RT Book, Section A1 Suyderhoud, Johan P. A2 Freeman, Brian S. A2 Berger, Jeffrey S. SR Print(0) ID 1102569702 T1 Phosphodiesterase Inhibitors T2 Anesthesiology Core Review: Part One Basic Exam YR 2014 FD 2014 PB McGraw-Hill Education PP New York, NY SN 9780071821377 LK accessanesthesiology.mhmedical.com/content.aspx?aid=1102569702 RD 2024/04/23 AB Phosphodiesterase inhibitors (PDEI) are a broad category of drugs that act to prevent the hydrolysis of cyclic 3,5 adenosine monophosphate (cAMP) and 3,5 guanosine monophosphate (cGMP) by phosphodiesterases. Phosphodiesterases (PDEs) are a heterogeneous group of at least 11 isoenzymes, with over 50 isoforms, present in a wide variety of tissues, and their actions are important in regulating intracellular levels of cAMP and cGMP, both important components of intracellular second messenger systems. Inhibition of phosphodiesterases will lead to an increase in intracellular cyclic nucleotides and amplify their actions in various organ beds. The main clinical interest of anesthesiologists resides with the direct effects of PDEIs in cardiac and vascular tissue mediated by the PDEI type III (3) isoenzyme. Other PDEIs have clinical applications in treating primary pulmonary hypertension, persistent pulmonary hypertension of the newborn, and erectile dysfunction (PDEI type 5); this will be discussed briefly at the conclusion of this chapter. PDEI, primarily type 4, may also prove to be of benefit in treating inflammatory (eg, reactive airway disease) and some neoplastic disease states (where cAMP levels have found to be reduced).