When does butt itching stop after taking the tablet (vermox)?

Don't scratch. The pinworms will die quickly. However, the problem with having an itchy butt is the "itch-scratch" cycle: you scratch, which makes you itch, which makes you scratch, and so on. The key is to leave your butt alone: don't scratch, don't overwipe, and don't wash with soap. Easier said than done, but it will get better.
Depends. The itch is triggered by a reaction to the glue like substance the pinworm lays its eggs in at your butt crack.You can calm it down with a mild steroid cream but recurrent scratching or vigorous wiping will aggravate it.As long as there is no more egg laying, the reaction will fade over a week or so.If your anal itch was due to something else treating pinworms will not stop it.