Comment
Author: Admin | 2025-04-28
And CYP2C19 are the primary enzymes involved in the metabolism of citalopram, it is expected that potent inhibitors of CYP3A4 (e.g., ketoconazole, itraconazole, and macrolide antibiotics) and inhibitors of CYP2C19 (e.g., omeprazole, cimetidine) might decrease the clearance of citalopram. However, co-administration of citalopram and the potent CYP3A4 inhibitor ketoconazole did not significantly affect the pharmacokinetics of citalopram. 20 mg/day is the maximum recommended citalopram dose in patients taking concomitant cimetidine or another CYP2C19 inhibitor, because of the risk of QT prolongation [see Dosage and Administration (2.2), Warnings and Precautions (5.2)]. Cimetidine In subjects who had received 21 days of 40 mg/day citalopram hydrobromide, combined administration of 400 mg twice a day cimetidine for 8 days resulted in an increase in citalopram AUC and Cmax of 43% and 39%, respectively [see Dosage and Administration (4), Warnings and Precautions (5.2), Drug Interactions (7)]. CYP2D6 Inhibitors Co-administration of a drug that inhibits CYP2D6 with citalopram is unlikely to have clinically significant effects on citalopram metabolism, based on the study results in CYP2D6 poor metabolizers. Digoxin In subjects who had received 21 days of 40 mg/day citalopram hydrobromide, combined administration of citalopram hydrobromide and digoxin (single dose of 1 mg) did not significantly affect the pharmacokinetics of either citalopram or digoxin. Lithium Co-administration of citalopram hydrobromide (40 mg/day for 10 days) and lithium (30 mmol/day for 5 days) had no significant effect on the pharmacokinetics of citalopram or lithium. Pimozide In a controlled study, a single dose of pimozide 2 mg co-administered with citalopram 40 mg given once daily for 11 days was associated with a mean increase in QTc values of approximately 10 msec compared to pimozide given alone. Citalopram did not alter the mean AUC or Cmax of pimozide. The mechanism of this pharmacodynamic interaction is not known [see Contraindications (4), Warnings and Precautions (5.2)]. Theophylline Combined administration of citalopram hydrobromide (40 mg/day for 21 days) and the CYP1A2 substrate theophylline (single dose of 300 mg) did not affect the pharmacokinetics of theophylline. The effect of theophylline on the pharmacokinetics of citalopram was not evaluated. Warfarin Administration of 40 mg/day citalopram hydrobromide for 21 days did not affect the pharmacokinetics of warfarin, a CYP3A4 substrate. Prothrombin time was increased by 5%, the clinical significance of which is unknown. Carbamazepine Combined administration of citalopram hydrobromide (40 mg/day for 14 days) and carbamazepine (titrated to 400 mg/day for 35 days) did not significantly affect
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