Lexapro is not a tricyclic antidepressant. It is a selective serotonin reuptake inhibitor (SSRI), a completely different class of medication. The two drug classes work differently in the brain, carry different side effect profiles, and pose different risks. Understanding the distinction matters if you’re comparing medications or trying to make sense of a prescription.
What Class Lexapro Actually Belongs To
Lexapro (escitalopram) is an SSRI, FDA-approved in 2002 for treating major depressive disorder in adults and adolescents 12 and older, and generalized anxiety disorder in adults and children 7 and older. It works by blocking the reabsorption of serotonin in the brain, which leaves more serotonin available to improve mood and reduce anxiety. It has minimal effects on two other brain chemicals, norepinephrine and dopamine, that some other antidepressants target.
Lexapro is actually a refined version of an older SSRI called Celexa (citalopram). Chemists isolated the more active half of the citalopram molecule to create escitalopram, with the goal of delivering the same benefit at a lower dose with fewer side effects.
How Tricyclic Antidepressants Differ
Tricyclic antidepressants (TCAs) are an older class of medication developed in the 1950s and 1960s. They increase levels of norepinephrine primarily, along with serotonin, but they do so in a much less targeted way than SSRIs. TCAs also block several other receptor systems in the body, which is why they tend to cause more side effects.
Common TCAs include amitriptyline (Elavil), nortriptyline (Pamelor), desipramine (Norpramin), and clomipramine (Anafranil). These medications are still prescribed today, often for chronic pain, nerve pain, migraines, and obsessive-compulsive disorder rather than as first-line depression treatment.
Side Effects: Why the Distinction Matters
The practical reason this classification matters is side effects. TCAs block receptors that affect many body systems beyond mood, leading to what doctors call anticholinergic effects: dry mouth, constipation, blurred vision, urinary retention, and drowsiness. They also carry a higher risk of cardiovascular side effects, including dangerous heart rhythm changes. In clinical studies, TCAs have been associated with higher dropout rates because patients find them harder to tolerate.
SSRIs like Lexapro were developed specifically to be more targeted. By focusing primarily on serotonin reuptake, they avoid many of the side effects that make TCAs difficult to take. That said, SSRIs have their own side effect profile, including nausea, sexual dysfunction, insomnia, and weight changes. Lexapro is not side-effect-free, but the overall burden tends to be lighter than with tricyclics.
Safety in Overdose
One of the most significant differences between these two classes is what happens in an overdose. TCAs are considerably more dangerous when taken in excess, with a higher risk of fatal heart rhythm problems and seizures. SSRIs are generally much safer in overdose than both TCAs and another older class called MAOIs. In 2023, SSRIs were mentioned in nearly 65,000 single-substance toxic exposures reported to U.S. poison centers, yet only 3 were fatal.
That said, escitalopram and its parent compound citalopram are considered potentially more toxic in overdose than some other SSRIs like sertraline or fluoxetine, largely due to their effects on heart rhythm at very high doses. This is a relative concern, though. They remain far safer than tricyclics in this regard.
What to Expect if You’re Starting Lexapro
If you’ve been prescribed Lexapro and were wondering whether it carries the same side effect burden as a tricyclic, the short answer is that it typically does not. Lexapro raises serotonin levels in the brain within hours, but you won’t feel the full therapeutic effect right away. Early signs that it’s working, like better sleep, more energy, or improved appetite, may appear within one to two weeks. Relief from core depression symptoms, such as persistent low mood or loss of interest in things you used to enjoy, can take six to eight weeks.
This slower timeline is normal for SSRIs and does not mean the medication isn’t working. It reflects the time your brain needs to adapt to the change in serotonin signaling, a process that is fundamentally different from how tricyclics interact with brain chemistry.