Klonopin (clonazepam) is a prescription oral tablet used to treat certain anxiety and seizure disorders. Klonopin can cause side effects that range from mild to serious. Examples include drowsiness and dizziness.

Specifically, Klonopin is used to treat:

Keep reading to learn about the common, mild, and serious side effects that Klonopin can cause. For a general overview of the drug, including details about its uses, see this article.

Klonopin has boxed warnings. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Side effects explained” section.

Some people may experience mild to serious side effects during their Klonopin treatment. Examples of the drug’s commonly reported side effects include:

  • drowsiness
  • dizziness or unsteadiness
  • difficulty with coordination, such as when walking or bending to pick something up

Mild side effects have been reported with Klonopin. These include:

  • sexual problems, such as erectile dysfunction and reduced libido (sex drive)
  • headache
  • drowsiness
  • feeling dizzy or unsteady
  • difficulty with coordination
  • problems with thinking or memory
  • increased production of saliva
  • fatigue
  • slurred speech
  • nervousness
  • muscle pain or weakness
  • constipation
  • unexpected weight gain

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bothersome, talk with your doctor or pharmacist. And do not stop taking Klonopin unless your doctor recommends it.

Klonopin may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

Serious side effects have been reported with Klonopin. These include:

  • sleepiness, difficulty with thinking or judgment, and slowed reaction times that can make certain activities dangerous, such as driving
  • respiratory depression (slow, shallow breathing)
  • changes in mood or behavior, such as depression or irritability
  • suicidal thoughts and actions
  • new or worsening seizures
  • boxed warnings: risk of misuse and addiction, dependence and withdrawal, and serious side effects or death if used with opioids*

If you develop serious side effects while taking Klonopin, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

* To learn more about these side effects, see the “Side effects explained” section.

Note: After the FDA approves a drug, it tracks and reviews the side effects of the medication. If you’d like to notify the FDA about a side effect you’ve had with Klonopin, visit MedWatch.

Allergic reaction

For some people, Klonopin can cause an allergic reaction. In general, symptoms of allergic reaction can be mild or serious.

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest a treatment to manage your symptoms and can determine whether you should keep taking Klonopin.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms you’ve had a serious allergic reaction to Klonopin, they may have you switch to a different treatment.

Get answers to some frequently asked questions about Klonopin’s side effects.

Can Klonopin cause long-term side effects?

It’s possible. Examples of long-term side effects reported in studies of Klonopin include:

  • changes in mood or behavior, such as depression or irritability
  • suicidal thoughts and actions
  • misuse and addiction*
  • dependence and withdrawal symptoms*

To learn more about possible side effects of Klonopin and how long they may last, talk with your doctor.

* Klonopin has a boxed warning about this side effect. For more information, see the “Side effects explained” section.

Does Klonopin cause certain side effects in females?

Yes, it can. For example, Klonopin has been reported to cause the following side effects in some females:

To learn more about the side effects of Klonopin that occur specifically in females, talk with your doctor.

Note: In this article, we use the term “female” to refer to someone’s sex assigned at birth. For information about the difference between sex and gender, see this article.

Are older adults more likely to have side effects from Klonopin?

Klonopin causes similar side effects in older adults (ages 65 years and older) and younger adults. However, older adults are more likely to have medical conditions, such as liver or kidney problems, that can raise the risk of side effects with Klonopin.

Certain side effects that may be more common in older adults taking Klonopin include:

  • confusion
  • sleepiness
  • dizziness
  • unsteadiness

These side effects can increase the risk of falls in older adults. For these reasons, doctors typically prescribe lower doses of Klonopin for older adults.

To learn more about Klonopin’s side effects in older adults, talk with your doctor or pharmacist.

Learn more about some of the side effects Klonopin may cause.

Misuse and addiction

Klonopin has a boxed warning about the risk of misuse and addiction. A boxed warning is the most serious warning from the FDA.

