The Dangers of Mixing Alcohol and Zzzquil (Diphenhydramine HCL)

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Zzzquil is an over-the-counter sedative containing the antihistamine diphenhydramine, the same active ingredient as Benadryl. The Food and Drug Administration (FDA) warns that taking higher-than-recommended doses of diphenhydramine is dangerous (1), and using Zzzquil with alcoholic beverages should be avoided. (2) Like alcohol, Zzzquil is a central nervous system (CNS) depressant and can cause extreme drowsiness. Although it’s not uncommon for people to take sedating drugs while drinking, doing so can be hazardous and potentially result in life-threatening respiratory depression.

If you’ve been struggling to control your drinking while using Zzzquil, you might need to consider the possibility you have an alcohol use disorder. You can learn more by contacting Guardian Recovery for a free, no-obligation assessment and health benefits check. We’ll put you in touch with an addiction treatment advisor who will explain your options and gather the information needed to develop an effective long-term treatment plan tailored to your needs and goals.

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Risks of Combining Alcohol & Zzzquil

The main ingredient in ZzzQuil is either diphenhydramine hydrochloride or doxylamine succinate, depending on the formulation. Antihistamines such as these effectively reduce many allergy-related symptoms, including eye, throat, and nose irritations. Doxylamine effects tend to last longer than diphenhydramine, but it is not intended for use in children under 12. 

When combined with alcohol, the total impact of these substances on the CNS can be amplified, leading to adverse outcomes. There are several possible risks related to drinking alcohol while using Zzzquil. They range from minor to severe and may be due to a combination of individual and circumstantial factors.


Zzzquil and alcohol can cause heavy sedation and drowsiness, impairing coordination and reaction time. Combining them can intensify these side effects leading to cognitive and mobility impairments. This can be dangerous even when engaging in mundane activities, but driving a motor vehicle or operating heavy machinery can be life-threatening. You could place yourself and others at significant risk of severe or lethal injuries.

Loss of Consciousness

Some people are more predisposed to losing consciousness when sedated than others. Combining Zzzquil and alcohol is more likely to induce a loss of consciousness in these individuals. This can be detrimental due to the likelihood of falls, other accidents, and injuries.


Zzzquil and alcohol are both known to cause dehydration, so combining them can compound this effect, cause extreme thirst and discomfort, and exacerbate a hangover.

Learning & Memory Impairments

The primary ingredient in Zzzquil blocks the action of the chemical messenger acetylcholine. (4) Acetylcholine is needed for learning and memory, so blocking its activity can temporarily interfere with these processes. Alcohol is also known to inhibit functions related to learning and memory, so mixing alcohol and diphenhydramine may have a more significant effect on these two processes.

Interactions With Other Medications

Diphenhydramine can interact with cough and cold remedies, intensifying side effects. Certain medications used with Zzzquil and alcohol could also heighten the risk of adverse effects, including antidepressants, anti-anxiety drugs, and other depressants. recommends you ask your doctor before taking Zzzquil with “a sleeping pill, narcotic pain medicine, muscle relaxer, or medicine for anxiety, depression, or seizures.” (5)

Sex (Male or Female)

Because women’s bodies typically contain less water, when they consume alcohol, it tends to be more concentrated than in men–thereby making them more vulnerable to alcohol-related harm. For this reason, combining Zzzquil with alcohol may be particularly dangerous for women, as smaller amounts of alcohol are needed to trigger adverse effects.

Zzzquil Misuse or Heavy Alcohol Consumption

As noted, the FDA announced in 2020 that taking doses of diphenhydramine above recommended amounts can result in “serious heart problems, seizures, coma, or even death.” (3) Excessive use of this medication is reportedly due to its intoxicating effects, including hallucinations and delusions. Unfortunately, the amount needed to achieve these effects may have the potential to be lethal.

While Zzzquil and other OTC sleep aids are not believed to be habit-forming, the same cannot be said for alcohol. Repeated binges and prolonged heavy drinking can lead to alcohol dependence and all the risks that come with it. There can be many short- and long-term consequences of alcohol misuse, including health conditions, emotional distress, strained relationships, and legal and financial issues.

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Effects of Zzzquil on Sleep

Diphenhydramine and doxylamine are medications used to control allergies, but their sedative effects also make them effective at promoting sleep. Histamines are inflammatory chemical compounds in the body released in response to an injury or foreign substance. Antihistamines block the activity of these compounds and prevent them from carrying out their functions.

Both antihistamines found in Zzzquil products are known as “first-generation.” (6) Unlike their newer counterparts, they don’t discriminate which histamines they block. Instead, they cross the blood-brain barrier and inhibit a histamine function involving sleep regulation, which soon results in drowsiness. Effects last approximately 4-6 hours for diphenhydramine and 7-8 hours for doxylamine.

Some Zzzquil products contain other ingredients, such as the naturally-occurring hormone melatonin (7) and the pain-reliever acetaminophen. Although melatonin does not directly induce sleep, increasing levels cause you to experience a state of quiet wakefulness that helps promote slumber. Adult liquid formulations are 10% alcohol, but you would consume only a minimal amount if you take Zzzquil as directed.

The Effects of Alcohol on Sleep

Although alcohol can help you fall asleep, your sleep might not be high quality. Health experts believe alcohol harms an essential sleep cycle phase known as rapid eye movement (REM). Even if you finish drinking six hours before bed, interruptions during the first two REM cycles can cause you to feel fatigued when you awaken. (8) Also, the more alcohol you consume, the more significant the impact on your sleep may be, possibly contributing to other issues such as sleep apnea.

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If you’ve engaged in polysubstance misuse involving alcohol, Zzzquil, or other depressants, you may be at risk for severe or life-threatening complications. While you can discontinue using Zzzquil without adverse effects, abrupt alcohol cessation can lead to dangerous withdrawal symptoms. For this reason, you are urged to undergo a medically-supervised detox instead of attempting to withdraw at home. Clinical detox programs are overseen by health providers, who will monitor your withdrawal and administer medication as needed to relieve side effects.

Following detox, you may require intensive treatment to address your emotional dependence on alcohol and examine the many factors contributing to your desire to misuse substances. Enrolling in a comprehensive recovery program allows you to access integrated, customized, evidence-based treatment in a safe, controlled environment. 

If you are ready to reclaim the life you deserve, contact Guardian Recovery and learn how we can help you permanently end the cycle of addiction.


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Disclaimer: Does not guarantee specific treatment outcomes, as individual results may vary. Our services are not a substitute for professional medical advice or diagnosis; please consult a qualified healthcare provider for such matters.

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Reviewed professionally for accuracy by:

Ryan Soave


Ryan Soave brings deep experience as a Licensed Mental Health Counselor, certified trauma therapist, program developer, and research consultant for Huberman Lab at Stanford University Department of Neurobiology. Post-graduation from Wake Forest University, Ryan quickly discovered his acumen for the business world. After almost a decade of successful entrepreneurship and world traveling, he encountered a wave of personal and spiritual challenges; he felt a calling for something more. Ryan returned to school and completed his Master’s Degree in Mental Health Counseling. When he started working with those suffering from addiction and PTSD, he found his passion. He has never looked back.

Written by:

Cayla Clark

Cayla Clark

Cayla Clark grew up in Santa Barbara, CA and graduated from UCLA with a degree in playwriting. Since then she has been writing on addiction recovery and psychology full-time, and has found a home as part of the Guardian Recovery team.

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