How similar is similar enough? The story of the β-blocker metoprolol
What is it about?
Metoprolol is a cardioselective β1-adrenergic blocking agent that shares part of its molecular skeleton with a large number of other β-blockers. Here we present its molecular and crystal structure as compared with that of the closely related betaxolol. Results show that crystal structure similarities do not imply similarities in macroscopic behavior: the two drugs respond differently to temperature stimulus.
Why is it important?
In this paper, the last of a series involving metoprolol & its commercial salts, we tried to rationalize the anisotropic thermal crystal expansion observed in the free base and in some of its salts. The impossibility to definitely find a reason for this behavior, not observed for example in the strictly related betaxolol compound, is a clear remind that although much has been done within the framework of structure–property/function relationships, much remains to be done, especially when APIs are concerned, due to the relevance of their solid-form properties in view of their pharmaceutical development.