While grapefruit juice is a healthy drink, it has been discovered that a chemical in the juice affects how certain me...

shunhe on July 6, 2020

Hi @Ame15,

Thanks for the question! So let’s recap this question real quick. We’re told that while grapefruit juice is healthy, a chemical in it can affect how certain medicines are absorbed and basically makes medicines stronger. And getting the wrong dose is dangerous. So since you should always have the lowest effective dose, you should take lower doses of the medicines with prescribed amount of grapefruit juice (since that’ll make the medicines more potent basically).

OK, now we’re asked for something that’ll weaken this argument. Now take a look at (A), which says that the amount of the chemical in the grapefruit juice is highly unpredictable from glass to glass. Well, if this is true, then prescribing a certain amount of grapefruit juice means that we still don’t know how much chemical you take. And it’s the chemical that affects how the medicines are absorbed. You could pour one glass and get almost no chemical (and, reasonably, less effect), and pour another of the same amount and get a ton of chemical. So this would show that this method of prescribing an amount of grapefruit juice with your medicine is unreliable, and thus weakens the argument. So (A) is correct.

(E), on the other hand, just talks about what some doctors used to do, but doesn’t weaken the practice as suggested right now, which is based on newer information.

Hope this helps! Feel free to ask any other questions that you might have.