inhibitor, depending on the dose. Piclamilast, a more potent inhibitor than rolipram. Luteolin, supplement extracted from peanuts that also possesses IGF-1 properties. Drotaverine, used to alleviate renal colic pain, also to hasten cervical dilatation in labor Roflumilast, indicated for people with severe COPD to prevent symptoms such as coughing and excess mucus from worsening Apremilast, used to treat psoriasis and psoriatic arthritis. Crisaborole, used to treat atopic dermatitis. PDE4 is the major cAMP-metabolizing enzyme found in inflammatory and immune cells. PDE4 inhibitors have proven potential as anti-inflammatory drugs, especially in inflammatory pulmonary diseases such as asthma, COPD, and rhinitis. They suppress the release of cytokines and other inflammatory signals, and inhibit the production of reactive oxygen species. PDE4 inhibitors may have antidepressive effects and have also been proposed for use as antipsychotics. On October 26, 2009, The University of Pennsylvania reported that researchers at their institution had discovered a link between elevated levels of PDE4 (and therefore decreased levels of cAMP) in sleep deprived mice. Treatment with a PDE4 inhibitor raised the deficient cAMP levels and restored some functionality to Hippocampus-based memory functions. PDE5 selective inhibitors Sildenafil, tadalafil, vardenafil, and the newer udenafil and avanafil selectively inhibit PDE5, which is cGMP-specific and responsible for the degradation of cGMP in the corpus cavernosum. These phosphodiesterase inhibitors are used primarily as remedies for erectile dysfunction, as well as having some other medical applications such as treatment of pulmonary hypertension. Dipyridamole also inhibits PDE5. This results in added benefit when given together with nitric oxide or statins. PDE7 selective inhibitors Recent studies have shown Quinazoline type PDE7 inhibitor to be potent anti-inflammatory and neuroprotective agents. PDE9 selective inhibitors Paraxanthine, the main metabolite of Caffeine (84% in humans), is another cGMP-specific phosphodiesterase inhibitor which inhibits PDE9, a cGMP preferring phosphodiesterase. PDE9 is expressed as high as PDE5 in the corpus cavernosum. PDE10 selective inhibitors Papaverine, an opium alkaloid, has been reported to act as a PDE10 inhibitor. PDE10A is almost exclusively expressed in the striatum and subsequent increase in cAMP and cGMP after PDE10A inhibition (e.g. by papaverine) is "a novel therapeutic avenue in the discovery of antipsychotics". References