Hello dear now you can understand mania and depression, the condition in general is called bipolar affective disorder.
In manic phase antipsychotic is needed.
You said previously he was taking olanzapine, how was the response on olanzapine.? If it was good than you should continue it.
Rule out any history of
diabetes and hypertension first.
Next Steps
If he is not taking olanzapine oral tablet than one formulation called as DT is available in mkt U can mix with it in food also. Eg oleptal DT.
Liquid formula of another antipsychotic risperidone is also available, you can mix it in food and juice.