A bridging study of fananserin in schizophrenic patients.

Fananserin is a potential antipsychotic compound with high affinity for both D4 and 5-HT2A receptors, and negligible affinity for D2 receptors. Because the tolerance for antipsychotic compounds often differs between schizophrenic patients and healthy subjects, this bridging study was designed to evaluate the tolerability of fananserin, to define the slow titration maximum tolerated dose in the target population, and to identify the most rapid well-tolerated rate of titration for this compound. Three rates of titration regimens were examined in a total of 26 schizophrenic patients in a parallel group design, following a 3-day placebo washout period from previous antipsychotic medication. The slow rate of titration (reaching the maximum dose of 600 mg/day in 16 days with 100-mg increases every 3 days) was well tolerated, but a rapid titration schedule (reaching 600 mg/day in 8 days with 200-mg increases every 3 days) resulted in hypotension in 3 of 6 patients and termination of the group on Day 10. An intermediate rate of titration (reaching 600 mg/day in 10 days with 100-mg increases every 2 days) was then examined and was well tolerated, with transient episodes of mild hypotension reported in 2 of 10 patients. Thus, although hypotension was identified as the dose-limiting adverse event in this study, a reduction in the titration rate was effective in reducing the incidence and severity of this side effect. In this study, schizophrenic patients administered multiple doses of fananserin tolerated doses 400 percent greater than the maximum tolerated single dose in healthy volunteers.