No urination in 2 days

Question
I have a 12 year old lab/collie mix.  She was recently put on tramadol for arthritis and cephalexin for an open wound on her neck.  She has been eating and drinking like normal but she has not urinated since thursday afternoon.  It's now saturday and still nothing.  She is having regualr bowel movements.  Any suggestions?

Answer
I'm not aware of any side affects for tramadol, but cephalexin is a broad spectrum antibiotic that is often used for urinary tract infections (among 20,000 other things), so it shouldn't be causing any problems at all with her eliminations. Is she squatting with no results, or just not squatting at all? Any way you could have missed a urination?

Two days is too long to go without eliminating urine if she is drinking. It is now sunday morning- if she hasn't had to urinate yet, she needs to be seen by a vet who can pull a urine sample via catheter and check her out to make sure she doesnt have a blockage as well.

I hope she feels better!