So, I drank a small bottle of robitussin earlier today. I have a rather bad cough, and nothing else worked, so we decided that since I was gonna see a movie, I didn't want to cough through the whole thing, so we'd buy a bottle of cough syrup and see if it helped. It did. It was a 100 ml bottle, and with 15 mg of DXM per 5ml, that adds up to enough DXM (300 mg) to get me decently stoned.
No visual distortions, but a definite stoned that lasted for around 5 hours, start to finish. However, I wouldn't suggest watching a movie, especially one that require much thinking or following a deep plot. I watched Public Enemies with a couple friends, and I could, re-watch the movie right now and learn things I missed. I had some pretty severe tunnel vision, which made reading hard, and I believe that my hearing was a bit bad, thanks to it for a while, because talking after the movie, I noticed a distinct diminishing in hearing.
And coming down from it was awesome. I felt sorta light headed. In fact, my whole body felt light, and I felt like I had tons of energy.
I'm definitely gonna have to do this again.