Chronic use of acetaminophen may increase the risk of what when administered with warfarin?

Chronic use of acetaminophen, especially at higher doses, can increase the risk of bleeding when administered with warfarin due to multiple mechanisms. Acetaminophen has been shown to affect liver metabolism, which is critical for the metabolism of warfarin. As warfarin is primarily processed in the liver, any interaction that alters this metabolic process can lead to changes in the effectiveness of warfarin, resulting in either increased or decreased anticoagulant effects.

When acetaminophen is used chronically, it may inhibit the enzymes responsible for warfarin metabolism, leading to elevated levels of warfarin in the bloodstream. This elevation can enhance warfarin's anticoagulant effects, consequently increasing the risk of bleeding since warfarin works by inhibiting the clotting factors in the blood. Therefore, the combination of chronic acetaminophen use and warfarin requires careful monitoring due to this heightened risk of bleeding, such as gastrointestinal hemorrhage or excessive bruising.

Other options, such as infection or nausea, are not directly associated with the interaction between acetaminophen and warfarin, nor does acetaminophen use correlate with an increased risk of constipation in this scenario.