Which of the following medications is NOT a 3A4 substrate?

Clopidogrel is the correct answer because it is primarily metabolized by a different enzyme, namely CYP2C19, rather than CYP3A4. While some medications can undergo minor metabolism through multiple enzymes, clopidogrel's activation to its active form is predominantly facilitated by CYP2C19.

CYP3A4 is a significant enzyme in the metabolism of many drugs, and several of the other medications listed are indeed substrates of this enzyme. Warfarin, for example, has multiple metabolic pathways, but it can be influenced by CYP3A4 activity, which can affect its levels and efficacy. Gleevec (imatinib) is another example, as it is known to be a substrate of CYP3A4, meaning its metabolism and clearance can be affected by drugs that influence this enzyme. Fentanyl is also metabolized via CYP3A4, making it susceptible to interactions with other drugs that are inducers or inhibitors of this enzyme.

Thus, while many of the medications listed interact with CYP3A4 in some capacity, clopidogrel uniquely relies on CYP2C19, which sets it apart in the context of the question.