There are specific differences in pharmacokinetics which may help in choosing an agent. Below is a comparison of a list of selected pharmacokinetic parameters of the four most commonly used SSRIs.

Parameter
Fluoxetine
 Fluvoxamine Paroxetine
Sertraline
(HalfLife) Tl/2 24-72 hours (parent drug) 7-15 days (metabolite) 15 hours 21 hours 26 hours (parent drug) 66 hours (metabolite)
Active metabolites Norfluoxetine none none
Desmethylsertraline
Usual dose 20-80mg/day 50-300mg/day 10-50mg/day
50-200mg/day