The 5-HT2 antagonists reportedly produce a paradoxical down-regulation of 5-HT2 binding sites upon chronic treatment, rather than the expected supersensitivity. Chronic treatment with ritanserin (2.5 mg/kg/day for 7 days), but not mianserin (same regimen), attenuated a QMWS 24 h after the final injection, thus supporting with a functional measure, the down-regulation of such binding sites by ritanserin.

studies after administration during the day. Full daily doses of both drugs should be prescribed in nocturnal dosing regimens, and not in divided doses over the day, for avoiding excessive sedation and performance impairment.