It's based on the Norway study - they checked to see what difference banning it had made. The study only covered 3 years - hence the 36 months. I will look for the actual study.
It's mentioned here:
www.sciencemediacentre.org/expert-reaction-to-the-mhra-withdrawing-pholcodine-containing-cough-and-cold-medicines-from-the-uk-market-as-a-precautionary-measure/
Is it normal to talk to yourself?
Just had to put on a cardigan!


