Cialis contains tadalafil, a selective phosphodiesterase type 5 (PDE5) inhibitor developed by Eli Lilly. Its mechanism is shared with other PDE5 inhibitors: during sexual arousal, nitric oxide triggers cyclic GMP (cGMP) production, which relaxes smooth muscle and increases penile blood flow. PDE5 is the enzyme that breaks down cGMP; by inhibiting PDE5, tadalafil helps sustain […]

