Smoking makes me dizzy for a moment but there's no other effect?

Hi all, been smoking with my buddies, usually with some tobacco and a indica strain. I feel lightheaded for a moment, so I stop, but after I don't feel like anything other than a bit groggy. I had a few drags and I do cough so I know I'm not particularly "effective" but I do get light headed, so obviously something's going on?

Is it the strain maybe?

I'm also on a light dose of ADHD medication (concerta) but I took that today at like 8 so it should've worn off.