One or two meds for SZA bipolar type?

Hi, my son is taking Haldol LAI for SZA bipolar type. Is monotherapy enough or does he need a core moodstabilizer like lithium added in? He has just come out of psychosis after three months and is having small mood swings at the moment. Pdoc thinks Haldol will stabilize his moods, he has been taking it for 6 weeks.