VIABEST-100 Tablets VIABEST-100 contains Sildenafil Citrate, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5). During sexual stimulation, nitric oxide (NO) is released in the corpus cavernosum, activating guanylate cyclase and increasing intracellular levels of cGMP. Sildenafil inhibits PDE5, the enzyme responsible for the degradation of cGMP in the vascular smooth muscle of the penis, thereby facilitating prolonged accumulation of cGMP. Elevated cGMP levels induce smooth muscle relaxation and vasodilation within the penile arteries and erectile tissue, enhancing blood flow to the corpus cavernosum and promoting a natural erectile response. VIABEST-100 is indicated for the treatment of erectile dysfunction (ED) in adult males.