Gamma photon interaction and radiosterilization compatibility of three anticancer drugs: an MCNPX-based assessment with complementary UV photostability screening

Abstract

Gamma photon interaction behaviour of three structurally distinct anticancer drugs (Pemetrexed, Capecitabine, and 6-Mercaptopurine) was computationally characterized using MCNPX Monte Carlo simulation to provide preliminary data relevant to radiosterilization considerations. The effective atomic number (Z_eff), mass attenuation coefficient (μ/ρ), and half-value layer (HVL) were computed across the 0.015–15 MeV range. In the low-energy photon region, 6-Mercaptopurine exhibited the highest gamma interaction potential owing to its high sulfur content, whereas Capecitabine showed the lowest; the interaction parameters of the three compounds converge near the Co-60 sterilization energy range. UV photostability data were examined as a complementary, independent descriptor, reported half lives indicated higher photostability for Capecitabine (t1/2 ≈ 24h) and lower photostability for 6-Mercaptopurine (t1/2 ≈ 5.5h). The two descriptor sets reflect distinct physical mechanisms and are not interpreted as predictive. The proposed MCNPX-based workflow offers a cost-effective computational approach for preliminary radiological characterization of pharmaceutical compounds.