5-(4-Chlorobutyl)-1-cyclohexyl-d4-tetrazole is the labeled analogue of 5-(4-Chlorobutyl)-1-cyclohexyltetrazole (C365038), an impurity of Cilostazol (C441500), a potent phosphodiesterase III A (PDE3A) inhibitor (IC50=0.2uM) and inhibitor of adenosine uptake. Has antimitogeni, antithrombotic, vasodilatory and cardiotonic properties in vivo. Also affects lipid levels in vivo.