Phosphodiesterase 3 (PDE3) family members have high-affinities for both cAMP and cGMP and show cGMP-dependent inhibition of cAMP hydrolysis. Milrinone is a potent inhibitor of type 3 phosphodiesterases (PDEs), inhibiting recombinant PDE3A and PDE3B with IC50 values of 0.45 and 1.0 μM, respectively. It less effectively inhibits other PDE isoforms, with IC50 values of 263, >300, 17.5, 49.1, and 58.3 μM for PDE1, PDE2, PDE4, PDE5, and PDE7, respectively. Milrinone has positive inotropic (stimulates cardiac muscle contractions) and vasodilatory effects when administered in vivo.
