Response and effectiveness

Peak citalopram blood levels occur within 1 to 6 hours, with an average of 4 hours.

Initial improvements may be seen within 1 to 2 weeks; however, the maximum antidepressant effects may take up to 4-6 weeks of regular dosing.

Initial effects for anxiety disorders (such as generalized anxiety, obsessive compulsive disorder, panic disorder, and posttraumatic stress disorder) may be seen within two weeks, with ongoing improvements seen after four to six weeks.

Citalopram's effects last one to two days after a single dose. The half-life ranges from 24 to 48 hours (average 35 hours). With liver disease, the half-life doubles and increases by 30% to 50% in patients over the age of 60.