<prompt> Phosphodiesterase inhibitor used for erectile dysfunctionSildenafilAmrinoneMilrinoneTamoxifen  <response>: Ref: KD Tripathi, 7th ed. pg. 303 Sildenafil is an orally active drug for treatment of ED. Sildenafil acts by selectively inhibiting PDE-5, causing increase in cGMP and enhancing Nitric Oxide action on corpus cavernosum. Amrinone and Milrinone are PDE-3 inhibitor and are also called inodilators. They are used in CHF. Tamoxifen is a selective estrogen receptor modulator, used in breast cancer. 