Drug interactions venlafaxine

Although many patients believe that dietary supplements will not interact with medications, recent literature suggests otherwise. Recently, many St. John s wort-drug interactions have been reported in the literature. Cases of patients developing symptoms of serotonin syndrome have been reported with St. John s wort alone and in concomitant therapy with other antidepressants such as monoamine oxidase inhibitors, serotonin reuptake inhibitors, and venlafaxine. St. John s wort may exacerbate the sedative effects of benzodiazepines, alcohol, narcotics, and other sedatives. St. John s wort may decrease the levels of protease inhibitors, cyclosporine, digoxin, and theophylline. 

Venlafaxine is metabolized to its active metabolite, ODV, by cytochrome P-450 2D6. Therefore, the potential exists for a drug interaction between venlafaxine and drugs that inhibit this isoenzyme. 

Ereshefsky L, Dugan D (2000) Review of the pharmacokinetics, pharmacogenetics, and drug interactions potential of antidepressants focus on venlafaxine. Depress Anxiety 12(Suppl l) 30-44... 

The coadministration of venlafaxine and MAOls is contraindicated because of the risk of serotonin syndrome. Venlafaxine is a relatively weak inhibitor of the CYP450-2D6 system, therefore it has few drug interactions (Ball et al. 1997). 

Given the use of venlafaxine for treatment-refractory depression in adults, it is likely that it will be used for similar purposes in children. In addition, it is likely that venlafaxine will be used for childhood anxiety disorders. It is unclear whether venlafaxine is serotonergi-cally powerful enough to be useful in OCD. The lack of significant drug-drug interactions may facilitate its use in patients for whom antidepressant medication combinations are anticipated. 

Because most antidepressants require oxidative metabolism as a necessary step in their elimination, they can be the target of a pharmacokinetic drug-drug interaction, as well as the cause. The CYP enzymes mediating the biotransformation of the various antidepressants are also shown in Table 7-30. CYP 1A2 and 3A3/4 are induced by anticonvulsants such as barbiturates and carbamazepine. As expected, coadministration of these anticonvulsants has been shown to lower plasma levels of TCAs and would be predicted to have the same effect on nefazodone, sertraline, and venlafaxine. 

Although venlafaxine can have more interactions than SSRIs pharmacodynamically, it is comparable with citalopram and sertraline in terms of not causing CYP enzyme mediated pharmacokinetic drug-drug interactions (Table 7-29). Thus, these three antidepressants have a distinct advantage over drugs such as fluoxetine, particularly in patients who are likely to be on other medications in aaaition to their antidepressant. 

Levin GM, Nelson LA, DeVane CL, Preston SL, Eisele G, Carson SW. A pharmacokinetic drug-drug interaction study of venlafaxine and indinavir. Psychopharmacol Bull 2001 35(2) 62-71. 

LITHIUM OTHER-VENLAFAXINE Possible risk of serotonin syndrome Additive effect Be aware of the possibility of serotonin syndrome. Also need to monitor lithium levels with appropriate dose adjustments during co-administration >- For signs and symptoms of serotonin toxicity, see Clinical Features of Some Adverse Drug Interactions, Serotonin toxicity and serotonin syndrome... 

Ereshefsky L. Drug-drug interactions involving antidepressants focus on venlafaxine. J CUn Psychopharmacol 1996 (3 Suppl 2) 37S—50S. 

---