Suhagra 25 mg belongs to the class of drugs known as phosphodiesterase type 5 (PDE5) inhibitors. PDE5 is an enzyme found primarily in the smooth muscle of the corpus cavernosum (penile tissue) and pulmonary vasculature. Inhibition of PDE5 increases the levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation and increased blood flow to certain areas of the body.