvent, which is dimethyl sulfoxide (DMSO);
(d) a sugar, which is trehalose or a salt or hydrate thereof, at a concentration of about 5.5% (w/v); and
(e) a sugar alcohol, which is mannitol, at a concentration of less than 3.0% (w/v);
wherein the therapeutic formulation is storage stable for at least six months at 2° C.-8° C., and wherein the formulation, when administered to the subject, results in the presence of therapeutic levels of levothyroxine in the blood of the subject for an extended period of time relative to an immediate release formulation comprising levothyroxine.
2 . The method of claim 1 , wherein the levothyroxine or a salt thereof is levothyroxine sodium or levothyroxine free acid.
3 . The method of claim 2 , wherein the levothyroxine or a salt thereof is levothyroxine sodium.
4 . The method of claim 1 , wherein the sugar is trehalose dihydrate.
5 . The method of claim 1 , wherein the therapeutic formulation further comprises a preservative.
6 . The method of claim 5 , wherein the preservative is a benzyl alcohol.
7 . The method of claim 1 , wherein the therapeutic formulation is introduced into the subject via parenteral administration.
8 . The method of claim 7 , wherein the parenteral administration is via injection or infusion.
9 . The method of claim 8 , wherein the injection is a subcutaneous, intradermal, or intramuscular injection.
10 . The method of claim 9 , wherein the injection is a subcutaneous injection.
11 . The method of claim 8 , wherein the infusion is accomplished by pump infusion.
12 . The method of claim 11 , wherein the pump infusion comprises continuous or bolus pump infusion, or a combination thereof.
13 . The method of claim 1 , wherein the hypothyroidism is associated with or characterized by thyroiditis, Hashimoto's Disease, myxedema or myxedema coma/crisis.