why does grapefruit juice potentials the effects of some medications while decrease the absorption of others?

Question

ie. grapefruit juice or extract amplifies the effects of some sleep meds (Dayvigo) while decreases the effects of others (Vyvanse)

In: Chemistry

Answer 1

If the drug is metabolized *out of* its active form by the liver enzymes that grapefruit components also occupy –> getting rid of active drug goes slower –> concentration stays higher for longer –> drug effect amplified.

If the drug is metabolized *into* its active form by those liver enzymes –> generating active drug goes slower –> concentration doesn’t reach as high as intended –> drug effect decreased.