Pharmaceutical compositions that have excellent storage stability even though they include a active component that is susceptible to degradation in an acidic environment are disclosed. The stabilized pharmaceutical composition of the invention includes a ring-opened 7-substituted-3,5-dihydroxyheptanoic or a ring-opened 7-substituted-3,5-dihydroxyheptenoic acid, or a pharmaceutically acceptable salt thereof, as an active component and a stabilizing effective amount of at least one amido-group containing polymeric compound or at least one amino-group containing polymeric compound, or combination thereof; wherein the stabilized pharmaceutical composition does not contain a stabilizing effective amount of another stabilizer or a combination of other stabilizers. The pharmaceutical composition may optionally include one or more pharmaceutically acceptable excipients such as a filler, a disintegrating agent and one or more lubricants such as magnesium stearate to aid compression where a tablet dosage form is desired.