Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor and works by relaxing the blood vessels. It can improve blood flow to the penis and helps to get an erection when sexually stimulated. Dapoxetine is a short-acting selective serotonin reuptake inhibitor (SSRI) that increases the serotonin levels in the brain, thereby increasing the time to ejaculate and improving the control over ejaculation.