Stereoselectivity in the metabolism of the .BETA.-adrenergic blocking agent, (.+-.)-1-tert-butylamino-3-(2,3-dimethylphenoxy)-2-propanol hydrochloride (xibenolol hydrochloride, D-32), in man.
作者:SEIJIRO HONMA、TOMIHARU ITO、AKIRA KAMBEGAWA
DOI:10.1248/cpb.33.760
日期:——
After oral administration of deuterium-labeled pseudoracemic D-32 to human subjects, the enantiomeric metabolites in plasma and urine were analyzed by gas chromatography-mass spectrometry. D-32 was biotransformed to 3 major metabolites, 4-hydroxy D-32, 3-hydroxymethyl D-32 and 3-carboxy D-32. Twenty-five percent of the racemic dose was excreted into the urine as 4-hydroxy D-32, and 80% of 4-hydroxy D-32 in the urine was derived from (-)-D-32. Sixty percent of 3-carboxy D-32 in the urine was derived from (+)-D-32. About 1% of the racemic dose was excreted into the urine as unchanged material, but of this, in which (+)-D-32 amounted to 3-5 times more than (-)-D-32. The area under the plasma concentration-time curve of (-)-4-hydroxy D-32 was 2.6 times larger than that of (+)-4-hydroxy D-32. The half-lives of (-)-4-hydroxy D-32, (+)-4-hydroxy D-32 and both enantiomers of D-32 were 3.8, 2.4 and 3h, respectively. Thus, a marked difference in the metabolism between (-)-D-32 and (+)-D-32 was found. As 4-hydroxy D-32 and 3-hydroxymethyl D-32 are the active metabolites, the pharmacological effectiveness of D-32 after oral administration is represented by the total amount of (-)-4-hydroxy D-32 and (-)-3-hydroxymethyl D-32.
口服给药氘标记的伪外消旋D-32后,分析了人类受试者血浆和尿液中的对映体代谢物,采用气相色谱-质谱法。D-32转化为三种主要代谢物,分别是4-羟基D-32、3-羟甲基D-32和3-羧基D-32。25%的外消旋剂量以4-羟基D-32的形式排泄到尿液中,尿液中80%的4-羟基D-32来源于(-)-D-32。尿液中60%的3-羧基D-32来源于(+)-D-32。约1%的外消旋剂量以未改变的物质形式排泄到尿液中,其中(+)-D-32的量是(-)-D-32的3-5倍。(-)-4-羟基D-32的血浆浓度-时间曲线下面积是(+)-4-羟基D-32的2.6倍。(-)-4-羟基D-32、(+)-4-羟基D-32以及两种D-32对映体的半衰期分别为3.8小时、2.4小时和3小时。因此,发现(-)-D-32和(+)-D-32在代谢上存在显著差异。由于4-羟基D-32和3-羟甲基D-32是活性代谢物,因此口服给药后D-32的药效由(-)-4-羟基D-32和(-)-3-羟甲基D-32的总量决定。