The present invention provides formulation parameters and manufacturing conditions for stable pharmaceutical compositions comprising N-{4-(2,2-dimethyl-propionyl)-(5R)-5-[(2-ethylamino-ethanesulfonylamino)-methyl]-5-phenyl-4,5-dihydro-[1,3,4]thiadiazol-2-yl}-2,2-dimethyl-propionamide that minimize undesirable chiral conversion to the less active S enantiomeric form.