Tadalafil, the active ingredient in Apcalis Oral Jelly, is a phosphodiesterase type 5 (PDE5) inhibitor. It works by relaxing the blood vessels in the penis, which increases blood flow and helps achieve and maintain an erection when sexually aroused. It also helps alleviate symptoms of benign prostatic hyperplasia (BPH) by relaxing the muscles in the prostate and bladder.