Having trouble falling asleep can be stressful. Around 20 percent of adults take some form of over-the-counter sleep medication to help them fall asleep.
Antihistamines, while typically associated with allergies, are frequently used for sleep problems.
In this article, we’ll explore hydroxyzine, a prescription antihistamine that may help with insomnia.
We will also cover side effects, dosages, drug interactions, and how to know when you should see a doctor.
Hydroxyzine for Sleep
Over-the-counter sleep aids are one of the most popular at-home medicines that people use.
These include medications like Aleve PM, Nyquil, Tylenol PM, Unisom, and Benadryl.
Hydroxyzine is a prescription-only antihistamine that is in the same family as diphenhydramine (Benadryl).
The use of hydroxyzine is also FDA-approved for allergic skin reactions and is used as a sedative prior to general anesthesia.
Hydroxyzine is not approved by the Food and Drug Administration for treating insomnia.
However, many healthcare providers do prescribe it for sleep problems. This is known as off-label use.
It works on two brain chemicals: histamine and serotonin.
It readily crosses the blood brain barrier. Histamine plays a direct role in the body’s sleep-wake cycle, also known as the circadian rhythm.
Histamine levels should be higher during the day, and lower at night when it’s time to go to sleep.
People who have altered circadian rhythms may have higher levels of histamine at night that could contribute to sleep problems or insomnia.
As hydroxyzine impacts histamine receptors by blocking its effects, it can induce drowsiness or a calming effect on the central nervous system (CNS).
Hydroxyzine also increases levels of serotonin, which can ease anxiety and produce feelings of calm, stability, and balance.
Adequate levels of serotonin are also needed to promote a healthy sleep cycle.
While hydroxyzine is not FDA-approved for insomnia, some research does find that it can help with sleep problems relating to post-traumatic stress disorder (PTSD) and nightmares.
Hydroxyzine isn’t a cure for insomnia.
It does not correct the underlying cause of difficulty sleeping, but provides a short-term solution for relief of symptoms.
When used long-term for sleep problems, hydroxyzine will become less effective.
How Quickly Does Hydroxyzine Work?
Hydroxyzine benefits are felt quickly, usually within 15-30 minutes.
If you are taking it to help you sleep, you should take it when you are ready for bed. It reaches peak levels after 2 hours, and most effects are no longer noticeable by 4-6 hours.
Hydroxyzine can help you go to sleep, and may also help you sleep through the night.
It is used as a sedative prior to general anesthesia, but the sedation effects are dose-dependent.
How Long Does Hydroxyzine Last?
In adolescents, it may be shorter. In older adults and people with impaired kidney or liver function, it can stay in the body longer.
Higher doses may lead to more side effects, like next-day drowsiness.
Your healthcare provider will prescribe the lowest effective dose to minimize side effects.
Hydroxyzine Dosage Guide
The typical dosage varies per person and is dependent on symptoms, medical history, age, and other health factors.
For insomnia, a healthcare provider may prescribe 10-50 mg, taken once daily before bed.
Is Hydroxyzine Habit Forming?
While some sleep aids are habit-forming, hydroxyzine is not.
It is not a controlled substance and has no risk of addiction.
While taking it long-term may decrease its effectiveness for sleep, hydroxyzine is not addictive.
Hydroxyzine Side Effects
Most medications cause side effects that may range from mild to severe.
Hydroxyzine has some common side effects that are typically mild.
In some cases, severe effects could occur.
Be sure to inform your medical provider and pharmacist about your prescription medications, over-the-counter medicines, and any supplements or herbs you’re taking.
These all have the potential to interact with drugs, including hydroxyzine.
By avoiding medication interactions, you may also avoid preventable side effects or complications.
Common Side Effects
Hydroxyzine does not have a lot of common side effects.
The ones that occur most commonly include:
More Serious Side Effects
In some cases, it is possible for hydroxyzine to cause serious side effects.
Stop taking it if you notice any of the following and report them to your medical provider immediately.
