Answer to Question 1
A
Niacin causes a mild systemic inflammatory response with vasodilation that can result in the sensation of itching. This is not an allergy but can be very distressing to the patient. Often, taking aspirin reduces the inflammatory response and eliminates the itchiness. If the patient has no other health problems that would be worsened by aspirin, this should be tried first.
Answer to Question 2
D
The substances in grapefruit and grapefruit juice decrease the activity of the enzymes involved in the metabolism of modafinil. As a result, the drug blood level stays high longer, increasing the risk for side effects and adverse effects.