IBMX, also known as 1-Methyl-3-Isobutylxanthine and Isobutylmethylxanthine, is a widely-used inhibitor of cAMP and cGMP PDEs. It has been shown that the increase in cellular cAMP and cGMP levels, resulting from the inhibition of PDEs by IBMX, activates cyclicnucleotide-regulated protein kinases. IBMX does not inhibit PDE8A, PDE8B, or PDE9.