PrepTest 142, Section 1, Question 6
While grapefruit juice is a healthy drink, it(63 more words not shown)
Which one of the following,(7 more words not shown)
- AThe amount of(12 more words not shown)
- BGrapefruit juice is(11 more words not shown)
- CWhen scientists removed(15 more words not shown)
- DThe chemical in(17 more words not shown)
- ELong before the(18 more words not shown)
Reading the argument
My first thought is to warn patients about the juice. If it makes an ordinary dose act like a larger one, combining the two could be dangerous.
The author goes in another direction: deliberately use the juice to amplify a smaller dose. I can see how that might work if the amplification were dependable. Imagine giving one tenth as much medicine and knowing the juice would produce exactly the intended effect.
But what if it amplifies the medicine tenfold for one person and only twofold for another? Then the same plan could give different patients very different effective doses. The argument itself says getting the wrong dose is dangerous.
What we’re looking for
For a weakener, I'd look for a reason that this supposed precision is unreliable. Our prediction concerns different responses in different people; we'll need to see what kind of variability the answers actually give us.
Working the answers
- ACorrect
The variability is in the juice itself. A prescribed amount of juice doesn't supply a predictable amount of the chemical: one glass could contain much more than another. That makes the proposed way of controlling the medicine's effect unreliable. The plan meant to deliver a controlled effective dose using less medicine could instead leave someone with too much or too little. This undermines the recommendation for the same basic reason as our prediction, even though it locates the uncertainty in a different place.
- B
Lower cost doesn't show that the combination is a bad medical approach. If anything, it could be another attraction of reducing the amount of medicine. It doesn't address whether the resulting dose can be controlled safely.
- C
This supports the claim that the chemical affects absorption: remove it, and the effect disappears. But the argument already accepts that interaction. Confirming the effect doesn't expose a problem with using it deliberately to adjust a dose.
- D
Knowing the mechanism doesn't tell us that the proposed treatment is unsafe or unreliable. Inhibiting an enzyme explains how the chemical works; we still need a reason that using this effect would create a problem.
- E
Earlier advice to avoid juice suggests that doctors recognized a concerning interaction before identifying the chemical. It doesn't evaluate the new proposal to account for that interaction by lowering the dose. The history of a warning is less useful than A's specific reason the adjusted plan could be unreliable.
More Weaken questions
Learn the LSAT our way
Our platform drills Weaken questions at your level and adjusts as you improve.