Dear , Thank you for your question and welcome to Just Answer. I am sorry that your husband is having such a bad abscess.Antibiotics alone will not cure your husband of his abscess. The source of the abscess, the infected tooth or gum, must be treated for him to get completely better. However, taking antibiotics alone should temporarily reduce the swelling and pain. Cephalexin is a very strong antibiotic but usually can take from 24 to 48 hours to begin to work on the infection. He has been taking it for about 48 hours now so hopefully he will get better later today. The antibiotic acts by corralling the infection causing it to localize into one area and "point" not unlike a pimple. Your comment that he wants to poke the abscess with a pin leads me to believe that the abscess might be at this pimple-looking stage, which is good. However, don't let him poke at the abscess. It's better if he starts rinsing the area with hot (as hot as he can stand without burning his mouth) salt water. Mix one half teaspoon salt in 8 ounces of hot water and rinse the solution over the abscess for two minutes every two hours. The heat will soften the wall of the abscess and cause it to burst, relieving the pressure of the infection.
You can certainly try the ER, but they won't do much unless there is a dentist on staff, which is very unusual for an ER. They will be able to prescribe a strong pain medication and might prescribe an additional antibiotic if the attending physician thinks the Cephalexin isn't working. If he has a particularly resistant bacteria causing the infection, we usually prescribe Flagyl along with the Cephalexin (2 antibiotics taken at the same time) to combat these kinds of infections.
I think if you can get the abscess to burst in the next hour of two with the hot salt water that should relieve the pain enough to ride out the weekend and then he needs to see his dentist on Monday. Otherwise, there is no shame in going to the ER. Just mention the additional antibiotic to the physician as they aren't always up to date on dental matters.
I hope this answers your question. If you would like to discuss this further or have any additional questions, please reply to my answer and I will get right back to you.
Sincerely, XXXXX XXXXX DDS