Misuse refers to taking a drug in a way other than how a doctor prescribes it. Examples of misuse include using the drug more often or at higher doses than recommended by your doctor.

Misuse increases the risk of overdose, which can lead to trouble breathing, coma, and even death. It can also lead to addiction. With addiction, you feel unable to stop using the drug, even if it’s causing harm.

Addiction may cause symptoms such as:

  • craving the drug
  • hiding the use of the drug from others
  • prioritizing the use of the drug over other activities
  • going out of your way to get supplies of the drug

If you’ve misused drugs or alcohol in the past, your risk of misuse or addiction with Klonopin may be higher.

What might help

To reduce the risk of misuse and addiction, your doctor will likely prescribe the smallest possible amount of Klonopin for the shortest possible time.

You should take Klonopin only as your doctor has prescribed. If you have any symptoms of addiction while taking the drug, talk with your doctor right away.

If you have questions or concerns about the risk of misuse or addiction with Klonopin, talk with your doctor or pharmacist.

Dependence and withdrawal

Klonopin has a boxed warning about the risk of dependence and withdrawal.

Taking Klonopin can lead to physical dependence. This condition occurs when your body relies on a drug to function as usual.

If you suddenly stop taking Klonopin, you may experience withdrawal symptoms. (These are side effects that can occur when you stop taking a drug that your body has become dependent on). Examples of withdrawal symptoms include:

In some cases, withdrawal symptoms from Klonopin can last for weeks or even months.

Factors that can increase the risk of withdrawal symptoms when stopping Klonopin include taking the drug in high doses or for long periods of time.

What might help

Before you end your Klonopin treatment, your doctor will likely lower your dosage slowly over time. This can help reduce your risk of withdrawal symptoms after you stop taking it.

If you have withdrawal symptoms after you’ve ended your Klonopin treatment, talk with your doctor. They can recommend ways to ease these symptoms.

If you have questions or concerns about the risk of dependence or withdrawal from Klonopin, talk with your doctor or pharmacist.

Serious side effects or death if used with opioids

Klonopin has a boxed warning about the risk of serious side effects or death if used with opioids.

Opioids are powerful pain relievers. Examples include oxycodone (Oxycontin), hydrocodone (Hysingla ER), and tramadol (Conzip, Ultram). Taking Klonopin with an opioid can cause serious side effects that can be life threatening. Examples include:

What might help

Your doctor will usually avoid prescribing Klonopin with an opioid unless there are no safer alternatives.

If you take Klonopin with an opioid, be sure to take the drugs only as prescribed by your doctor. Do not take a higher dose of either drug than your doctor recommends.

If you do take these drugs together, you should tell people you live with, a caregiver, or others who you see regularly so they can help watch for serious side effects. If you become very sleepy or your breathing becomes slow and shallow, you or another person should call your doctor right away. If you become unresponsive or stop breathing, another person should call 911 or your local emergency number.

Keeping track of side effects

During your Klonopin treatment, consider taking notes on any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking a new drug or using a combination of treatments.

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what other medications you were taking
  • any other information you feel is important

Sharing notes with your doctor will help them learn more about how Klonopin affects you. They can then use this information to adjust your treatment plan if needed.

Below is important information you should consider before taking Klonopin.

Boxed warnings

Klonopin has boxed warnings. A boxed warning is the most serious warning from the FDA. For details, see the “Side effects explained” section.

Other warnings

Klonopin can sometimes cause harmful effects in people who have certain conditions. This is known as a drug-condition interaction. Other factors may also affect whether Klonopin is a good treatment option for you.

Talk with your doctor about your health history before you take Klonopin. Be sure to tell them if any of the following factors apply to you:

Help is out there

If you or someone you know is in crisis and considering suicide or self-harm, please seek support:

If you’re calling on behalf of someone else, stay with them until help arrives. You may remove weapons or substances that can cause harm if you can do so safely.

If you are not in the same household, stay on the phone with them until help arrives.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.