Phosphodiesterases play an important role in the regulation of human cellular activities. Phosphodiesterases are a large family, divided into many isoforms, that function to hydrolyze intracellular second messengers and can be used to treat a variety of diseases. Depending on their physiological properties, a variety of drugs can be prepared that degrade intracellular camp or cGMP and terminate the physiological effects of these second messengers. Precautions should be taken under medical supervision when taking phosphodiesterase. When taking phosphodiesterase 5 inhibitors, it is also necessary to follow relevant precautions, such as the prohibition of taking with nitrates, which may cause intractable hypotension or even life-threatening when taken at the same time. Patients should report the relevant medical and medication history to their doctors in advance to avoid causing adverse drug reactions and jeopardizing their health.