The effect is most likely attributable to the average 30% lower creatinine clearance in women. No dose adjustment is required according to the product mono- graph or approval by regulatory agencies.394 396 Limited infor- mation is available among patients who participated in RELY with a body weight <50 kg.392 There were no differences in serum concentrations by sex for apixaban and rivaroxa- Finally, some questions remain regarding the incom- plete or scarce information on sex differences in the dosing of new oral anticoagulants. AF: Summary and Gaps AF is a major modifiable stroke risk factor, independently associated with a 4- to 5-fold increased risk of IS. AF is responsible for 1.5% to 25% of all IS depending on the age group. Anticoagulation is the most effective therapeutic strategy to decrease the risk of stroke. Risk stratification tools, such as CHA2 -VASc, are useful to stratify the risk of stroke and assist clinicians in the decision to initiate antico- agulation therapy. New oral anticoagulants are a useful alter- native to warfarin for the prevention of stroke and systemic thromboembolism; however, caution about overdosing must be used considering the additive effect of age, sex, renal func- tion, and concomitant medications (acetylsalicylic acid, clopi- dogrel, nonsteroidal anti-inflammatory drugs, P-glycoprotein inhibitors) in increasing the concentrations of new oral anticoagulants. Future research is needed to determine the appropriate dose of new oral anticoagulants in older women with a lower weight (eg, <50 kg) who are also exposed to other comor- bidities (eg, renal impairment) that influence the pharmaco- kinetics of these agents. In addition, none of the trials of new anticoagulants were powered to determine a sex difference in efficacy versus warfarin. AF: Recommendations 1. 