title: Two cases of mild serotonin toxicity via 5-hydroxytryptamine 1A receptor stimulation.
abstract: We propose the possibility of 5-hydroxytryptamine (5-HT)1A receptor involvement in mild serotonin toxicity. A 64-year-old woman who experienced hallucinations was treated with perospirone (8 mg/day). She also complained of depressed mood and was prescribed paroxetine (10 mg/day). She exhibited finger tremors, sweating, coarse shivering, hyperactive knee jerks, vomiting, diarrhea, tachycardia, and psychomotor agitation. After the discontinuation of paroxetine and perospirone, the symptoms disappeared. Another 81-year-old woman, who experienced delusions, was treated with perospirone (8 mg/day). Depressive symptoms appeared and paroxetine (10 mg/day) was added. She exhibited tachycardia, finger tremors, anxiety, agitation, and hyperactive knee jerks. The symptoms disappeared after the cessation of paroxetine and perospirone. Recently, the effectiveness of coadministrating 5-HT1A agonistic psychotropics with selective serotonin reuptake inhibitors (SSRIs) has been reported, and SSRIs with 5-HT1A agonistic activity have been newly approved in the treatment of depression. Perospirone is a serotonin-dopamine antagonist and agonistic on the 5-HT1A receptors. Animal studies have indicated that mild serotonin excess induces low body temperature through 5-HT1A, whereas severe serotonin excess induces high body temperature through 5-HT2A activation. Therefore, it could be hypothesized that mild serotonin excess induces side effects through 5-HT1A, and severe serotonin excess induces lethal side effects with hyperthermia through 5-HT2A. Serotonin toxicity via a low dose of paroxetine that is coadministered with perospirone, which acts agonistically on the 5-HT1A receptor and antagonistically on the 5-HT2A receptor, clearly indicated 5-HT1A receptor involvement in mild serotonin toxicity. Careful measures should be adopted to avoid serotonin toxicity following the combined use of SSRIs and 5-HT1A agonists.
authors.affiliation: Yamaguchi Prefecture Mental Health Medical Center, Yamaguchi, Japan.
authors.forename: Hiroto
authors.initials: H
authors.lastname: Nakayama
authors.affiliation: Department of Psychiatry, NTT West Osaka Hospital, Osaka, Japan.
authors.forename: Sumiyo
authors.initials: S
authors.lastname: Umeda
authors.affiliation: Department of Psychiatry, National Defense Medical College, Saitama, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Nibuya
authors.affiliation: Department of Neuropsychiatry, Oita University Faculty of Medicine, Oita, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Terao
authors.affiliation: Department of Psychiatry, Jichi University School of Medicine, Tochigi, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Nisijima
authors.affiliation: Department of Psychiatry, National Defense Medical College, Saitama, Japan.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Nomura
keywords: 5-HT1A; 5-HT2A; paroxetine; perospirone; serotonin toxicity