Answer to Question 1
D
Colestipol can change the action of the anticoagulant warfarin in two ways. They can decrease the absorption of vitamin K, which would intensify the effects of warfarin and increase the risk for bleeding (as evidenced by a high INR). Bile acid sequestrants can also directly bind warfarin in the intestinal tract and cause its rapid elimination. This action would inactivate warfarin activ-ity and increase the risk for clot formation (as evidenced by an INR level that is lower than the therapeutic range). Although all of the above laboratory blood values can help diagnose a bleed-ing problem, the most sensitive test is the INR.
Answer to Question 2
A
Although the drug oxybate induces a deep sleep, it is used to prevent or treat narcolepsy. The mechanism is to ensure the person obtains adequate sleep during the night to prevent daytime sleepiness rather than directly causing brain stimulation for wakefulness.