reducing anti depressants after three week

HI,

I just wondered if anyone knows how long it takes for anti depressants to leave you system? i have been on 50mg sertraline for 5 years and was fine up until about 3 months ago when i had an anxiety attack, it spiralled from there and i was suffering constantly. Anyway three weeks ago gp said i was to double my dose to 100mg, been okish up until this last week, and anxiety has gone sky high, to the point i was ringing the mental health team convinced i was going mad. I have now been told by gp that iam NOT and just suffering high anxiety as a side effect and to reduce my dose back to 50mg, he has also given me propranolol (spell) i can still feel the anxiety bubbling away and feel very very agigitated, cannot sit still at all. The one thing i forgot to ask gp was how long will it take for the extra 50mg to leave my system.

Thanks lynne