The in vivo mechanism of action is not entirely clear, but an inhibition of the enzyme phosphodiesterase causing elevation of cyclic AMP and cyclic GMP levels is significant. It may also alter mitochondrial respiration.<unk>  has also been demonstrated to be a selective phosphodiesterase inhibitor for the PDE10A subtype found mainly in the striatum of the brain. When administered chronically to mice, it produced motor and cognitive deficits and increased anxiety, but conversely may produce an antipsychotic effect, although not all studies support this view.
Papaverine
Oxymetazoline
Terbutaline
Erythrocrine
Piperoxan
Silodosin
Dihydroergotamine
Hyoscine butylbromide