PDE inhibitors

PDE inhibitors

PDE inhibitors are typically used for short-term management of heart failure or long-term management in patients awaiting heart transplant surgery. Specific PDE inhibitors are inamrinone and milrinone.

 

Pharmacokinetics

Administered I.V., inamrinone is distributed rapidly, metabolized by the liver, and excreted by the kidneys. It’s rarely used because secondary thrombocytopenia may occur as an adverse reaction.

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Milrinone is also administered I.V. It’s distributed rapidly and excreted by the kidneys, primarily as unchanged drug.

Warning!

Adverse reactions to PDE inhibitors

Adverse reactions to phosphodiesterase (PDE) inhibitors are uncommon, but the likelihood increases significantly when a patient is on prolonged therapy.

Adverse reactions may include:

• arrhythmias
• nausea and vomiting
• headache
• fever
• chest pain
• hypokalemia
• thrombocytopenia (especially with inamrinone)
• mild increase in heart rate.

Pharmacodynamics

PDE inhibitors improve cardiac output by strengthening contractions. These drugs are thought to help move calcium into the cardiac cell or to increase calcium storage in the sarcoplasmic reticulum. By directly relaxing vascular smooth muscle, they also decrease peripheral vascular resistance (afterload) and the amount of blood returning to the heart (preload).

Pharmacotherapeutics

Inamrinone and milrinone are used to manage heart failure in patients who haven’t responded adequately to treatment with cardiac glycosides, diuretics, or vasodilators. Prolonged use of these drugs may increase the patient’s risk of complications and death. 

 

Drug interactions

• PDE inhibitors may interact with disopyramide, causing hypotension.
• Because PDE inhibitors reduce serum potassium levels, taking