Today one of my patients asked a question about her medication, an SSRI, and my answers might be useful to others taking similar medication. She was taking fluoxetine, brand name Prozac, for a number of months. Even at a relatively high dose of fluoxetine, she continued to experience significant anxiety. Fluoxetine is ‘activating’ in some people, meaning that it sometimes increases the person’s sense of energy, which can, in turn, increase anxiety. At some point we decided to change to escitalopram, brand name Lexapro, a newer SSRI that has a high potency and somewhat less activation.
After two months, the anxiety seemed to be a little worse if anything; certainly not improved. Moreover the person felt that her mood had dropped somewhat since making the change. She called to ask if either fluoxetine or escitalopram are better for anxiety vs. depression, in consideration of changing back to fluoxetine, or to a different medication altogether.
Lexapro and fluoxetine are both SSRIs, i.e. they both essentially do the same thing. The same can be said for citalopram (which is virtually identical to Lexapro, generic name escitalopram), sertraline (Zoloft), and paroxetine (Paxil). They ALL block the transfer of serotonin back into nerve terminals after it has been released at the synapse. They ALL work in similar brain regions, on nerve terminals that release serotonin.
The individual differences between medications probably have more to do with misperception and placebo effects than true differences between the medications, with a few exceptions. Besides their SSRI effects, each medication has minor actions at other receptors— paroxetine’s actions at histamine receptors, for example, tend to increase appetite and cause drowsiness. Some of these extra actions are useful some are not. For example, fluoxetine tends to reduce appetite and boost energy in MOST, but not all people— effects that some people find desirable.
I don’t think there is much evidence that one SSRI is better for anxiety vs. depression or vice versa. In fact, I don’t think there is much evidence showing that one SSRI is better than another for any indication. People who do pharmaceutical studies tend to avoid head to head comparisons of medications, for reasons that I’m not entirely aware of. Maybe a company potentially funding a study would consider the stakes too high if the results favored the other medication. There are, again, some minor exceptions. Fluvoxamine is an older SSRI that has a reputation for treating OCD. But even in that case I think the reputation is a byproduct of rumor and expectation, rather than the result of scientific study.
I think of SSRI’s primarily as ‘anti-obsessing’ medications. They all have similar indications—for anxiety, OCD (which is a form of anxiety), panic attacks, and depression. Fluoxetine is indicated for premenstrual dysphoric disorder or ‘PMDD’, but I think most psychiatrists would say that any SSRI would work in a similar fashion for that condition.
Why do SSRIs treat depression? From what I can see, they reduce negative obsessing, negative rumination, obsessing over worry about perceptions by others… all ‘obsessive’ actions. I do not generally see a ‘lift’ in mood, as much as a letting go of negative thoughts, negative self-reflection, and worry.
Lexapro is a very potent SSRI; the most potent of all of the SSRIs. That doesn’t necessarily mean that it works better; it means that a similar effect requires a lower dosage, which may mean getting the desired therapeutic effects with fewer side effects from actions at other receptor sites.
To boost mood, psychiatrists commonly ‘augment’ SSRIs with different typse of medication. One common combination is an SSRI plus bupropion (Wellbutrin), the latter blocking reuptake of dopamine. Other combinations have been heavily marketed in recent years, such as adding Abilify or Seroquel, but those medications have wide-ranging effects at multiple receptor systems, and are generally reserved for fairly serious depression. They have significant risks and side effects compared to SSRIs and bupropion.
Let me know if I can answer any other questions for you. I do not think you would do significantly differently on a different SSRI, but I would not rule it out completely. One of the biggest mistakes that psychiatrists make is changing meds too frequently… but you have been on the Lexapro for some time, and a change back to fluoxetine would not be harmful. The actions are similar and so it is considered a ‘lateral move’, i.e. one where you would not be starting over, but rather moving to a different side effect profile.