Selection of Antidepressants, Pt. 3

It occurs to me that in order to go any farther explaining how to
choose an antidepressant, I should take a moment to explain the concept
of an adequate trial.  Earlier, I mentioned that the
patient's history of response to previous antidepressant trials is one
of the most important factors to consider.  Having said that, it
is important to realize  that there are problems with that, both
practical and theoretical.



In order to derive valid conclusions from the outcome of any prior
trial on an antidepressant, it is necessary to have the right
information.

Having the right information means that you know what medication was
taken previously, at what dose, for how long; and to know what/if
anything good
happened, and what/if anything bad happened.  It is also necessary
to know what other medications were being taken at the same time, if
any.



In practical terms, hardly anyone keeps track of this, all that
systematically.  So if all you know is that a patients says "I
took Paxil before, and it didn't work," it does not really tell you
much.  But in actually practice, often that is all the information
you get.



So here we come to the idea of an adequate trial.  A trial on an
antidepressant is considered adequate, if the medication was taken at
an appropriate dose, consistently, for a sufficient
period of time, to determine whether or not that medication can be
helpful to the patient. 



What is an appropriate dose?  That depends.  Usually it is
the maximum dose, defined as either the highest dose that the patient
can or will tolerate, or the highest dose that the physician is willing
to prescribe.  Of course, when drugs are marketed, the FDA makes
the manufacturer declare a dose range for the drug.  But the
initial dosage ranges are almost always wrong.  And for various
annoying reasons, even when it is well-documented that they are wrong,
the package insert is not changed.  Sometimes you need to try
lower doses, in addition to trying higher doses. 



What constitutes a sufficient period of time?  Traditionally, we
have said six weeks.  But recent information suggests that the
traditional time frame may be incorrect.  That is one of the
lessons from the href="http://ajp.psychiatryonline.org/cgi/content/full/164/2/201">Star*D
study.

Longer times than expected were needed to reach response or
remission. In fact, one-third of those who ultimately responded did so
after 6 weeks (and half of those who ultimately remitted did so after 6
weeks). These results suggest that stopping a vigorously dosed
treatment for patients who report little benefit by 6 weeks is
ill-advised.

So this is still being worked out. 



The point is, that in order to make the best decisions about selection
of antidepressants, it is important to have good information.  It
is important to proceed methodically, employ good data collection, and
to keep track of all the data.