Key takeaways:
Clonazepam (Klonopin) is a benzodiazepine medication that can treat conditions such as seizures and panic disorder. It interacts with several medications and substances.
Key clonazepam interactions include opioids, antihistamines, and other medications that cause drowsiness. Combining them with clonazepam can lead to excessive drowsiness or potentially serious breathing issues.
Clonazepam also interacts with alcohol and cannabis. These substances can worsen clonazepam’s side effects, such as impaired coordination and drowsiness.
Clonazepam (Klonopin) is a benzodiazepine. It’s FDA approved to treat seizures and panic disorder. It’s also sometimes prescribed off-label to treat anxiety and alcohol withdrawal syndrome. Benzodiazepines like clonazepam work by slowing activity in the brain and nervous system.
Because of how it works, there’s a risk of serious side effects with clonazepam, such as excessive drowsiness or trouble breathing. And certain medications and substances can raise the risk of these complications. Below, we’ll review seven notable clonazepam interactions. But keep in mind these aren’t the only possible interactions.
1. Opioid pain relievers
Opioids are medications that are prescribed to treat moderate to severe pain. Common examples of opioids include tramadol, oxycodone, and morphine. Combining clonazepam with opioids can lead to excessive drowsiness and life-threatening breathing problems. In fact, clonazepam has a boxed warning (the FDA’s strictest medication warning) advising people to avoid this combination.
In most cases, healthcare providers would avoid prescribing opioids if you take clonazepam. But in cases where a person needs both, you should exercise caution. Ask your care team how much time should separate the doses of the medications. And be sure to report any excessive drowsiness to your provider right away.
2. Antihistamines
Antihistamines are medications that are commonly taken to treat seasonal allergies. But taking an antihistamine if you also take clonazepam could raise the risk of excessive drowsiness. The risks with this clonazepam interaction are higher with older antihistamines, such as diphenhydramine (Benadryl) and hydroxyzine (Vistaril).
Switching to a newer, non-drowsy antihistamine, such as fexofenadine (Allegra), is one option to help manage this interaction. Taking these antihistamines with clonazepam carries a much lower risk for excessive drowsiness.
You can also discuss other allergy medications with your provider or pharmacist. An option that doesn't interact with clonazepam is a nasal steroid spray, such as fluticasone propionate (Flonase).
It’s possible that your provider may recommend taking both clonazepam and an older antihistamine. If this is the case, avoid driving or performing other actions that require focus while taking them. And let your provider know if you’re experiencing too much drowsiness.
3. Sleep aids
Similar to the interactions above, combining clonazepam with other sleep aids can cause people to become overly drowsy.
Prescription sleep aids that interact with clonazepam include:
Melatonin receptor agonists, such as ramelteon (Rozerem)
Non-benzodiazepine sedative hypnotics (also called “z-drugs”), such as zolpidem (Ambien) and eszopiclone (Lunesta)
Orexin receptor antagonists, such as suvorexant (Belsomra) and daridorexant (Quviviq)
Some prescription sleep aids, such as zolpidem, have similar side effects to clonazepam. Taking both can worsen these effects, sometimes to a dangerous degree.
But these aren’t the only sleep medications that warrant caution with clonazepam. It’s also best to avoid over-the-counter sleep aids. Top examples include diphenhydramine (ZzzQuil), doxylamine (Unisom), and melatonin. Taking these with clonazepam can also cause more drowsiness than either would alone.
4. Other seizure medications
If you have a seizure condition, you might be taking more than one medication to help manage it. Examples of these medications include phenytoin (Dilantin, Phenytek) and carbamazepine (Tegretol). It’s important to know that clonazepam does interact with other seizure medications. But often, the benefits of the combination outweigh the risk of the interaction.
Many seizure medications can cause drowsiness, especially when you first start taking them. Taking more than one can worsen this side effect. Let your provider know if any sleepiness you experience is severe or greatly interferes with your routine.
In some cases, certain seizure medications, including carbamazepine and lamotrigine (Lamictal), can lower clonazepam levels in the body. This could make clonazepam less effective. Your provider may raise your clonazepam dosage to help manage this interaction.
