I take "paroxetine HCL 20mg" my doctor prescribed to me for anxiety. It greatly helps me control my heart rate when i'm having an anxiety attack and reduces how frequently i get them but it helps delay ejaculation too.
Without it, sex for me would last 5-10 minutes before ejaculation. With half a pill I could do 15-20 minutes. With a full pill I could do 30 minutes+ an can feel every sensation. But if i take a full pill daily, say for a week, I could go for way longer but the sensation you feel decreases.
Therefore, when I know i'm going to get some action, i always take a full pill the day before.