Icariin (Ieariline) belongs to the flavonol glycoside group of natural products, can inhibit PDE5 and PDE4 activity (IC50=432/73.50 μM), is also a PPARα activator. Icariin can increase cardiovascular and cerebrovascular blood flow, promote hematopoiesis, immunity and bone metabolism.

Theophylline monohydrate (Quibron) appears to inhibit phosphodiesterase and prostaglandin production, regulate calcium flux and intracellular calcium distribution, and antagonize adenosine. Theophylline monohydrate is a natural alkaloid derivative of xanthine isolated from the plants Camellia sinensis and Coffea arabica. Physiologically, this agent relaxes the bronchial smooth muscle, produces vasodilation (except in cerebral vessels), stimulates the CNS, stimulates the cardiac muscle, induces diuresis, and increases gastric acid secretion; it may also suppress inflammation and improve contractility of the diaphragm.

Indomethacin (Indomethacin) is a COX1 and COX2 inhibitor (IC50=18/26 nM) with blood-brain barrier permeability and non-selectivity. Indomethacin is a non-steroidal anti-inflammatory agent with anti-tumor and anti-infective activity.

Isoprenaline hydrochloride (NCI-c55630) is a potent beta-adrenergic agonist with the peripheral vasodilator, bronchodilator, and cardiac stimulating properties.

Roflumilast (APTA 2217) is an orally available, long-acting inhibitor of phosphodiesterase (PDE) type 4 (PDE4), with anti-inflammatory and potential antineoplastic activities. Upon administration, roflumilast and its active metabolite roflumilast N-oxide selectively and competitively bind to and inhibit PDE4, which leads to an increase of both intracellular levels of cyclic-3', 5'-adenosine monophosphate (cAMP) and cAMP-mediated signaling.

Vardenafil hydrochloride is a New Phosphodiesterase Type 5(PDE5) Inhibitor, in the Treatment of Erectile Dysfunction in Men With Diabetes

Acefylline (Theophylline-7-acetic acid), a stimulant drug of the xanthine chemical class, acts as an adenosine receptor antagonist. It is combined with diphenhydramine in the pharmaceutical preparation Etanautine to help offset its stimulant effects

Diphylline (Diprophylline) is a xanthine derivative. Diphylline exerts bronchodilator effects and to a lesser extent vasodilator and diuretic properties. Diphylline probably acts as a competitive inhibitor of phosphodiesterase which leads to an increase in intracellular cAMP. This results in relaxation of bronchial smooth muscle and other smooth muscles. Diphylline may also antagonize adenosinereceptors. Diphylline is used in the treatment of acute bronchial asthma, chronic bronchitis and emphysema.