Rendering a drug effective or ineffective in a flash at the appropriate location—this is the focus of research in photopharmacology. The goal is to develop drugs that can be switched on and off with light of a specific wavelength. Orally administered medications could then be selectively activated by irradiating only a specific part of the body with light; the medication would remain ineffective in the rest of the body—thus reducing side effects. For example, a drug intended to lower blood pressure in the heart could then be activated only there; other organs with identical binding sites for the active ingredient would remain unaffected.