IBMX is one of the most potent and nonspecific inhibitors of cyclic nucleotide PDE (phosphodiesterases) with documented IC50 values for PDE1, 2, 3, 4, and 5 equaling 19, 50, 18, 13 and 32. IBMX is documented to raise intracellular cyclic AMP levels. In rat sensory neurons the addition of IBMX caused the release of Ca2+ from caffeine ryanodine sensitive internal stores increasing the internal Ca2+ levels and inducing a biphasic membrane current response. Through PDE inhibition IBMX has also inhibited TNFα. IBMX in breast cancer cells has also induced p21 and p27 through a PKA independent pathway. Although a nonspecific PDE inhibitor IBMX does not show inhibition of PDE8B.