I know this is an old post but I tried the Lidocaine(Xylocaine) for rectal pain after BM. Unfortunately it didn't work for me. What did work was Indomethacin suppositories. They come in 50mg and 100mg doses. 50mg last about 4-5 hours for me(240 lbs) which is as long as I need for the pain to settle down. Indomethacin is an NSAID and didn't cause constipation like the opioid based drugs did for me. The medication kicked in fairly quickly too, 10-15 mins.
male - 53
Oct 29, 2015 DX anal adenocarcinoma; Stage I, T2, N0, M0 (my est)
Nov 18,2015 - Dr. changed prognosis to rectal adenocarcinoma
Dec 3, 2015 -After CT and MRI staging estimated to be from Stage 2a, T3N0M0 to Stage 3b, T3N1M0
Seeing Chemo/Radiologist Onc's Dec8-9, Surgeon Dec 14; Treatment TBD