Cipram Drug Interactions

Citalopram is neither the source nor the cause of clinically important drug-drug interactions.
Pharmacodynamic interactions: At the pharmacodynamics level, there have only been few documented cases of serotonin syndrome with citalopram and moclobemide and buspirone.
Contraindicated combinations: MAOIs (non-selective as well as selective A (moclobemide)): Risk of "serotonin syndrome" (see Contraindications).
Combinations requiring precaution for use: Selegiline (selective MAO-B inhibitor): A pharmacokinetic / pharmacodynamic interaction study with concomitantly administered citalopram (20 mg daily) and selegiline (10 mg daily) (a selective MAO-B inhibitor) demonstrated no clinically relevant interactions. Patients tolerated the selegiline-citalopram combination well. The concomitant use of citalopram and selegiline (in doses above 10 mg daily) is contraindicated (see Contraindications).
Serotonergic drugs: Co-administration with serotonergic drugs (e.g. tramadol, sumatriptan) may lead to enhancement of 5-HT-associated effects.
Dynamic interactions between SSRIs and herbal remedy St. John's wort (Hypericum perforatum) can occur, resulting in an increase in undesirable effects.
Lithium and tryptophan: No pharmacodynamic interactions have been found in clinical studies in which citalopram has been given concomitantly with lithium. However, there have been reports of enhanced effects when SSRIs have been given with lithium or tryptophan and therefore the concomitant use of citalopram with these drugs should be undertaken with caution.
Haemorrhage: There have been reports of cutaneous bleeding abnormalities, such as ecchymoses and purpura, with SSRIs. Caution is advised in patients taking SSRIs, particularly with concomitant use of oral anticoagulants; drugs known to affect platelet function (e.g. atypical antipsychotics and phenothiazines, most tricyclic antidepressants, acetylsalicylic acid and non-steroidal anti-inflammatory drugs (NSAIDs), ticlopidine and dipyridamole) as well as in patients with a history of bleeding disorders (see Precautions).
ECT (electroconvulsive therapy): There are no clinical studies establishing the risks or benefits of the combined use of electroconvulsive therapy (ECT) and citalopram.
Alcohol: The combination of SSRIs and alcohol is not advisable. However, clinical studies have revealed no adverse pharmacodynamic interactions between citalopram and alcohol.
Linezolid: Serotonergic psychiatric drug should not be started in a patient receiving linezolid. Wait until 24 hours after the last dose of linezolid before starting the serotonergic psychiatric drugs.
QT interval prolongation: Pharmacokinetic and pharmacodynamic studies between citalopram and other medicinal products that prolong the QT interval have not been performed. An additive effect of citalopram and these medicinal products cannot be excluded. Therefore, co-administration of citalopram with medicinal products that prolong the QT interval, such as Class IA and III antiarrhythmics, antipsychotics (e.g. phenothiazine derivatives, pimozide, haloperidol), tricyclic antidepressants, certain antimicrobial agents (e.g. sparfloxacin, moxifloxacin, erythromycin IV, pentamidine, anti-malarial treatment particularly halofantrine), certain antihistamines (astemizole, mizolastine) etc., should only be prescribed after careful consideration.
Pharmacokinetic interactions: Biotransformation of citalopram to demethylcitalopram is mediated by CYP2C19 (approx. 38%), CYP3A4 (approx. 31%) and CYP2D6 (approx. 31%) isozymes of the cytochrome P450 system. The fact that citalopram is metabolised by more than one CYP means that inhibition of its biotransformation is less likely and co-administration of citalopram with other drugs in clinical practice has very low likelihood of producing pharmacokinetic drug interactions (see Dosage & Administration and Precautions).
Influence of other medicinal products on the pharmacokinetics of citalopram: Co-administration with ketoconazole (potent CYP3A4 inhibitor) did not change the pharmacokinetics of citalopram.
A pharmacokinetic interaction study of lithium and citalopram did not reveal any pharmacokinetic interactions.
Cimetidine (potent CYP2D6, 3A4 and 1A2 inhibitor) caused a moderate increase in the average steady state levels of citalopram. Caution is advised when administering citalopram in combination with cimetidine. Dose adjustment may be warranted (see Dosage & Administration and Precautions).
Effects of citalopram on other medicinal products: A pharmacokinetic / pharmacodynamic interaction study with concomitant administration of citalopram and metoprolol (a CYP2D6 substrate) showed a two-fold increase in metoprolol concentrations, but no statistically significant increase in the effect of metoprolol on blood pressure and heart rate in healthy volunteers.
Citalopram and demethylcitalopram are negligible inhibitors of CYP2C9, CYP2E1 and CYP3A4, and only weak inhibitors of CYP1A2, CYP2C19 and CYP2D6 as compared to other SSRIs established as significant inhibitors.
Thus, no change in pharmacokinetics or only very small changes of no clinical importance were observed when citalopram was given with CYP1A2 substrates (clozapine and theophylline), CYP2C9 (warfarin), CYP2C19 (imipramine and mephenytoin), CYP2D6 (sparteine, imipramine, amitriptyline, risperidone) and CYP4A4 (warfarin, carbamazepine and triazolam).
In a pharmacokinetic interaction study, citalopram did not cause any changes in the pharmacokinetics of digoxin meaning that citalopram neither induces nor inhibits P-glycoprotein.