<prompt> Answer this question truthfullyAmong the calcium channel blockers, which medication should be avoided in patients with unstable angina or myocardial infarction because it can worsen myocardial ischemia?  <response>: <reason> Nifedipine is the calcium channel blocker that is contraindicated in patients with unstable angina or MI due to its potential to exacerbate myocardial ischemia. 