A PDE3 inhibitor is a drug which inhibits the action of the phosphodiesterase enzyme PDE3. They are used for the therapy of acute heart failure and cardiogenic shock.

PDE3 inhibitors produce dilation of resistance and capacitance blood vessels (thus decreasing both preload and afterload), and exhibit positive inotropy and chronotropy. PDE3 inhibitors potentiate the effects of beta-adrenergic agonists.

Amrinone, milrinone and enoximone are used clinically for short-term treatment of cardiac failure in the presence of cardiogenic shock. PDE3 inhibitors may be preferred over catecholamines in patients with systemic or pulmonary hypertension, or in patients using beta blockers. Hypotension is often dose limiting; tachycardic and arrhythmogenic effects resemble those seen with catecholamines.

PDE3 inhibitors are indicated as inotropics for the therapy of acute heart failure if catecholamines are ineffective. However, well controlled studies have shown that PDE3 inhibitors generally increase mortality when used for the therapy of acute heart failure, so they have to be applied under close observation.

Cilostazol is used for the treatment of intermittent claudication. This drug has a much weaker positive inotropic effect than those drugs used for the therapy of acute heart failure, and lacks significant adverse cardiac effects.

Contraindications are severe obstructive cardiomyopathy, hypovolemia, tachycardia, and ventricular aneurysm. Breast feeding is prohibited during treatment.

The most important adverse effects when used for the therapy of acute heart failure are arrhythmia, thrombocytopenia and increased transaminase levels.

Approved PDE3 inhibitors include the following: