PDE Inhibitors

Approved PDE3 inhibitors include the following:
amrinone
cilostazol
milrinone
enoximone
Pimobendane
PDE4
Apremilast, a phthalimide derivative being developed for inflammatory disorders, including psoriasis, psoriatic arthritis and ankylosing spondylitis.
Cilomilast, in clinical development
for treatment of COPD.
Diazepam, a benzodiazepine anxiolytic, amnesic, hypnotic, sedative and muscle relaxant.
Ibudilast, a neuroprotective and bronchodilator drug used mainly in the treatment of asthma and stroke. It inhibits PDE4 to the greatest extent, but also shows significant inhibition of other PDE subtypes, and so acts as a selective PDE4 inhibitor or a non-selective phosphodiesterase inhibitor, depending on the dose.
Luteolin, supplement extracted from peanuts that also possesses IGF-1 properties.
Mesembrenone, an alkaloid from the herb Sceletium tortuosum (Kanna).
Piclamilast, a more potent inhibitor than rolipram.
Roflumilast, licensed for the treatment of severe chronic obstructive pulmonary disease
Rolipram, used as investigative tool in pharmacological research.
PDE5
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 NO or statins.
Claimed newer and more-selective inhibitors are icariin, an active component of Epimedium grandiflorum,
PDE10
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
Nonselective phosphodiesterase inhibitors
Methylated xanthines and derivatives:

caffeine, a minor stimulant
aminophylline
IBMX (3-isobutyl-1-methylxanthine), used as investigative tool in pharmacological research
paraxanthine
pentoxifylline, a drug that has the potential to enhance circulation and may have applicability in treatment of diabetes, fibrotic disorders, peripheral nerve damage, and microvascular injuries
theobromine
theophylline, a bronchodilator
PDE1 selective inhibitors
Vinpocetine
Cilastatin