Enzymes play an important role in pharmacology, allowing the metabolism of drugs. This can be at different stages of the drug’s activity. If a prodrug is administered, enzymes metabolise the prodrug to the active drug form. This is also common with hormones produced by the body, with a prohormone being released that is then modified to become the active form of the hormone. Enzyme inhibitors prevent the catalytic activity from occurring, and so slow or prevent the prodrug from converting to the drug form. For example, grapefruit juice can prevent the metabolism of some prodrugs and lead to a diminished therapeutic effect. Therefore, patient’s taking certain antithrombotic drugs (amongst other classes of drugs) may have to abstain from grapefruits.
Enzymes are also involved in the metabolism of drugs, decreasing the drug’s impact. This can be beneficial, allowing the drug to be excreted. Where this is a very rapid process, inhibitors can be used to slow this, allowing for the therapeutic effect to be extended.