Well I took one dose of the muscle relaxer I was prescribed today for my back pain and it worked great. But now it’s worn off and I’m in pain again and one of the side effects is urinary retention! I wrote a note to the doctor I saw today telling her this and that I’ve had urinary retention twice from psych meds and could she please write me a script for something else. I hope she replies tomorrow! Of course it has a long half life! I’ve read it builds up in your system. Glad I only took it once!