Identification of CYP3A4 as the predominant isoform responsible for the metabolism of ambroxol in human liver microsomes.

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Ishiguro N, Senda C, Kishimoto W, Sakai K, Funae Y, Igarashi T

Identification of CYP3A4 as the predominant isoform responsible for the metabolism of ambroxol in human liver microsomes.

Xenobiotica. 2000 Jan;30(1):71-80.

PubMed ID

10659952 [ View in PubMed

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Abstract

1. In humans, ambroxol is metabolized to dibromoanthranilic acid (DBAA) and 6,8-dibromo-3-(trans-4-hydroxycyclohexyl)-1,2,3,4-tetrahydroquinazoli ne (DHTQ). The formation of DHTQ proceeds non-enzymatically, whereas that of DBAA requires NADPH. Studies have been performed to identify the CYP isozyme(s) involved in the formation of DBAA using human liver microsomes and microsomes expressing recombinant human CYP isozymes (1A1, 1A2, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4 and 4A11). 2. The apparent Vmax and Km for the formation of DBAA were 472+/-192 pmol/ min/mg protein and 248+/-40.6 microM respectively (mean +/- S.D., n = 3). 3. Of the recombinant CYP examined, only CYP3A4 metabolized ambroxol to DBAA. The apparent Vmax and Km were 1.42 pmol/min/pmol P450 and 287 microM respectively. 4. Among the CYP inhibitors examined (furafylline, sulphaphenazole, quinidine, diethyldithiocarbamic acid, ketoconazole), only ketoconazole inhibited the production of DBAA (> 80%) at 1 microM and anti-CYP3A antiserum almost completely inhibited the formation of DBAA. 5. These results suggest that CYP3A4 is predominantly involved in the metabolism of ambroxol to DBAA in humans.

DrugBank Data that Cites this Article

Drug Enzymes

Drug	Enzyme	Kind	Organism	Pharmacological Action	Actions
Ambroxol	Cytochrome P450 3A4	Protein	Humans	Unknown	Substrate	Details