How come librium doesn't work like valium?

A little different: It depends on the effect you're looking for. Librium and valium are both fairly long-acting benzodiazepines, but valium may be a little more potent as an anxiolytic. Valium may also be more lipid soluble, getting into the brain more quickly than librium. Librium's effect may be delayed also because the parent compound is less potent than its metabolites.