Lexapro (escitalopram) is a selective serotonin reuptake inhibitor, commonly known as an SSRI. It belongs to one of the most widely prescribed classes of antidepressants and is FDA-approved for treating major depressive disorder and generalized anxiety disorder.
How SSRIs Work in the Brain
Your brain cells communicate using chemical messengers called neurotransmitters. Serotonin is one of these messengers, and it plays a key role in regulating mood, sleep, and anxiety. Normally, after serotonin delivers its signal between brain cells, it gets reabsorbed by the cell that released it. SSRIs like Lexapro block this reabsorption process, which leaves more serotonin available in the gap between cells. Over time, this increase in serotonin activity helps lift mood and reduce anxiety.
What sets Lexapro apart from other SSRIs is its precision. It targets the serotonin transporter (the protein responsible for reabsorbing serotonin) more selectively than most other drugs in its class. It is roughly 30 times more potent at this target than its close chemical relative, R-citalopram, and has minimal effects on other neurotransmitter systems. This selectivity is one reason it tends to cause fewer side effects than some older antidepressants.
Its Relationship to Celexa
Lexapro has an interesting chemical backstory. It is essentially a refined version of an older SSRI called Celexa (citalopram), which was approved in 1998. Citalopram is a mixture of two mirror-image molecules, called enantiomers. Only one of those molecules, the S-enantiomer, is responsible for the antidepressant effect. The other (R-citalopram) doesn’t contribute meaningfully to treatment and may even interfere with the active molecule’s work.
When Lexapro was approved in 2002, it contained only the active S-enantiomer. The goal was better tolerability and a cleaner pharmacological profile. In practice, this means Lexapro delivers the therapeutic punch of citalopram at a lower dose, with potentially fewer unwanted effects.
What Lexapro Is Prescribed For
The FDA has approved Lexapro for two conditions:
- Major depressive disorder (MDD) in adults and adolescents aged 12 and older
- Generalized anxiety disorder (GAD) in adults
Clinicians also prescribe it off-label for panic disorder, a use that has strong supporting evidence even though it lacks a formal FDA indication. Other off-label uses may include social anxiety and obsessive-compulsive disorder, though the evidence base varies.
How Long It Takes to Work
Lexapro raises serotonin levels within hours of taking it, but that doesn’t translate to immediate symptom relief. The brain needs time to adapt to the new chemical environment. Early signs that the medication is working, such as better sleep, more energy, or improved appetite, can appear within one to two weeks. The core symptoms of depression or anxiety, like persistent low mood or excessive worry, typically take six to eight weeks to fully improve.
This delay is common across all SSRIs, not just Lexapro. It’s one of the most important things to understand about this class of drugs: they require patience and consistent daily use before you can judge whether they’re effective.
Typical Dosing
Lexapro is taken once daily, with or without food. The standard starting dose for both depression and anxiety is 10 mg per day, which is also the recommended maintenance dose for most people. If needed, the dose can be increased to a maximum of 20 mg daily, though prescribers typically wait at least a week before making that adjustment. Older adults and people with liver conditions generally stay at 10 mg.
The drug is processed primarily by the liver and has a half-life of about 27 to 32 hours, meaning it takes roughly a day and a half for your body to clear half of each dose. This relatively long half-life is why once-daily dosing works and why, if you miss a single dose, blood levels don’t drop as dramatically as they would with a shorter-acting medication.
Common Side Effects
Like all SSRIs, Lexapro can cause side effects, particularly during the first few weeks as your body adjusts. The most frequently reported include nausea, trouble sleeping, drowsiness, increased sweating, and sexual side effects such as reduced libido or difficulty reaching orgasm. Many of these diminish over time. Nausea, for example, often fades within the first week or two.
Because Lexapro is more selective in its action than older antidepressants (and even some other SSRIs), it generally has a milder side effect profile. That said, individual responses vary widely. Some people tolerate it well from the start, while others need time to adjust or may ultimately do better on a different medication.
How It Compares to Other Drug Classes
SSRIs like Lexapro are one of several types of antidepressants. Others include SNRIs (which affect both serotonin and norepinephrine), tricyclic antidepressants, and MAOIs. SSRIs became the first-line treatment for depression and anxiety starting in the late 1980s because they are effective for most people and carry fewer serious risks than the older drug classes. Tricyclics and MAOIs, while still used in certain cases, tend to have more side effects and stricter dietary or drug interaction requirements.
Within the SSRI class itself, Lexapro is often considered one of the better-tolerated options due to its high selectivity for the serotonin transporter. Other SSRIs, like fluoxetine (Prozac) and sertraline (Zoloft), work through the same basic mechanism but differ in their potency, how long they stay in the body, and which side effects are most prominent. The choice between them usually comes down to individual response, side effect tolerance, and the specific condition being treated.