My 34 Year-old Son Began Taking Zyprexa About 2 Months

My 34 year-old son began taking Zyprexa about 2 months ago. He is having several of the side effects. He is unable to work because of the side effects. He is lethargic, he doesn't feel safe driving. He is paranoid. His head hurts, and feels numb. He was on 20 mg, but has been reduced to 15 mg. He was diagnosed with bipolar type 1. What would be another better medicine for him? I have heard of DNA testing to determine the proper med for this condition.