When is it safe to go back to work i have acute siatica i've had it for 1 week and its still painfull?

Not a question of : Safety but how you feel & what are you duties as well as commute. If your job needs you to be physical and very agile then it may be too soon but if it is an office type job it may be ok now as long as you can tolerate the commute. Again, use of medication that may affect your judgement, alertness & reaction time may play a role as well.

Not the issue: There is no safety issue, it is a quality of life issue. If you are experiencing leg pain, numbness & tingling; then at this time you should be taking an otc NSAID or prescription medication. Light stretching exercises should be started. Performing heavy labor, repetitive bending & lifting work should be avoided. Sedentary work with frequent breaks to stretch should be tolerated.

Probably Still Work: Generally most people can get relief from sciatic pain doing the conservative care within 3-6 weeks. If it persists after that, it can take up to 6 months to heal by itself. You may still be a candidate for epidural steroid injections that may help relieve the pain while your body heals itself. Most people can still work while they are healing from this with basic weight lifting restrictions.