In 2016, the U.S. Food and Drug Administration placed Viagra and other erectile dysfunction drugs collectively known as phosphodiesterase type 5 (PDE5) inhibitors on its watch list of medications with possible safety issues. (sciencedaily.com)
The inhibition of phosphodiesterase V leads to an increase in cGMP; this causes smooth muscle relaxation, which then leads to a decrease in blood pressure (hypotension).1 If the patient suffers from preexisting hypotension or is taking medications that can decrease blood pressure, sildenafil can intensify the effects. (todaysveterinarynurse.com)
The distribution of cyclic 3», 5» - nucleotide phosphodiesterase activity in rat cerebral cortex was determined by cytochemical methods. (science.sciencemag.org)