ZzzQuil: Uses, Dosage, Side Effects, And Is It Addictive?

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Medical News TodaySubscribeWhat to know about ZzzQuil

Medically reviewed by Alan Carter, Pharm.D. — Written by Jessica Caporuscio, PharmD on May 17, 2019

Uses
How to take
Side effects
Precautions
Who should avoid
Is ZzzQuil addictive?
Summary

ZzzQuil is an over-the-counter nighttime sleep aid. The active ingredient in ZzzQuil is diphenhydramine, which is also the active ingredient in the allergy medication Benadryl.

Diphenhydramine is an antihistamine that people commonly use to treat allergic reactions, itchiness, and hives. The most common side effect of diphenhydramine is drowsiness.

ZzzQuil is a safe and effective medication for treating short-term sleeping difficulties, or insomnia, in people over 12 years old. However, individuals with certain medical conditions, such asthma and heart disease, should speak to a doctor before taking ZzzQuil.

Read on for more information on the uses, dosage, and safety of taking ZzzQuil. We also discuss whether ZzzQuil can be addictive.

Uses

man taking zzzquil at night wondering about side effects — A person should use ZzzQuil as a short-term aid for occasional problems with sleep.

The active ingredient in ZzzQuil is an antihistamine called diphenhydramine.

Antihistamines reduce the effect of histamines, which are natural chemicals that the body produces during an allergic reaction.

Diphenhydramine binds to the histamine-1 receptor in the body. This receptor is present in many areas of the body, including the respiratory tract, abdominal tract, immune cells, and brain.

Antihistamines such as diphenhydramine are common ingredients in allergy and cold medications.

The most significant side effect of diphenhydramine is drowsiness, which is due to the effect that some antihistamines can have on the brain.

The manufacturer recommends using ZzzQuil for relieving occasional sleeplessness. ZzzQuil works by helping to reduce the time it takes for a person to fall asleep.

How to take ZzzQuil

Adolescents and adults can use ZzzQuil as a short-term aid for occasional problems getting to sleep. The manufacturer states that children under the age of 12 years should not use this medication.

The recommended dose of ZzzQuil is 50 mg at bedtime when needed, or as a person’s doctor directs. ZzzQuil is available in both liquid and capsule forms.

For the liquid form, a single 50 milligram dose is equal to 30 milliliters, or 2 tablespoons. Liquid ZzzQuil comes with a special cup for measuring out the correct dose.

For the capsule form, a single 50 mg dose is equal to two ZzzQuil capsules. A person cannot cut, chew, or split the capsules.

People should not take more than 50 mg of ZzzQuil in a single day.

The liquid form of ZzzQuil contains 10% alcohol. ZzzQuil is also available in an alcohol-free liquid solution, which may be more appropriate for adolescents.

Side effects

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Side effects of diphenhydramine can include headaches and drowsiness.

Diphenhydramine, which is the active ingredient in ZzzQuil, can cause side effects in some people.

The most common side effects of diphenhydramine include:

drowsiness
dizziness
loss of coordination
headaches
upper abdominal pain
thickened mucus in the lungs
dry mouth and nasal passages
stimulation of the central nervous system
constipation
euphoria
involuntary muscle movements
painful or difficult urination
low blood pressure
blurred or double vision
irregular heartbeat
sensitivity to light
erectile dysfunction
early periods
anorexia

Rarely, more serious side effects can occur, including:

severe allergic reactions
abnormal heart rhythm
anemia

Precautions

The intended use of ZzzQuil is for occasional sleeplessness. The manufacturer recommends that people consult a doctor if they experience sleeping difficulties continuously for more than 2 weeks, as this may be a symptom of a more serious medical condition.

Because ZzzQuil causes drowsiness, it may affect a person’s ability to drive or operate heavy machinery. It is also important to avoid drinking alcohol when taking ZzzQuil as this can increase drowsiness.

Older adults should use ZzzQuil with caution as side effects such as drowsiness, dizziness, and low blood pressure can increase the risk of falling.

Taking ZzzQuil may worsen certain medical conditions, including:

asthma
hyperthyroidism
heart disease
high blood pressure
glaucoma

Individuals with these conditions should consult their doctor before taking ZzzQuil.

