Theobromine, a xanthine alkaloid isolated and purified from the fruits of Theobroma cacao L., is widely consumed as stimulants and snacks in coffee and cocoa based foods and most often as part of ingredients in drugs.

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

Doxofylline is a methylxanthine bronchodilator used to treat asthma, COPD and bronchospasm, whiel the anti-asthmatic effects are mediated primarily through inhibiting the activities of the phosphodiesterase (PDE) enzyme.

Amrinone is a type 3 pyridine phosphodiesterase inhibitor used in the treatment of congestive heart failure.

Vardenafil HCl is a type PDE inhibitor with IC50 of 0.7 and 180 nM for PDE5 and PDE1, respectively.

Tadalafil is a PDE5 inhibitor with an IC50 value of 1.8 nM.

Sildenafil citrate, one of the selective phosphodiesterase-5 (PDE5) inhibitors (IC50= 5.22 nM), is considered the best treatment for erectile dysfunction.

Avanafil is a potent and highly selective phosphodiesterase-5 (PDE-5) inhibitor with IC50 of 5.2 nM for erectile dysfunction, exhibiting lower selectivity against PDE1, PDE6, and PDE11.

Dipyridamole is a phosphodiesterase inhibitor that blocks uptake and metabolism of adenosine by erythrocytes and vascular endothelial cells.

Pimobendan is a selective inhibitor of PDE3 with IC50 of 0.32 μM.

Theophylline is a natural product present in tea and cocoa, working as a phosphodiesterase inhibitor, adenosine receptor blocker, and histone deacetylase activator.

Dyphylline, a xanthine derivative, acts as an adenosine receptor antagonist and phosphodiesterase inhibitor, which is used in the treatment of respiratory disorders.

Proxyphylline is a xanthine-derivatived antagonists of A1 and A2 adenosine receptors, which relaxe smooth muscles, particularly bronchial muscles.

Acefylline is an adenosine receptor antagonist, a stimulant drug of the xanthine chemical class.

Roflumilast N-oxide, an active metabolite of roflumilast, is an inhibitor of phosphodiesterase 4 (PDE4). It can be combined with formoterol to enhance the antiinflammatory effect of dexamethasone.

Enoximone is an inotropic vasodilating agent and a selective and orally active phosphodiesterase III (PDE3) inhibitor with an IC50 of 5.9 μM. Enoximone induces vasodilatation and increases intracellular levels of cAMP by inhibiting cGMP-inhibited PDE. Enoximone also exhibits PDE4 inhibitory effect with an IC50 of 21.1 μM for myocardial PDE4A. Enoximone has the potential for congestive heart failure research and has bronchodilatory, antiasthma and anti-inflammatory effects.

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.

BRL-50481 is an inhibitor of PDE7 with IC50 of 0.15 μM and can also inihibt PDE7A, PDE7B, PDE4 and PDE3. BRL-50481 has been shown to increase mineralisation activity in osteoblasts thus has the potential treatment of osteoporosis.

Icariin is a cGMP-specific PDE5 inhibitor with IC50 of 0.432 μM, 167-fold selective for PDE5 than PDE4 and exhibits multiple biological properties, including anti-inflammatory, neuroregulatory and neuroprotective activities. It is a major constituent of flavonoids from the Chinese medicinal herb Epimedium brevicornum..

Dibutyryl-cAMP inhibits neuronal glucose uptake via PKA activation.