If you experience seizures, tremoring, problems breathing, or any other severe reaction, get emergency medical care right away.
Serious side effects of hydroxyzine include:
- Unintentional tremoring, trembling, or shaking
- Rash or redness of the skin
- Pus-filled or blister-like sores
Hydroxyzine Drug Interactions
There are many potential drug interactions with hydroxyzine.
The following medications may have interactions:
- Other sleeping pills, sedatives, or tranquilizers
- Other antihistamines
- Certain antidepressants such as citalopram (Celexa) or fluoxetine (Prozac)
- Muscle relaxers
- Anti-anxiety medication
- Narcotic pain relievers
- Anticonvulsant medication
- Malaria medication
- Certain cancer treatments
- Medication for HIV/AIDS
- Certain heart rhythm medications such as amiodarone (Cordarone, Nexterone, others), quinidine (Nuedexta), sotalol (Sorine, Sotylize), others
- Anti-nausea medications such as ondansetron (Zofran)
- Certain antibiotics such as azithromycin (Zithromax), clarithromycin (Biaxin), erythromycin (Eryc), others
This is not a complete list of all possible interactions.
Check with your healthcare provider and pharmacist for more detailed information regarding interactions with other medications, OTC drugs, or supplements that you take.
What to Avoid
Hydroxyzine can be effective for certain conditions, but there are other times that it should be avoided.
- Older people who are over age 65 could have stronger side effects with hydroxyzine. It is not commonly prescribed in this population, as there are safer medications for insomnia in older adults.
- Hydroxyzine is not safe for people who are pregnant, trying to become pregnant, or who are breastfeeding. It can cause fetal harm or increased risk of birth defects, and may pass through to the infant through breast milk. There are safer sleep aids for pregnancy.
- Avoid taking hydroxyzine if you are allergic to any active or inactive ingredients.
- Do not take hydroxyzine if you have a prolonged QT interval. Hydroxyzine is also contraindicated for people who have a history of heart attack, heart failure, or heart disease.
- Hydroxyzine may cause severe side effects in people with low blood levels of magnesium or potassium.
- Do not take hydroxyzine with alcohol or illegal drugs, as this can increase the risk of adverse effects.
- Seek urgent medical care if you take too much hydroxyzine, since overdose is possible and can cause severe effects.
When to See a Doctor
If you struggle with occasional insomnia or trouble falling asleep, your healthcare provider may recommend hydroxyzine.
While there are many OTC and prescription medications for sleep problems, hydroxyzine can be effective for short-term use.
You should only take hydroxyzine for sleep problems or insomnia if your healthcare provider prescribes it. Personalized medical advice is important to avoid potential complications.
If you’re having a mental health emergency, call 911 or go to the nearest emergency room. You can also get free 24/7 support from a suicide and crisis expert by calling or texting 988. If you’d prefer to chat online, you can chat with a suicide and crisis expert by visiting the Lifeline Chat.
How K Health Can Help
Did you know you can access online urgent care with K Health?
Check your symptoms, explore conditions and treatments, and if needed, text with a healthcare provider in minutes.
K Health’s AI-powered app is HIPAA compliant and is based on 20 years of clinical data.
Frequently Asked Questions
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.
K Health has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.
Sleep Health and Appropriate Use of OTC Sleep Aids in Older Adults—Recommendations of a Gerontological Society of America Workgroup. (2017).
Prescription Medications for the Treatment of Insomnia and Risk of Suicide Attempt: a Comparative Safety Study. (2019).
Modifying effects of histamine on circadian rhythms and neuronal excitability. (2001).
Pharmacologic management of patient behavior. (2016).
Serotonin and sleep. (2002).
Comparing the effect of prazosin and hydroxyzine on sleep quality in patients suffering from posttraumatic stress disorder. (2014).
Bilastine vs. hydroxyzine: occupation of brain histamine H1-receptors evaluated by positron emission tomography in healthy volunteers. (2014).
Hydroxyzine hydrochloride. (2020).
Vistaril (hydroxyzine pamoate). (n.d.).