No. Not if you want safe, sane and consensual anal sex. The anus should NEVER be numbed if you know what you are doing and don't want to HURT your partner.
Most do not recommend a numbing agent for anal sex. Anal sex needs to be prepared for and if it hurts... you're doing something wrong.
The problem with numbing agents is that the receiver could be hurt and not realize it. You don't want that, do you? If anal sex is done properly, it will NOT hurt.
My husband and I took a month or more to prepare for anal play. Starting with lube and a little finger just "rimming" the edge and taking our time and stopping if there was ANY pain.
You don't just "ram it in" with anal sex. You need a good NON-numbing lube and lots of preparation. I find I need to have at least one orgasm before we start anal sex, or I am not relaxed enough. We've been doing this for years, and I still need to be mentally and physically prepared. Small toys help some people prepare, but the most important thing is for the receiver to be relaxed and to WANT the anal sex.
No amount of numbing agent is going to make up for gentle and appropriate preparation, and she could end up getting hurt and not realizing it until later.