Effect of Rifampicin Treatment on the Metabolism of Oestradiol and 17alpha-ethinyloestradiol by Human Liver Microsomes
Overview
Affiliations
Liver biopsies were obtained from four patients treated with rifampicin 600 mg for 6-10 days. Hepatic microsomes were incubated with an NADPH-regenerating system and the substrates [2,4,6,7-3H] oestradiol, [6,7-3H] oestradiol, [2,4,6,7-3H] ethinyloestradiol and [6,7-3H] ethinyloestradiol. The hydroxylation rates of these steroids at the labelled positions of rings A and B were determined by measuring the transformation of tritium into HTO by the microsomal enzymes. Comparison with previously published data showed that treatment with rifampicin caused a fourfold increase in the rate of hydroxylation of oestradiol and ethinyloestradiol at positions C-2/C-4 of ring A and C-6/C-7 of ring B. The acceleration of oestrogen hydroxylation by rifampicin was paralleled by an increase in microsomal cytochrome P-450, and also by microsomal reduction of rifampicin-quinone, a reactive metabolite of rifampicin. The increased aromatic hydroxylation of oestradiol and ethinyloestradiol leads to enhancement of their irreversible binding to microsomal protein. The data provide an explanation for the diminished efficacy of oestrogens in contraceptive formulations given to patients under treatment with rifampicin.
Dynamic Ir(III) Photosensors for the Major Human Drug-Metabolizing Enzyme Cytochrome P450 3A4.
Denison M, Ahrens J, Dunbar M, Warmahaye H, Majeed A, Turro C Inorg Chem. 2023; 62(7):3305-3320.
PMID: 36758158 PMC: 10268476. DOI: 10.1021/acs.inorgchem.3c00059.
Roles of cytochrome P450 enzymes in pharmacology and toxicology: Past, present, and future.
Guengerich F Adv Pharmacol. 2022; 95:1-47.
PMID: 35953152 PMC: 9869358. DOI: 10.1016/bs.apha.2021.12.001.
El Harrad L, Bourais I, Mohammadi H, Amine A Sensors (Basel). 2018; 18(1).
PMID: 29315246 PMC: 5795370. DOI: 10.3390/s18010164.
Li A, Hartman N, Lu C, Collins J, Strong J Br J Clin Pharmacol. 1999; 48(5):733-42.
PMID: 10594476 PMC: 2014360. DOI: 10.1046/j.1365-2125.1999.00081.x.
Inhibition and induction of cytochrome P450 and the clinical implications.
Lin J, Lu A Clin Pharmacokinet. 1998; 35(5):361-90.
PMID: 9839089 DOI: 10.2165/00003088-199835050-00003.