Catonia in bipolar I is similar to that in schizophrenia, as they’re both believed to be caused by irregularities in dopamine and glutamate.
Thus the treatments for catonia in bipolar I are similar to those of sz. The most common treatment is a benzodiazepine. Specifically lorazapam (Ativan). Most patients respond to this med as a first line treatment.
Other treatments are atypical APs, ECT (as sungirl said), and TMS (transcranial magnetic stimulation).
If the catonia is interfering with ADLs, then it needs to be treated assertively.
I hope this helps in some way.
Blessings,
Anthony