Turning off the IP3 cascade
IP3 is indeed degraded, this is done by a specific phosphatase which is called &quot;Phosphoinositide 5-phosphatase (INPP5A)&quot;. It catalyzes the reaction in the following way:
1-phosphatidyl-1D-myo-inositol 4,5-bisphosphate + H2O $⇌$ 1-phosphatidyl-1D-myo-inositol 4-phosphate + phosphate
The enzyme cuts of the 5'-Phosphate group and leaves 1,4-Inositolphosphate, which is subsequently recycled. The schematics looks like this in the left side (figure 1 from the reference):

Reference:
Inositol trisphosphate 3-kinases: focus on immune and neuronal signaling