Arai Motomi, Iwabuchi Masayasu
Department of Neurology, Seirei Mikatahara General Hospital, 3453 Mikatahara-cho, Hamamatsu, Shizuoka, 433-8558, Japan.
BMJ Case Rep. 2009;2009. doi: 10.1136/bcr.01.2009.1484. Epub 2009 Mar 26.
A 60-year-old man with Parkinson's disease developed hyponatraemia with low plasma osmolarity, urine hyperosmolarity and an elevated urine sodium concentration. Plasma vasopressin (AVP) level was five times the upper normal limit and a diagnosis of the syndrome of inappropriate antidiuresis (SIAD) was made. Although the patient was treated with levodopa/carbidopa 500 mg/50 mg, entacapone 400 mg, seregiline 5 mg, cabergoline 1 mg, pergolide 250 μg and pramipexole 3 mg, SIAD resolved after the dose reduction of pramipexole. Dopamine is reported to facilitate AVP secretion through activation of D4 receptors. The hD4:hD2L pKi ratio calculated from published data is 0.017 for cabergoline, 0.44 for pergolide, 1.1 for ropinirole and 13 for pramipexole. The hD4:hD2 pKi ratio of dopamine is reported to be 1. Accordingly, pramipexole has a higher selectivity for D4 receptor than other dopamine agonists. Pramipexole is likely to increase AVP secretion, which is a prerequisite for developing SIAD.
一名60岁帕金森病男性患者出现低钠血症，伴有血浆渗透压降低、尿渗透压升高及尿钠浓度升高。血浆血管加压素（AVP）水平是正常上限的5倍，诊断为抗利尿激素分泌失调综合征（SIAD）。尽管该患者接受了左旋多巴/卡比多巴500mg/50mg、恩他卡朋400mg、司来吉兰5mg、卡麦角林1mg、培高利特250μg和普拉克索3mg治疗，但在普拉克索剂量减少后，SIAD得以缓解。据报道，多巴胺可通过激活D4受体促进AVP分泌。根据已发表数据计算，卡麦角林的hD4:hD2L pKi比值为0.017，培高利特为0.44，罗匹尼罗为1.1，普拉克索为13。据报道，多巴胺的hD4:hD2 pKi比值为1。因此，普拉克索对D4受体的选择性高于其他多巴胺激动剂。普拉克索可能会增加AVP分泌，这是发生SIAD的一个先决条件。
