Didanosine-d₂is intended for use as an internal standard for the quantification of didanosine by GC- or LC-MS. Didanosine is an antiviral nucleoside analog and an inhibitor of reverse transcriptase.¹It undergoes cellular amination and phosphorylation to its active triphosphate form, 2’,3’-dideoxyadenosine 5’-triphosphate . Didanosine inhibits human T cell leukemia virus type 1 (HTLV-1) reverse transcriptase activity (IC₅₀= 30 nM).²It inhibits the replication of HIV-1 clinical isolates containing various mutations in the gene encoding reverse transcriptase,pol, in isolated human peripheral blood mononuclear cells (PBMCs; IC₅₀s = 0.3-11.1 μM).³Didanosine inhibits proliferation and differentiation of primary human skeletal muscle cells (IC₅₀s = 1 and 0.1 mM, respectively), as well as decreases the activities of mitochondrial complex IV, also known as cytochromecoxidase, and mitochondrial complex II, also known as succinate dehydrogenase, in the same cells when used at a concentration of 1 mM.⁴In vivo, didanosine protects mice from HIV infection (EC₅₀= 13.7 mg/kg).⁵Formulations containing didanosine have been used in the treatment of HIV-1 infections.

1.Perry, C.M., and Noble, S.Didanosine: An updated review of its use in HIV infectionDrugs58(6)1099-1135(1999) 2.Anantharaman, V., and Moen, L.K.Effects of nucleoside analogs on native and site-directed mutants of HTLV type 1 reverse transcriptaseBioorg. Chem.28(5)293-305(2000) 3.Eron, J.J., Chow, Y.-K., Caliendo, A.M., et al.pol Mutations conferring zidovudine and didanosine resistance with different effects in vitro yield multiply resistant human immunodeficiency virus type 1 isolates in vivoAntimicrob. Agents Chemother.37(7)1480-1487(1993) 4.Benbrik, E., Chariot, P., Bonavaud, S., et al.Cellular and mitochondrial toxicity of zidovudine (AZT), didanosine (ddI) and zalcitabine (ddC) on cultured human muscle cellsJ. Neurol. Sci.149(1)19-25(1997) 5.Kaneshima, H., Shih, C.C., Namikawa, R., et al.Human immunodeficiency virus infection of human lymph nodes in the SCID-hu mouseProc. Natl. Acad. Sci. USA88(10)4523-4527(1991)