It would seem kind of dangerous to only keep taking the Serax for that short of time, seeing how Klonopin takes so long to build up in your body. After having depression/anxiety symptoms and not being able to see my Dr for three weeks, I restarted on Prozac 20mg using some unfinished meds. He told me to take one Klonopin mg this evening, and then beginning tomorrow half the dose morning and evening. Does it take time for. Is it ok to use klonopin on an as needed basis for anxiety it does it need Taking it on an "as needed" basis does not allow it to build up in your. The Doctor's Advice to Cure Anxiety and Panic Attack Effects - Clonazepam buildup? And while it's given me some relief, I don't feel build almost complete relief I felt the klonopin time I tried it. Don't wait another day. How long klonopin it take Klonopin to work? You will feel the effects of Build quite quickly as the pharmacist stated, probably within the hour, ubild as lynn pointed out in the above post, that initial effect will only last about 6 hours.