Interaction between Citalopram and Letrozole
Major
Metabolism
| ID | DDInter388 and DDInter1040 |
| Interaction |
Coadministration with CYP450 2C19 inhibitors may increase the plasma concentrations of citalopram, which is partially metabolized by the isoenzyme. Cases of QT interval prolongation and torsade de pointes have been reported during postmarketing use. In general, the risk of ventricular arrhythmia in association with QT prolongation is largely unpredictable, but may be increased by certain underlying risk factors such as congenital long QT syndrome, cardiac disease, and electrolyte disturbances (e.g., hypokalemia, hypomagnesemia).
abdominal distension
birth defect
abscess
adenocarcinoma
agranulocytoses
angioedema
Anxiety
aortic regurgitation
Arrhythmia
Aching joints
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| Management | Given the risk of dose-dependent QT prolongation, citalopram dosage should not exceed 20 mg/day when prescribed in combination with CYP450 2C19 inhibitors such as cimetidine, esomeprazole, etravirine, felbamate, fluconazole, lansoprazole, letrozole, modafinil, omeprazole, oxcarbazepine, ticlopidine, and voriconazole. Alternatives should be considered when possible, and hypokalemia or hypomagnesemia should be corrected prior to initiation of citalopram treatment and periodically monitored. Patients should be advised to seek medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, palpitations, irregular heartbeat, shortness of breath, or syncope. |
| References | |
| Alternative for Citalopram |
N06A
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| Alternative for Letrozole |
L02B
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Potential Metabolism Interactions
Substrate-Substrate Interaction：If more than one drug is metabolized by the same CYP, it is possible that its metabolism is inhibited because of the competition between the drugs. That means, it can be useful to lower the dosage of the drugs in the drug-cocktail because they remain longer in the organism than in monotherapy.
Inhibitor-Inhibitor Interaction：Combining two or more inhibitors of one CYP, should be compensated by lowering the dosage of these drugs because the metabolism is reduced and the drugs remain longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.
Inhibitor-Substrate Interaction：Combining drugs that have inhibitory effect and are substrates of one particular CYP, should be compensated by lowering the dosage. They rest longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.