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左沙丁胺醇(levalbuterol,商品名Xopenex)是消旋沙丁胺醇的R-异构体。美国FDA已准其用于治疗大于12岁的支气管痉挛病人。厂商声称该药比消旋沙丁胺醇更安全。 药理学:沙丁胺醇是R-沙丁胺醇(左沙丁胺醇)和S-沙丁胺醇按1:1混合而成的消旋混合体。R-异构体具有扩张支气管的作用。S-异构体可使支气管缩窄,对乙酰甲胆碱的反应稍有增强,这是随着长期使用消旋沙丁胺醇所获知的。体外试验中,左沙丁胺醇与β_1和β_2-肾上腺素能受体的亲和力高于消旋沙丁胺醇。 药动学:左沙丁胺醇吸收迅速,吸入后约12h可达血药峰值。按厂方提供的资料,给予单剂量左沙丁胺醇后,其半衰期为3.3h,当给予相同剂量消旋沙丁胺醇后,其半衰期则为1.5h。重复给药后,两者的半衰期均可达4h。 临床试验:在一项双盲随机试验中,362例患轻到重度长期哮喘的病人分别使用0.63mg或1.25mg左沙丁胺醇,1.25mg或2.5mg的消旋沙丁胺醇或安慰剂,均吸入
Levalbuterol (trade name Xopenex) is the R-isomer of racemic albuterol. The U.S. FDA has approved it for the treatment of bronchospasm patients older than 12 years old. The manufacturer claims the drug is safer than racemic salbutamol. Pharmacology: Salbutamol is a racemic mixture of R-salbutamol (levalbuterol) and S-salbutamol mixed 1: 1. The R-isomer has the effect of expanding the bronchus. The S-isomer narrows the bronchus and slightly increases the response to methacholine, which is known with long-term use of racemic salbutamol. In vitro, levalbuterol has higher affinity for β_1 and β_2-adrenergic receptors than racemic salbutamol. Pharmacokinetics: left salbutamol absorption quickly, about 12h after inhalation peak blood pressure. According to the information provided by the manufacturer, given a single dose of levalbuterol, its half-life of 3.3h, when given the same dose of racemic salbutamol, its half-life was 1.5h. Repeated administration, the half-life of both up to 4h. Clinical Trials: In a double-blind, randomized trial, 362 patients with mild to severe long-term asthma were administered 0.63 mg or 1.25 mg of albuterol, 1.25 mg or 2.5 mg of racemic salbutamol, or placebo, respectively, both inhaled