I am positive it's the Tussionex. I have taken this drug numerous times for Bronchitis and it always happens to me. I am in my late 40's and have had alot of surgeries in my life, because of cancer and so forth, and each time the Doctor's gave me pain med's after the surgery and when I got it for the flu and coughing also, the've all, including Tussionex, contained a drug that sedates your system, in other words relaxes you and your muscles don't want to contract. It's like a deading agent, if you know what I mean. It's happened to me alot in the past and I know that's the ONLY reason.
Probably due to not feeling well. Give yourself some much needed rest : )
Andi