In 2010, four out of every five Americans were prescribed antibiotics according the CDC.1 Several of these antibiotics can cause sun sensitivity and require patients to avoid prolonged exposure to the sun. Currently, the FDA’s guidelines for photosafety testing of new drugs relies on using the photochemical properties of the drug, which includes an absorption between 290-700 nm and a molar absorptivity greater than 1000 M-1 cm-1.2 Since these guidelines are quite broad, we are focused on identifying a more specific photochemical property, such as the magnitude of change in dipole moment (△μ) upon absorption, to more accurately predict which potential drugs need to undergo photosafety testing. By finding identifying a more specific photochemical property, we will be able to reduce the number of potential drugs required to undergo photosafety testing and it will enhance our knowledge of the mechanism of these phototoxic reactions. We have chosen to study a commonly prescribed antibiotic, Bactrim®, which is known to induce sun sensitivity, and contains trimethoprim and sulfamethoxazole as the active ingredients. We have measured the stokes shift for trimethoprim from absorption and emission experiments to calculate △μ using the solvent-shift method. Additionally, we have calculated △μ of trimethoprim using Gaussian 09 to compare with experimental results. Future experiments will include calculating △μ for other antibiotics with known sun sensitivity, such as sulfisoxazole, to investigate if there is a correlation between △μ and the side effect of sun sensitivity. By finding a correlation with a more specific photochemical property of photosensitive drugs, this research will aid in understanding the fundamental mechanisms of these phototoxic reactions and may reduce the number of potential drugs undergoing photosafety testing. 1. Hicks, L. A., Taylor Jr., T. H. New Eng. J. of Med., 368, 15 (2013). 2. Photosafety Evaluation of Pharmaceuticals: Guidance for Industry; FDA, CDER, and CBER: Washington, DC, 2015.

Identifying a more specific photochemical property that is responsible for the sun sensitivity side effects observed in commonly prescribed antibiotics

251st National Meeting (2016)

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