Venlafaxine Warfarin

Clinically important, potentially hazardous interactions with aspirin, celecoxib, citalopram, etoricoxib, fluoxetine, NSAIDs, paroxetine, venlafaxine, warfarin... 

C9H(,03 1076-38-6) see Acenocoumarol Ethyl biscoumacetate Tioclomarol Warfarin Zonisamide a-(l-hydroxycyclohexyl)-4-methoxybenzeneacetonitrile (C15H19NO2 93413-76-4) see Venlafaxine (45)-3-[[(lS,2R)-2-hydroxy-3-cyclopenten-l-yl]carbonyl]-... 

Drugs that may affect trazodone include carbamazepine, phenothiazines, and venlafaxine. Drugs that may be affected by trazodone include alcohol, barbiturates, CNS depressants, digoxin, MAOIs, phenytoin, and warfarin. 

Drugs that may affect venlafaxine include cimetidine, cyproheptadine, and MAOIs. Drugs that may be affected by venlafaxine include clozapine, desipramine, haloperidol, indinavir, St. John s wort, trazodone, sibutramine, sumatriptan, and warfarin. 

Fluvoxamine inhibits liver drug-metabolizing enzymes. Dosages of alprazolam, theophylline, and warfarin must be reduced if any of these drugs are given concomitantly with fluvoxamine. Nefazodone may also decrease the metabolism of benzodiazepines, and venlafaxine may inhibit haloperidol metabolism. The answer is (B). 

In at least six cases venlafaxine appears to have increased the INRs and caused bleeding in patients taking warfarin. A similar case has been seen with duloxetine and warfarin. 

The possible interactions of warfarin or other antieoagulants with venlafaxine do not appear to have been studied, but, as of May 2000, the manufacturers had on record 6 case reports of increased prothrombin times, raised INRs and bleeding (haematuria, gastrointestinal bleeding, melaena, haemarthrosis) in patients taking warfarin with venlafaxine. ... 

No interaction is established, and the general relevance of these unpublished cases is uncertain. If one subscribes to the view that increased monitoring is necessary when any drug is started or stopped in a patient on warfarin or related drugs, then it would be prudent to monitor prothrombin times with venlafaxine. More study is needed. 

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