Forzest 20 mg is a medication that contains tadalafil as its active ingredient. Tadalafil is a phosphodiesterase type 5 (PDE5) inhibitor, similar to sildenafil (Viagra) and vardenafil (Levitra). Forzest 20 mg is primarily used for the treatment of erectile dysfunction (ED), a condition where a man has difficulty achieving or maintaining an erection sufficient for sexual activity.