Basically the same considerations described above relative to the tricyclics should be followed when prescribing an SSRI. Of interest is the relative confusion regarding therapeutic dose. Some patients respond well at relatively low doses and other require higher doses. How then do we determine that the patient has had an adequate trial before assuming they have a treatment refractory depression? Therapeutic drug monitoring (ie. Checking a blood level) is not available for SSRIs in general. Instead the clinician escalates the dose until dose limiting side effects appear or until response is noted.

It is instructive to consider the experience in general practice. One way to do this is to look at prescription records for a large number of patients and compare the doses initiated with how many remained on the medication for 4-6 months. The assumption is that if the doseis ineffective or intolerable the clinician will either raise the dose or stop the medication. This naturalistic experiment has been done with medicaid populations in California and Texas. The results are rather remarkable. About 90% of patients started on fluoxetine at 20mg/day remained on this dose at 6 month. On the other hand only about 25% of patients started on sertraline at 50mg/day (which is suggested as a therapeutic dose) remained on that dose for the entire 6 months. Frequently patients were switched to another antidepressant without the benefit of a trial of higher doses.

The implication is that a large number of clinicians do not feel comfortable titrating the sertraline. This creates a situation of prolonging the treatment trial in many patients. It would probably be better to start off with a drug and quickly titrate to a dose which is most likely to achieve remission.