Venlafaxine Ketoconazole

Drugs that may affect antihistamines include aluminum/magnesium-containing acids, cimetidine, erythromycin, ketoconazole, MAO inhibitors, and rifamycins (eg, rifampin). Drugs that may be affected by antihistamines include alcohol and CNS depressants, beta-blockers, MAO inhibitors, metyrapone, nefazodone, selective serotonin reuptake inhibitors (SSRIs), and venlafaxine. 

Ajmaline, ajamlicine, flecainide, fluoxetine, isoniazid, ketoconazole, lobeline, nefazodone, paroxetine, (7 )-propaphenooe, quinidine, ritonavir, "statins," yohimbine, venlafaxine... 

Theoretically the metabolism of venlafaxine may be inhibited by CYP2D6 inhibitors or substrates such as diphenhydramine, melperone, quinidine or thioridazine. CYP3A4 inhibitors such as ketoconazole may also have some effect. An isolated case describes a hypertensive crisis associated with venlafaxine and di-sulfiram. The manufacturers predict that the use of triptans with venlafaxine may have additive effects on serotonin, which could lead to the serotonin syndrome. 

Lindh JD, Annas A, Meurling L, Dahl M-L, AL-Shurbaji A. Effect of ketoconazole on venlafaxine plasma concentrations in extensive and poor metabolisers of debrisoquine. EurJ Clin Pharmacol (2003) 59, 401-6. 

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