It wasnt strictly playing catch up, because I hadn't got behind and had no pain. I just substituted one for the other. The pain arrived within 5 minutes of taking them, then went away just as easily. Maybe they interfered with the codein? I've had a very weird afternoon, lots of urgent naps, then waking with a start, not quite knowing where I was. Hallucinations are listed in the potential side effects. I didn't have that beer either!! I'll not try them again.