10 Paroxetine (Paxil) Side Effects You Should Know About

Paroxetine (Paxil) is an antidepressant medication. It belongs to a drug class known as selective serotonin reuptake inhibitors (SSRIs). Paroxetine was first approved in 1992 to treat depression. Since then it’s been approved for other conditions, including different anxiety disorders. A lower-dose version (Brisdelle) is used to treat hot flashes during menopause.

Paroxetine is thought to work by boosting the amount of serotonin in your brain. Serotonin is a chemical involved in regulating mood. Compared to other SSRIs, paroxetine has the most potent effect on serotonin. But this potency sometimes comes with some side effects.

Paroxetine side effects at a glance

Many paroxetine side effects are relatively mild and get better over time. More serious side effects are possible but less common.

Common or mild paroxetine side effects, many of which start in the first week of treatment, can include:

• Weakness

• Constipation

• Nausea

• Reduced appetite

• Diarrhea

• Dizziness

• Dry mouth

• Sexual problems

• Insomnia

• Weight gain

• Nervousness

• Drowsiness

• Sweating

• Tremor

• Yawning

• Urination problems

Less common but potentially serious paroxetine side effects include:

• Serotonin syndrome

• Antidepressant discontinuation syndrome

• Increased risk of bleeding

• Low sodium levels

• Serious allergic reactions

• Suicidal thoughts and behaviors

• Seizures

Keep in mind that while these side effects are possible, they may not happen to you. 

Here, we'll cover what you should know about 10 notable paroxetine side effects and how to manage them.

1. Nausea

Nausea is a common side effect of antidepressants — including paroxetine. Up to 1 in 4 people taking paroxetine during clinical trials reported nausea. And it’s more likely to happen with higher doses. But for many people, nausea usually improves over time as your body adjusts to the medication. 

Paroxetine can be taken with or without food. If you’re feeling nauseous after your dose, try taking it with food. Temporarily eating smaller meals and bland foods may also help while you’re feeling nauseous. 

If your nausea is interfering with your daily life or doesn’t go away, talk to your prescriber. They can help you lower your dose or switch you to a different medication. For example, extended-release (ER) paroxetine may cause less nausea for some people.

2. Drowsiness

It’s not unusual for antidepressants to make you feel drowsy. And among the different SSRIs, paroxetine seems to cause the most drowsiness. But this usually goes away after a few weeks of taking the medication.

Avoid driving or doing other tasks that require you to be alert until you see how paroxetine affects you. Let your prescriber know if your drowsiness doesn’t go away or gets worse. They may switch you to a different medication that’s less likely to make you drowsy.

3. Sleeping problems

Besides regulating mood, serotonin can also affect the areas of your brain that influence sleep. So, it may come as no surprise that paroxetine can cause sleeping problems for some people. For example, you may have a harder time falling or staying asleep.

If you’re having trouble sleeping after starting paroxetine, ask your prescriber or pharmacist about taking your dose in the morning instead of the evening.

4. Sexual problems

Many people taking SSRIs experience sexual problems. Paroxetine sexual side effects may include:

• Lower libido (sex drive)

• Trouble having an orgasm

• Delay in ejaculation

Paroxetine tends to have the highest rate of sexual problems among all SSRIs. Sometimes, this goes away after a few weeks. But this isn’t always the case.

One theory that this happens is that serotonin can affect hormones and chemicals involved in sexual arousal and orgasm.

Talk to your prescriber if sexual side effects don’t go away or become an issue at any point. They may add another medication to help limit these side effects. Or they may help you switch to an antidepressant that’s less likely to cause problems.

5. Weakness

Paroxetine can cause weakness, which may get better over time. But it can also be a sign of something more serious, including low sodium levels in your blood (called hyponatremia). 

Older adults and people taking diuretics (water pills) have a higher risk of hyponatremia. And it tends to happen within the first 2 to 4 weeks of starting the medication.

Hyponatremia can be serious. If you develop weakness, let your healthcare team know if it’s accompanied by headache, confusion, or feeling unsteady. This could be a sign your sodium levels are too low.

6. Weight gain

Studies suggest that paroxetine generally causes more weight gain than other SSRIs. But whether or not you gain weight — and how much you gain — varies by person. Weight gain is more likely to happen with higher doses or if you’re taking paroxetine for longer than 6 months.

If you’re concerned about gaining weight while taking paroxetine, talk to your healthcare team. They can give you tips for how to maintain your body weight and prevent possible fluctuations. This may include tracking your body weight and incorporating regular exercise into your routine.

7. Higher risk of bleeding

SSRIs like paroxetine can possibly raise the risk of bleeding. This risk may be higher if you’re taking paroxetine with other medications that also have bleeding risks. Examples include nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin), and blood thinners, such as warfarin (Coumadin, Jantoven).

Let your healthcare team know right away if you notice any new or unusual bruising, small purple or red spots on your skin, or other signs of bleeding.

8. Serotonin syndrome

Serotonin syndrome can happen when serotonin levels rise too high in your body. This isn’t common with paroxetine and other SSRIs, but severe cases can be life-threatening. Serotonin syndrome from paroxetine is more likely to happen if you’re taking higher doses or if you’re taking it with other medications or supplements that increase serotonin. 

Mild symptoms include sweating, fast heart rate, and tremor (mild shaking in hands). More serious symptoms include uncontrollable body movements, confusion, and high fever. Let your prescriber know if you develop mild symptoms. If they become severe, call 911 or get emergency medical help right away. 

Also, make sure your prescriber and pharmacist have your current medication list. They can check for medications that could raise the risk of serotonin syndrome.

9. Antidepressant discontinuation syndrome

Don’t suddenly stop taking paroxetine — or lower your dose too quickly — on your own. You may start experiencing symptoms such as headache, dizziness, and nausea. This is called antidepressant discontinuation syndrome. And it’s thought to be due to a sudden drop in serotonin.

Antidepressant discontinuation syndrome is temporary, but it can be unpleasant. To avoid it, don’t stop taking paroxetine or lower your dose without talking to your prescriber. They can help you safely — and slowly — taper off the medication.

10. Suicidal thoughts and behaviors

Paroxetine has a boxed warning (the FDA’s strictest medication warning) about the risk of suicidal thoughts and behaviors. This risk appears to be highest in people under 25 years old. All antidepressants carry this warning.

Everyone taking antidepressants should keep an eye out for suicidal thoughts and behaviors. This is especially the case after starting treatment and after dosage changes. Let your healthcare team know right away if you notice changes in your mood or behavior.

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Written by:

Sandy P. Bonfin, PharmD, BCPS

Sandy Bonfin, PharmD, BCPS, is a clinical pharmacist at a Florida hospital. Bonfin has worked in pediatric medicine, emergency medicine, internal medicine, and intensive care.

Edited by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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