Originally Posted by
panic_down_under
Yes, delaying the night dose to the next morning would be the best way of switching, however, whether this will make any difference to the insomnia issue is impossible to say.
When taken daily for a week citalopram plasma levels stabilize to a steady-state of around 2.5 times the peak from a single dose and then don't vary much across 24 hours. Therefore, in theory the time of day it is taken shouldn't make any difference, but in practice sometimes is does so switching to mornings might help.
Insomnia is a common SSRI side-effect, especially at the beginning. It is usually treated with small doses of a sedating antidepressant. Imho, the best for this is immediate-release trazodone (Desyrel), but apparently British GPs can't prescribe it for this purpose, so you will probably get mirtazapine (Remeron) instead. It is usually very effective, but as it has a long half-life the sedation may continue into the next day.