Roflumilast is a selective and long-acting inhibitor of PDE-4 with IC50 of 0.8 nM.

Cilomilast is a potent PDE4 inhibitor with IC50 of about 110 nM, has anti-inflammatory activity and low central nervous system activity.

Rolipram is a selective inhibitor of phosphodiesterases PDE 4, especially the PDE 4B with IC50 of 130 nM while IC50 for PDE4D is 240 nM, it's an anti-inflammatory agent.

Apremilast is a small molecule inhibitor of PDE4 with an IC50 value of 74 nM.

Fenspiride HCl is an antagonist of α-adrenergic receptors and H1 histamine receptors and also inhibits phosphodiesterase 4 and phosphodiesterase 3 activities with logIC50 values of 4.16 and 3.44, respectively.

Luteolin is a non-selective phisphodiesterase PDE inhibitor for PDE1-5 with Kis of 15.0/6.4/13.9/11.1/9.5 μM, respectively, it is a flavonoid found in Terminalia chebula.

GSK256066 is a selective PDE4B (equal affinity to isoforms A-D) inhibitor with IC50 of 3.2 pM, showing > 380,000-fold selectivity versus PDE1/2/3/5/6 and > 2500-fold selectivity against PDE4B versus PDE7.

(S)-(+)-Rolipram is a PDE4-inhibitor and an anti-inflammatory agent, less potent than its R-enantiomer.