Aza and 6MP figure in the World Health Organization top one hundred list of essential medicines and are prescribed for the treatment of leukemia, autoimmune conditions, and as immunosuppressants. However, research has also shown that UVA irradiation of cells treated with Aza and 6MP causes oxidatively generated damage to both the genome and the proteome. Half of the observed oxidatively generated DNA damage in cells treated with Aza or 6thioguanine (6tGua) has been demonstrated to originate from the direct photoactivation of the metabolized 6tGuo nucleotide in the intracellular pool. Similarly, excitation of 6tGua with UVA radiation has been shown to induce oxidatively generated damage to nucleotides in the intracellular pool, forming the 2'-deoxy-8-oxoguanosine nucleotide, which can then be incorporated into cellular DNA, leading to indirect DNA damage. Therefore, it is important to examine whether Aza and 6MP themselves can induce oxidatively generated damage to cellular DNA in the intracellular pool and to the proteome. To narrow this gap in knowledge, the excited state dynamics and the photochemical properties of the Aza and 6MP prodrugs were investigated in this study to elucidate their electronic relaxation mechanisms, as well as the plausible formation of reactive triplet states and reactive oxygen species in aqueous solutions.