Betahistine
DrugThe study will be comprised of three treatment periods for a total of 4 weeks treatment duration:
Period I 1 week (Days 1-7) administration of betahistine 48 mg three times daily (144 mg/day total) or matching placebo Period II 1 week (Days 8-14) titration of olanzapine once daily (from 2.5 mg up to 10 mg) and continuation of betahistine or matching placebo administration (three times daily as in Period I) Period III 2 weeks (Days 15-28) of co-administration of betahistine or matching placebo (three times daily; as in Periods II and III) and olanzapine once daily (7.5 or 10 mg, as tolerated)
On Day 1, after a 7-day screening period, eligible subjects will be randomized to one of the two treatment groups in a 1:1 ratio:
Betahistine 48 mg TID; 08:00, 13:00 and 18:00 (144 mg/day total) Matching placebo TID; 08:00, 13:00 and 18:00