What’s more, clonazepam can potentially affect levels of phenytoin. This could change how phenytoin works in your body. Your provider may want to check your phenytoin levels more often if you also take clonazepam.
5. Other medications that cause drowsiness
There are many other medications that can also make you sleepy. Like those detailed above, combining them with clonazepam can worsen this side effect. In some cases, it could lead to a dangerous amount of drowsiness.
Some medications that can make you feel more tired or drowsy include:
Muscle relaxers, such as cyclobenzaprine
Monoamine oxidase inhibitors (MAOIs), such as rasagiline (Azilect)
Tricyclic antidepressants, such as amitriptyline and nortriptyline (Pamelor)
Other antidepressants, such as trazodone
Beta blockers, such as metoprolol (Lopressor, Toprol XL) and propranolol
This isn’t a complete list. Your pharmacist can let you know if any of your medications cause drowsiness. Your healthcare provider should weigh the pros and cons of taking them with clonazepam. If they recommend the combination for you, discuss the best way to take them. They may recommend you separate medications or suggest dosage changes of one or both.
6. Alcohol
You should avoid drinking alcohol while taking clonazepam. Alcohol slows down the brain’s signals, at times causing slurred speech and unsteady movements. It affects some of the same areas of the brain as clonazepam. This can worsen the sedative effects of clonazepam. In some cases, mixing clonazepam and alcohol could lead to life-threatening breathing problems or raise the risk of overdose.
It’s important to be honest with your healthcare provider about how much alcohol you consume. This can help them keep you safe when prescribing medications. And if you’re trying to cut back on how much you drink, they can help you do so safely.
If you or someone you know struggles with substance use, help is available. Call the Substance Abuse and Mental Health Services Administration (SAMHSA) National Helpline at 1-800-662-4357 to learn about resources in your area.
7. Cannabis
There hasn’t been a lot of research on combining cannabis with clonazepam. But both cannabis and clonazepam can cause similar side effects, such as sleepiness and impaired coordination. So you may have a greater risk of experiencing these if taken together. Side effects may also be more intense.
It’s important to let your healthcare provider know if you consume cannabis while taking clonazepam. Being open about this can help them keep you safe.
When should I contact my healthcare provider about a clonazepam interaction?
Many of the above clonazepam interactions have the potential to be dangerous. It’s important that you and people you live with know how to recognize symptoms of a serious interaction. These can look similar to when a person takes too much clonazepam.
Serious symptoms include:
Confusion
Extreme drowsiness
Coordination problems
Unconsciousness
Slowed breathing
Make sure to call 911 right away if you notice these symptoms. Keep in mind a person experiencing them may not be able to call for help on their own. This situation can be life-threatening and requires immediate medical attention.
It’s best to share a complete medication list with your healthcare provider and pharmacist. This can help them look for and manage potential clonazepam interactions up front. Be sure to check in with your care team before starting clonazepam and anytime medication changes happen.
The bottom line
Common clonazepam interactions include opioids, antihistamines, and other medications that cause drowsiness. Alcohol and cannabis also interact. In many cases, clonazepam interactions raise the risk of serious side effects, such as slowed breathing or severe drowsiness. In some instances, this can be life-threatening. Have your healthcare provider and pharmacist review your current medication list to help identify clonazepam interactions.
Why trust our experts?
References
Bounds, C. G., et al. (2023). Benzodiazepines. StatPearls.
Bryant Ranch Prepack. (2023). Clonazepam [package insert].
Montoro, J., et al. (2013). H1 antihistamines and benzodiazepines. Pharmacological interactions and their impact on cerebral function. Journal of Investigational Allergology and Clinical Immunology.
National Alliance on Mental Illness. (2023). Clonazepam (klonopin).
Substance Abuse and Mental Health Services Administration. (2023). SAMHSA’s national helpline.
United States Drug Enforcement Administration. (n.d.). Benzodiazepines.
U.S. Food and Drug Administration. (2017). FDA Drug Safety Communication: FDA warns about serious risks and death when combining opioid pain or cough medicines with benzodiazepines; requires its strongest warning.