People who experience urinary difficulties while taking ZzzQuil should stop taking the medication and speak to a doctor.

Who should avoid ZzzQuil?

Not everyone can take ZzzQuil. People should not give ZzzQuil to children under the age of 12 years.

The active ingredient of ZzzQuil can pass into breastmilk, so people who are breastfeeding should consult a doctor before taking it. Pregnant women should also seek medical advice before using this medication.

People taking monoamine oxidase inhibitors (MAOIs), which are a type of antidepressant, should avoid taking ZzzQuil or speak to a doctor first. MAOIs can worsen some of the side effects of antihistamines.

Although ZzzQuil contains diphenhydramine, which can help relieve allergy symptoms, it can still cause allergic reactions in some people. Anyone who has previously had an allergic reaction to ZzzQuil or medicines containing diphenhydramine should avoid taking it.

Is ZzzQuil addictive?

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A person may have worsened sleeplessness due to withdrawal symptoms from a diphenhydramine dependancy.

According to a 2010 review, diphenhydramine is among the list of medications misused by people presenting to the emergency department for drug treatment.

Antihistamines are widely available OTC medications. The drowsing effect of antihistamines can help relieve sleeplessness and anxiety.

Taking too much diphenhydramine can cause a calming effect and mild euphoria. Some people misuse diphenhydramine for its hallucinogenic effects, which may occur at doses of 300–700 mg.

Diphenhydramine is not additive at the recommended dosage. However, taking very large doses of diphenhydramine, such as over 1,000 mg per day, for a prolonged period can lead to dependence.

People who become dependent on diphenhydramine can experience withdrawal symptoms when they stop taking it. These may include:

worsened sleeplessness
runny nose
stomach upset
irritability
restlessness
abdominal cramps
sweating
diarrhea

Doctors usually recommend a gradual dosage reduction schedule for people who become dependent on diphenhydramine. This detox program help treat the person’s dependence and minimizes uncomfortable withdrawal symptoms.

Case reports of adolescents and adults with diphenhydramine dependence highlight how important it is for doctors to ask about OTC medication use, particularly in people with previous or current addictions and psychotic illnesses.

Summary

ZzzQuil is a safe and effective medication that can help relieve occasional sleeplessness. However, people should stop using ZzzQuil and see a doctor if sleeping difficulties persist for more than 14 consecutive days.

ZzzQuil is not suitable for everyone. Children under 12 years old should not take ZzzQuil, and women who are pregnant or breastfeeding should speak to a doctor first.

ZzzQuil can also interact with some antidepressants and can worsen certain medical conditions, such as asthma and heart disease. Side effects of ZzzQuil may increase the risk of falls in older people.

ZzzQuil is not addictive at the recommend dosage. However, people who take very high doses of ZzzQuil for a prolonged period may be at risk of becoming dependent.

Pediatrics / Children's Health
Pharmacy / Pharmacist
Sleep / Sleep Disorders / Insomnia
Cat 1
sleepsupplements

How we reviewed this article:

SourcesMedical News Today has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Farzam, K., & O'Rourke, M. C. (2019). Antihistamines.https://www.ncbi.nlm.nih.gov/books/NBK538188/
Gracious, B., et al. (2010). The importance of taking a history of over-the-counter medication use: A brief review and case illustration of "PRN" antihistamine dependence in a hospitalized adolescent.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3025184/pdf/cap.2010.0031.pdf
Sicari, V., & Zabbo, C.P. (2018). Diphenhydramine.https://www.ncbi.nlm.nih.gov/books/NBK526010/
Thomas, A., et al. (2009). Diphenhydramine abuse and detoxification: A brief review and case report [Abstract].https://www.ncbi.nlm.nih.gov/pubmed/18308811
ZzzQuil nighttime sleep-aid- diphenhydramine hydrochloride capsule, gelatin coated. [Fact sheet]. (2018).https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ad4babdb-d98d-420e-b8b0-9a5368c89a44
ZzzQuil nighttime sleep-aid- diphenhydramine hydrochloride liquid. [Fact sheet]. (2017).https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e441c952-cd48-4159-ada2-271ca7541600

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Medically reviewed by Alan Carter, Pharm.D. — Written by Jessica Caporuscio, PharmD on May 17, 2019

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