Well, being as I'm still here watching out for someone I might as well answer
Prozac has an official 'approximate' half life of "between 48 and 72 hours" (why the huge difference beats me!)
Taking a middle line of say 60 hours seems to be the easiest thing for calculation.
Half life is how long it takes HALF of whats in your body to leave.
The next half life takes HALF of whats left in your body to leave. (that would then be a quarter left).
Next half life takes HALF of that quarter to leave your body (leaving an eighth).
Next half life takes HALF of that eighth to leave your body (leaving one sixteenth).
Next half life takes HALF of that sixteenth to leave your body (leaving a ... um... 32 part of the original dose)
Final half life takes half of that remainder leaving a 64th negligible trace of the original dose).
So basically with a half life of 60 hours (which is 2 and a half days), on average you mutliply it by 6 for an estimate of it near enough leaving the body.
SO... 6 times x 2.5 days half life = 15 days?? before its left the body.
Is that right? I'm absolutely shattered and its hard to concentrate.
Going to the other extremes, 6 times a half life of 48 hours (2 days) = 12 days before its left the body.
Or 6 times 70 hours (approximately 3 days) = 18 days before its left the body.
If you're tthinking withdrawal symptoms, its possible for the REDUCTION to cause them - it doesn't have to be left entirely out of the body though thats more usual.
Hope that helps, and if the person I'm looking out for hasn't come back and need a bit more reassurance once I've posted this, then I'm off to bed