RT Journal Article
SR Electronic
T1 In vitro metabolism of dorzolamide, a novel potent carbonic anhydrase inhibitor, in rat liver microsomes.
JF Drug Metabolism and Disposition
JO Drug Metab Dispos
FD American Society for Pharmacology and Experimental Therapeutics
SP 916
OP 921
VO 22
IS 6
A1 Hasegawa, T
A1 Hara, K
A1 Kenmochi, T
A1 Hata, S
YR 1994
UL http://dmd.aspetjournals.org/content/22/6/916.abstract
AB The in vitro metabolism of dorzolamide, a potent carbonic anhydrase inhibitor, was investigated using liver microsomes from Sprague-Dawley rats. The liver microsomes metabolized dorzolamide to an N-deethylated form, whereas N-deethylation of dorzolamide was not detected in 10,000g supernatant from the small intestine, brain, heart, lung, kidney and spleen, or the cytosol fraction of liver. The dorzolamide N-deethylase activity was not detected without an NADPH-generating system and was inhibited by classical inhibitors for cytochrome P450, metyrapone and n-octylamine. Orphenadrine and diphenhydramine (specific inhibitors for CYP2B1/2), diethyldithiocarbamate, disulfiram and isoniazid (inhibitors for CYP2E1), troleandomycin (inhibitor for CYP3A), and testosterone inactivated dorzolamide N-deethylase activity. On the other hand, ajmalicine, a specific inhibitor for CYP2D1, did not inhibit the reaction. With phenobarbital-induced microsomes, 66%, 72%, 36%, and 53% of the 2 beta-, 6 beta-, 16 alpha-, and 16 beta-testosterone hydroxylase activities were inhibited by 5 mM dorzolamide, respectively, whereas the 2 alpha-hydroxylase activity was not inactivated. Antisera against rat CYP2B1, CYP2E1, and CYP3A2 suppressed dorzolamide N-deethylase activity by 52%, 43% and 46%, respectively, whereas only 18% and 15% of the activity were inhibited by anti-CYP1A1 and anti-CYP4A1 antibodies, respectively. Analysis of the N-deethylase reactions using Eadie-Scatchard plots showed high- and low-affinity components in rat liver microsomes. The high-affinity reaction was induced with phenobarbital and dexamethasone, but not with 3-methylcholanthrene. These results suggest that CYP2B, CYP2E1, and CYP3A subfamilies are involved in the dorzolamide N-deethylation in rat liver microsomes.