text: The future of photopharmacology holds immense promise. It has the potential to revolutionize conventional drug therapy offering new avenues for precision medicine, treating neurological disorders, and in the field of oncology and ophthalmology.  Additionally, it holds promise for the field of regenerative medicine where photoswitches can be used to modulate the activity of signaling pathways for targeted tissue repair and regeneration.
  Photopharmacology will continue to grow and expand with the new discoveries and advances happening in other related fields such as synthetic chemistry, biology, nanotechnology, pharmacology, and bioengineering. While the potential of photopharmacology is vast, there are some challenges that need to be addressed to make it a clinical reality.  One such challenge is the development of stable and biocompatible photoswitches that are selective for their target receptors without cross-activity. It is particularly important that these photoswitchables have their absorbance bands fall within the wavelength range of 650 nm to 900 nm. Hence, optimum molecular designing of photoswitches is required to achieve the characteristics mentioned above and desired level of performance. At present, photopharmacology uses a rational drug design approach based on studying the structure-activity relationship, however, a phenotypic screening for photoswitchable drugs could also be beneficial. 
  In order to achieve good spatial-temporal control over drug activity there should be a significant difference between the activity of isomers. However, understanding the structural changes during the biological effects induced by photoswitching is limited. This scarcity of knowledge is also a challenge for the growth of this field as it hampers the optimization of the activity and potency of the isomers to obtain the expected outcomes during applications.
  Another hurdle, the biggest challenge in photopharmacology is finding appropriate and effective ways to deliver light to deep tissues in the body and tissues avoiding issues such as scattering and absorption. Various strategies have been attempted in this regard, one being the development of photoswitchable ligands that respond to deep-tissue penetrating wavelengths like red or infrared light. Moreover, some recent preclinical studies have spurred the development of wireless, compact or injectable, and remotely controllable devices capable of delivering light to neural tissues with minimal damage. There are novel optofluidic systems that can simultaneously regulate both drug delivery and light activity at specific sites.  Although, external delivery of light is the most preferred method, the use of internal exogenous light sources such as luminescent compounds where light would be delivered directly at the site of action. This could avoid the issues related to light penetration and also enhance the degree of selectivity. In addition, this creates the opportunity to use photopharmacology as a theranostic approach that combines targeted drug delivery and molecular imaging.