Which antihypertensive agent may yield a positive screening result on a urine immunoassay for opiates?

The antihypertensive agent that may yield a positive screening result on a urine immunoassay for opiates is verapamil. This medication is a calcium channel blocker that can share structural similarities with certain opiate compounds, leading to potential cross-reactivity in urine drug screening tests. While the primary purpose of verapamil is to manage hypertension and certain types of angina, its chemical structure can inadvertently trigger a false positive result for opioids on drug tests.

In contrast, amlodipine, lisinopril, and metoprolol do not have the same structural similarities with opiates and are less likely to interfere with drug screening assays, making them less relevant to this specific question. Thus, verapamil's potential for cross-reactivity is the key reason it could yield a positive result in urine immunoassays for opiates.