The roles of cytochrome P450 3A4 and 1A2 in the 3-hydroxylation of quinine in vivo.
OBJECTIVE
To investigate the roles of CYP3A4 and CYP1A2 in the 3-hydroxylation of quinine in vivo.


METHODS
In a randomized, three-way crossover study, nine healthy Swedish volunteers received single oral doses of quinine hydrochloride (500 mg), quinine hydrochloride (500 mg) plus ketoconazole (100 mg twice daily for 3 days), and quinine hydrochloride (500 mg) plus fluvoxamine (25 mg twice daily for 2 days) on three different occasions. Blood and urine samples were collected before quinine intake and up to 96 hours thereafter. Plasma and urine samples were analyzed for both quinine and its main metabolite 3-hydroxyquinine with HPLC methods.


RESULTS
Coadministration with ketoconazole (which inhibits CYP3A4) decreased the mean apparent oral clearance of quinine significantly (P < .001) by 31% (from 8.7 to 6.0 L/h), whereas coadministration with fluvoxamine (which inhibits CYP1A2 and to some extent CYP2C19) had no significant effect (P > .05) on the mean apparent oral clearance of quinine. Coadministration with ketoconazole also decreased the mean area under the plasma concentration versus time curve (AUC) of 3-hydroxyquinine (from 28.4 to 19.7 micromol x h x L(-1); P < .001), whereas coadministration with fluvoxamine increased 3-hydroxyquinine AUC significantly (from 28.4 to 30.2 micromol x h x L(-1); P < .05).


CONCLUSIONS
Cytochrome P450 3A4 is important for the 3-hydroxylation of quinine in vivo. On the other hand, CYP1A2 had no significant effect on this metabolic pathway.
Mirghani
R A
RA
Department of Medical Laboratory Sciences and Technology, Karolinska Institutet at Huddinge University Hospital, Sweden.
Hellgren
U
U
Westerberg
P A
PA
Ericsson
O
O
Bertilsson
L
L
Gustafsson
L L
LL
D000328:Adult; D000935:Antifungal Agents / Q000494:pharmacology; D000962:Antimalarials / Q000378:metabolism*; D019540:Area Under Curve; D018592:Cross-Over Studies; D019388:Cytochrome P-450 CYP1A2 / Q000378:metabolism*; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D005260:Female; D016666:Fluvoxamine / Q000494:pharmacology; D006801:Humans; D006900:Hydroxylation / Q000187:drug effects; D007654:Ketoconazole / Q000494:pharmacology; D008297:Male; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D011802:Quinidine / Q000031:analogs & derivatives* / Q000097:blood; D011803:Quinine / Q000378:metabolism*; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology
D000935:Antifungal Agents; D000962:Antimalarials; D019388:Cytochrome P-450 CYP1A2; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System; D016666:Fluvoxamine; D007654:Ketoconazole; D006899:Mixed Function Oxygenases; D011802:Quinidine; D011803:Quinine; D017367:Selective Serotonin Reuptake Inhibitors; C013569:3-hydroxyquinidine; C104464:CYP3A protein, human; C510163:CYP3A4 protein, human