I don't think Panadol will be a problem. (I also don't think it will help, but that's another discussion entirely ) If the painkiller were heavier duty ie codeine which converts to morphine in your body; doxylamine which is a muscle relaxant that causes drowsiness or an anti-inflammatory (nurofen, voltaren, aleve, ponstan, naprogesic etc) that can encourage bleeding if the skin is broken then I'd worry. Paracetamol generally has no effect on your mental alertness or ability to make decisions (obviously there is always going to be the odd person who reacts like that, but they are definitely the minority) so it shouldn't affect his/her mind at all.

Obviously I'll apply all the disclaimers here: don't use paracetamol if you have problems with your liver, if you have been drinking alcohol and don't take more than 4000mg of paracetamol per day at a dosage of 500-1000mg every 4-6 hours.