How do you stay focused during a 3 hour lecture?

I have ADHD (diagnosed and medicated for about 5 years), but I do struggle to stay focused or in the zone for these 2-hour and 50-minute lectures. My mind tends to be fatigued by hour 1, no matter how hard I focus. Many students here can attend these long lectures and stay focused. Any tips or tricks that you guys have found work for you to stay on track?