Sildigra 250mg's primary active ingredient is sildenafil citrate, a potent phosphodiesterase type 5 (PDE5) inhibitor. PDE5 is an enzyme that plays a vital role in regulating blood flow in the penis. When there is an excess of PDE5, it can constrict blood vessels in the penile region, making it difficult to achieve and maintain an erection. Sildenafil citrate, present in Sildigra 250 mg, works by inhibiting PDE5, effectively reducing its activity.