Me, biting your nails is just a bad habit. The problem is that you usually don’t realise that you’re doing it until it’d too late. This is what all the treatments are aimed at. You can use a bitter nail polish, put on false nails, wear gloves, whatever you need to do from biting your nails without you realising it. There are no drug needed (or available), just make sure you know you’re biting your nails as soon as you start. Good luck.