Paxil vs Lexapro: Weight, Sleepiness, and Stopping Compared

Side effects are often what decide whether an antidepressant becomes part of your life or ends up in a drawer. Feeling foggy through every afternoon, watching the scale creep up, or feeling awful when you miss a day can outweigh the benefit, even when the medication is helping your mood. If you’re choosing between Paxil and Lexapro, those everyday realities deserve a real answer.

Both drugs keep more serotonin available by blocking its reuptake, but how each one behaves in your body differs. The Lexapro prescribing information describes escitalopram as highly selective, with no or very low affinity for histamine, muscarinic, and adrenergic receptors, and a 27-to-32-hour half-life. The Paxil prescribing information describes paroxetine as having a roughly 21-hour half-life, inactive metabolites, and levels that don’t rise in simple proportion to dose. Comparing them well takes precision about how those properties show up in the side effects you’d actually feel.

On effectiveness, both have a solid track record. A network meta-analysis of 522 trials found escitalopram and paroxetine were both among the more effective antidepressants in head-to-head comparisons. For generalized anxiety, Canadian anxiety guidelines list both as first-line options. The results are real, and the evidence is well established.

But effectiveness is only half of the decision, and at Siggy we believe side effects deserve the same weight as benefits when choosing a medication. Paxil and Lexapro have been compared directly in trials that tracked who stopped, why, and what they felt when coming off. That head-to-head data answers the same question as an efficacy chart, which medication fits you, with more precision about daily life. The clearest differences between these two show up in the tolerability data.

What This Page Covers

• What Head-to-Head Trials Show
• Weight Gain
• Sleepiness and Energy
• Which Is Harder to Stop?
• Other Differences That Matter
• How to Choose Between Them

What Head-to-Head Trials Show

The most useful comparison comes from a double-blind 24-week head-to-head trial of 121 people with generalized anxiety disorder, randomized to escitalopram (10 to 20 mg) or paroxetine (20 to 50 mg). Anxiety improved similarly in both groups, and the difference wasn’t statistically significant. Side effects told a different story:

Measure in the 24-Week Trial	Paxil (Paroxetine)	Lexapro (Escitalopram)
Stopped due to side effects	22.6%	6.6%
Insomnia	25.8%	14.8%
Constipation	14.5%	1.6%
Decreased libido	22.6%	4.9%
Anorgasmia	26.2%	5.9%
Ejaculation disorder	30.0%	14.8%
Diarrhea	8.1%	21.3%

The trial reported statistical significance for the difference in stopping due to side effects, and with 121 people, the individual side effect gaps are best read as a pattern. Lexapro wasn’t side effect free: diarrhea was more common on it.

Depression trials point the same way. In a severe depression trial of 459 people followed for 24 weeks, 8% on escitalopram and 16% on paroxetine stopped because of side effects, and remission reached 75% versus 67%. In a flexible-dose 27-week depression trial of 323 people, 34% dropped out of the paroxetine group versus 21% of the escitalopram group.

Weight Gain

Paroxetine has the stronger weight signal. In a 26-to-32-week randomized trial comparing it with fluoxetine and sertraline, paroxetine was linked to significant weight gain, and more people on it gained at least 7% of their body weight. The Paxil label also lists weight gain among its frequent less common events.

The Lexapro label says people on escitalopram in controlled trials didn’t differ from placebo in clinically important weight change. Those trials were mostly 8 weeks long, so they say less about the long haul. Our guide to Lexapro and weight gain covers what longer-term data suggest.

Sleepiness and Energy

Paxil tends to be more sedating. In its label’s depression trials, somnolence affected 23% of people versus 9% on placebo, and weakness or low energy affected 15% versus 6%. In the Lexapro label’s depression trials, somnolence affected 6% versus 2% on placebo.

In generalized anxiety trials, the gap narrows: somnolence affected 15% on Paxil versus 5% on placebo, and 13% on Lexapro versus 7%. These numbers come from separate trial programs, so they suggest a difference without proving one. The Lexapro label adds that 10 mg a day didn’t impair thinking or motor performance in a study of healthy volunteers.

If sleepiness is a concern, timing can help. The Paxil label recommends a morning dose, while Lexapro can be taken morning or evening.

Which Is Harder to Stop?

Paroxetine, in head-to-head data. The 27-week flexible-dose trial included a planned 1-to-2-week taper, and people coming off paroxetine had significantly more discontinuation symptoms than people coming off escitalopram. In a 12-week anxiety trial that stopped treatment at the end, people who stopped escitalopram 10 mg had fewer discontinuation effects than those who stopped paroxetine 20 mg.

That doesn’t mean Lexapro is easy to stop for everyone. A 2024 meta-analysis of 79 studies listed escitalopram among the antidepressants with more frequent discontinuation symptoms and paroxetine among those with more severe ones. The Lexapro label recommends a gradual taper, and it notes that if symptoms become intolerable, returning to the previous dose and tapering more slowly may help.

Our guides on Paxil withdrawal and how to taper off Lexapro cover each in detail.

Other Differences That Matter

A few practical differences can outweigh side effects for some people:

• Approved uses: Paxil is FDA-approved in adults for depression, OCD, panic disorder, social anxiety, generalized anxiety, and PTSD. Lexapro is approved for depression from age 12 and generalized anxiety from age 7.
• Pregnancy: The Paxil label warns that first-trimester exposure is associated with a less than 2-fold increase in cardiovascular malformations. The Lexapro label says available data haven’t established an increased risk of major birth defects.
• Drug interactions: Paroxetine strongly blocks the CYP2D6 liver enzyme, and its label advises considering another antidepressant for people taking tamoxifen. Escitalopram has a modest CYP2D6 effect, raising metoprolol exposure by 82% in one study.

In generalized anxiety specifically, the 12-week trial found escitalopram 10 mg more effective than paroxetine 20 mg, while paroxetine beat placebo only on some secondary measures.

How to Choose Between Them

These are considerations to discuss with your prescriber:

• Lexapro may fit better if weight, daytime sleepiness, or sexual side effects are major concerns, if you might want to stop later, or if pregnancy is possible.
• Paxil may fit better if you’ve done well on it before, or if you have panic disorder, social anxiety, OCD, or PTSD and your prescriber prefers a drug with that specific approval.
• Whichever you take, don’t stop suddenly. Both can cause discontinuation symptoms.

For how these two fit alongside sertraline, our comparison of Paxil vs Zoloft covers the missed-dose and taper differences in depth.

If you have thoughts of harming yourself, call or text 988. If you’re in immediate danger, call 911.

Side effects like sleepiness, weight change, or sexual problems are exactly the kind of thing people put up with quietly for months.

Paxil and Lexapro both work, but in head-to-head trials Lexapro was easier to stay on, with fewer people stopping because of side effects and fewer discontinuation symptoms when treatment ended. Paxil still has a place, especially for people who’ve responded to it or need its broader anxiety approvals. If you’re comparing the wider class, our look at SSRI medications compared walks through the options side by side.

Ready to take control of your mental health? Start your anonymous intake with Siggy and get your plan reviewed by a licensed prescriber.

This article is for education only and isn’t a substitute for personal medical advice. Talk with your own clinician before starting, changing, or stopping any medication.