Antibiotics are drugs prescribed to patients who have a bacterial infection to help stop the infection. Just like any drug, the use of antibiotics may result in side effects. While most side effects are generally headache, vomiting, and fatigue- some antibiotics may cause photosensitive reactions on the skin of the patient. These reactions include rashes, dermatitis, sores, and hyperpigmentation. Currently, predicting the photosensitivity of new drugs is difficult, with the only molecular predictors being absorption in the UVA and UVB regions and a molar absorptivity greater than 20,000 M<sup>-1</sup>cm<sup>-1</sup>. Due to the broad nature of these molecular predictors, many drugs meeting these predictors are tested for photosensitivity in clinical trials, only to be found that they do not induce photosensitivity. Our group set out to determine a more specific molecular predictor to increase successful prediction of photosensitive drugs. We will use trimethoprim (a component in Bactrim known to induce photosensitivity) as a model system to correlate specific molecular properties, such as the change in dipole moment upon absorption, to photosensitivity of this drug. Absorption and emission spectra were obtained of trimethoprim in several different solvents to correlate the stokes shift to the solvent polarity in order to calculate the change in dipole moment. If we can correlate the magnitude of change in dipole moment required to induce photosensitivity, this would be a more specific molecular predictor that could be used to screen new drugs for photosensitivity.

Predicting the photosensitivity of photosensitive drugs

251st National Meeting (2016)

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