What is the risk of taking gabapentin after the expiration date?

I got an old bottle of Gabapentin mixed up with my recently filled bottle, took pills that were 2 years expired for about 3 days and noticed that I didn’t sleep as well. But upon waking after that 3rd dose, my lips were swollen from the inside out, and my head kind of hurt. It took most of the day for the swollen lips to subside and the headache got worse throughout the day. The second day my lips just felt like I was extremely dehydrated. And the skin on my face looked a bit mottled. I also noticed that I felt hot and restless for a couple of days. I seriously do not recommend anyone doing this on purpose. A year old maybe, but not two!

there is no risk. I am taking some expired just to use them up

Out of date med's loose their strength.

Consult a pharmacist, I used to take them and the only thing I noticed is that they don't work as well. but that may be just me. A pharmacist would have a good idea as to the shelf life and the effects after it