Abstract
AIM: The aim of this study was to investigate the effects of co-medication with selective serotonin re-uptake inhibitors (SSRIs) on overanticoagulation during acenocoumarol maintenance treatment. METHODS: All subjects from The Rotterdam Study who received acenocoumarol maintenance treatment between April 1 1991 and September 9 2009 were followed for the event of an international normalized ratio (INR) >/=6, until death, end of treatment or end of the study period. With the Andersen-Gill extension of the Cox proportional hazards model, risks for repeated events of overanticoagulation in relation to concomitant SSRI use were calculated. RESULTS: The risk for overanticoagulation during acenocoumarol maintenance treatment was increased in combination with fluvoxamine (HR 2.63, 95% CI 1.49, 4.66) and venlafaxine (HR 2.19, 95% CI 1.21, 3.99). There was no increase in risk for the other SSRIs, but numbers of exposed cases were low for all SSRIs except paroxetine. CONCLUSION: Fluvoxamine and venlafaxine were associated with a more than double risk of INR values >/=6 in acenocoumarol treated subjects.
