"I was misinformed"

I was admitted to Ward 7 at Doncaster Royal Infirmary earlier this month for a shoulder replacement. I was not told by the doctor that after surgery I would put on Voltarol 50mg tablets, 1x3 times a day for my pain. For 18 months I have been taking paracetemol tablets 2x4 times a day. I needed them for the sever pain I was having with my shoulders. I was given both tablets whilst in hospital. During my last day in hospital I did ask what the red tablet (Voltarol) was for. What I cannot understand is why I wasn't told that there was no need for me to take the paracetemol tablets after my surgery. I took the paracetemol and Voltarol for another eight days after I came home before I realised what I was taking.