Severe undesirable effects including serotonin syndrome w/ MAOIs. Additive effect on QT interval w/ medicinal products that prolong QT interval eg, Class IA & III antiarrhythmics, antipsychotics (eg, phenothiazine derivatives, pimozide, haloperidol), TCAs, certain antimicrobial agents (eg, sparfloxacin, moxifloxacin, erythromycin IV, pentamidine, antimalarial treatment particularly halofantrine), certain antihistamines (astemizole, mizolastine). Enhanced effects w/ lithium or tryptophan; serotonergic medicinal products (eg, tramadol, sumatriptan). Increased undesirable effects w/ St. John’s wort. Increased risk of haemorrhage w/ anticoagulants, medicinal products that affect platelet function eg, NSAIDs, acetylsalicylic acid, dipyridamole, & ticlopidine or other medicines (eg, atypical antipsychotics). Combination w/ alcohol is not advisable. Increased risk of malignant arrhythmias w/ hypokalaemia-/hypomagnesaemia-inducing medicinal products. Additive effect w/ medicinal products capable of lowering seizure threshold (eg, antidepressants [SSRIs], neuroleptics [thioxanthenes & butyrophenones]), mefloquine, bupropion & tramadol). Moderate increase in the average steady state levels w/ cimetidine (potent CYP2D6, 3A4 & 1A2 inhibitor). Increased plasma conc of escitalopram (active enantiomer of citalopram) w/ omeprazole & other CYP2C19 inhibitor (eg, esomeprazole, fluvoxamine, lansoprazole, ticlopidine). Increased plasma levels of CYP2D6 substrate (eg, metoprolol). Increased plasma conc of desipramine (primary metabolite of imipramine).