Official Explanation
Weaken the pharmacist's argument
Since this is a weaken question, you'll want to identify the conclusion and the premise of this argument, and then weaken the link between them.
Conclusion: The pharmacist argues that he asks patients to revisit their doctors before prescribing compounded Certirizine to those patients in order to determine whether there may be any non-compounded alternatives.
Premises: The pharmacist does this because of unknown side effects associated with the compounded drug, as well as his desire to minimize health risks to the patient.
The assumption here is that the non-compounded alternatives have no such risk to patient health.
Answer choice (A) about allergies possibly leading to serious medical problems if left untreated does nothing to weaken this argument. While it may be the case that the delay in patient's receiving treatment could lead to problems, this answer choice doesn't weaken the connection between what the pharmacist does and his stated reasons for doing so. That connection is what you're actually trying to weaken in a weaken argument, not the conclusion itself, as this answer choice does.
Answer choice (B) about the drug's having unknown side effects in both compounded and non-compounded forms does weaken the argument. Since the pharmacist bases his recommendation about compounded Certirizine on the fact that there are unknown side effects, it would make no sense for the doctor not to make a similar recommendation for non-compunded Certirizine if in fact that form of the drug also has unknown side effects. This answer choice therefore weakens the pharmacist's argument and is the correct answer.
Answer choice (C) about the pharmacist's belief that the drug studies being not well-substantiated, does nothing to weaken this argument. Whether the studies are well-substantiated or not is outside the scope of the argument.
Answer choice (D) about the side effects of most medicines, is also outside the scope of the argument. You're not concerned with most medicines, only this one. And you have no information to determine whether this medicine is or isn't part of the "most" medicines with side effects not necessarily appearing for two years.
Answer choice (E) strengthens, not weakens the pharmacist's argument. The fact that the pharmacist can assess known risks, but not unknown risks, makes him more likely to refer patients to other doctors when prescribing this drug, which has unknown risks.
The correct answer is (B).
Weaken the patient's argument
Since this is a weaken question, you'll want to identify the conclusion and the premise of this argument, and then weaken the link between them.
Conclusion: The patient argues that there must be some other reason than unknown side effects that the pharmacist is asking him to see his own doctor before receiving a prescription for compounded Certirizine.
Premises: The patient makes this conclusion based on the fact that he has received prescriptions for compounded medicines previously and has never had to revisit his doctor before.
The assumption here is that this medicine is analogous to those other medicines. So to weaken this analogy, you're looking for the answer choice that indicates that this medicine is NOT similar to previous medicines.
Answer choice (A) about allergies possibly leading to serious medical problems if left untreated does nothing to weaken this argument, as it does not address the illogical connection between previous medicines and this one.
Answer choice (B) about the drug's having unknown side effects in both compounded and non-compounded forms does not weaken the argument, as it does not address the illogical connection between previous medicines and this one.
Answer choice (C) about the pharmacist's belief that the drug studies being not well-substantiated, does nothing to weaken this argument. Whether the studies are well-substantiated or not is outside the scope of the argument.
Answer choice (D) about the side effects of most medicines, is also outside the scope of the argument. You're not concerned with most medicines, only this one. And it does not address the illogical connection between previous medicines and this one..
Answer choice (E) weakens the patient's argument by describing a possible dissimilarity between this drug and other drugs. Perhaps all previous prescriptions of this patient were filled with drugs with known side effects. In this case, the patient's assertion that there is "some other reason" is weakened.
The correct answer is (E).