The localization of substance P in brain regions that coordinate stress responses and receive convergent monoaminergic innervation suggested that substance P antagonists might have psychotherapeutic properties. Like clinically used antidepressant and anxiolytic drugs, substance P antagonists suppressed isolation-induced vocalizations in guinea pigs. In a placebo-controlled trial in patients with moderate to severe major depression, robust antidepressant effects of the substance P antagonist MK-869 were consistently observed. In preclinical studies, substance P antagonists did not interact with monoamine systems in the manner seen with established antidepressant drugs. These findings suggest that substance P may play an important role in psychiatric disorders.
This 7- to 8-week, multicenter, randomized, double-blind, placebo-controlled study was performed to determine the dose-effect relationship and minimum effective dose for fluvoxamine maleate in a titrated fixed-dose study of major depressive disorder. Gradual titration over 2 weeks to fixed maintenance doses was employed to minimize dropout due to initial side effects. The study enrolled 600 outpatients, male and female, age 18-65, meeting DSM-III-R criteria for major depressive disorder. A 13-item subscore of the standard 21-Item Hamilton Depression Scale was used to minimize the possible contribution of known side effects from serotonin reuptake inhibitors to the overall HAM-D score. Secondary efficacy assessments included the HAM-D retardation factor, HAM-D depressed mood item, CGI-severity of illness item, and SCL depression factor. Fluvoxamine (50-150 mg/day) was therapeutically effective and well tolerated during 6 weeks of therapy. Based on the HAM-D depressed mood item, efficacy was dose dependent. The minimum effective dose was 50 mg/day. Fluvoxamine maleate shows dose-related effectiveness in the acute treatment of major depressive disorder.
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