Compositions and methods for increasing efficiency of cardiac metabolism

1. A HCl salt of a compound represented by formula (X):

2. The HCl salt of claim 1 , wherein the salt is a monohydrate.

3. A pharmaceutical composition comprising the HCl salt of claim 1 .

4. The pharmaceutical composition of claim 3 , wherein the composition comprises the compound in a therapeutically effective amount to increase cardiac efficiency in a subject.

5. The pharmaceutical composition of claim 3 , wherein the composition is formulated for oral administration.

6. The pharmaceutical composition of claim 5 , wherein the composition comprises a format selected from the group consisting of a tablet, troche, lozenge, aqueous suspension, oily suspension, emulsion, syrup, hard capsule, and soft capsule.