Hydroxylation can either activate or deactivate a drug. By adding a hydroxyl group, the lipophilicity of the compound is reduced, generally making it more water-soluble and thus easier to excrete. This process can also produce metabolites that may be more or less active than the parent compound. For example, hydroxylation of codeine results in the formation of morphine, an active metabolite. Conversely, the hydroxylation of certain toxins can lead to the formation of more toxic compounds.
