This invention relates to a depot formulation comprising a biodegradable silica hydrogel composite incorporating a nucleotide or nucleoside analog reverse transcriptase inhibitor, wherein the silica hydrogel composite is obtainable by mixing silica particles comprising said nucleotide or nucleoside analog reverse transcriptase inhibitor and having a maximum diameter of ≤1 000 μm, as such or as a suspension, with silica sol wherein the hydrogel composite is non-flowing and structurally stable when stored at rest and shear-thinning when shear stress is applied by injection. The present invention also relates to use of the depot formulation for treatment of chronic viral infections and prevention of chronic viral reinfection. The present invention further relates to a prefilled syringes comprising said depot formulation.
