Unisom vs ZzzQuil

Unisom vs ZzzQuil – detailed comparison:


It is the brand name of a drug called doxylamine, a first-generation antihistamine.

This antihistamine works by reducing the effects of histamine, a neurotransmitter in the body, which produces symptoms such as a runny nose, itching, and watery eyes.


This medication is typically used as a short-term treatment for insomnia (sleep problems). Insomnia is a condition described by difficulty staying asleep or falling asleep and is considered chronic if it occurs at least three nights per week for at least 90 days.

Approximately 60 million people in the US are affected by sleep problems every year. The causes of insomnia can vary, but they typically include:

  • illness;
  • emotional stress;
  • pain or discomfort at night;
  • excessive worry;
  • physical discomfort;
  • jet lag;
  • poor sleep hygiene practices;
  • receiving bad news;
  • intake of stimulants, such as – nicotine, caffeine, and alcohol;
  • using certain medicines, including some which are used to treat nasal/sinus allergies, depression, colds, hypertension, and asthma;
  • anxiety;
  • depression;
  • life circumstances;
  • spending too much time with the blue-tinted screens, such as – tablets or smartphones;
  • shift-work;
  • environmental factors, such as – noise, light, or temperature.

In addition, this antihistamine is used to treat a runny nose, watery eyes, sneezing, skin rash, hives, itching, and other allergy or cold symptoms.


For insomnia, the usual recommended dose is 25mg per day, taken 30 minutes before bedtime.

Notes – the medication can increase the risk of falls, hence, seniors shouldn’t use it. It can be used in adults and children 12 years of age and older.

If you have trouble sleeping, you should not use this antihistamine for more than 14 days unless recommended by your healthcare professional.

Side Effects and Precautions

Common side effects may include:

  • drowsiness;
  • mild dizziness;
  • stomach pain;
  • blurred vision;
  • loss of coordination;
  • headaches;
  • constipation;
  • dry nose, mouth, or throat;
  • sweating;
  • thick lung secretions.

Less common side effects may include:

  • sensitivity to light;
  • irregular heart rate;
  • erectile dysfunction;
  • hyperactivity;
  • seizures;
  • low blood pressure;
  • severe drowsiness or dizziness;
  • hallucinations;
  • toxic psychosis;
  • difficulty urinating;
  • low blood cell counts;
  • constipation;
  • abnormal heart rhythms;
  • blurred or double vision;
  • severe allergic reaction;
  • confusion;
  • acute labyrinthitis (inner ear problems);
  • little or no urinating.


Consuming alcoholic beverages while using this antihistamine is not recommended since alcohol can increase the risk of side effects.

Drug Interactions

It may negatively interact with other medications, especially:

  • Cymbalta (duloxetine);
  • Adderall (amphetamine/dextroamphetamine);
  • gabapentin;
  • Benadryl (diphenhydramine);
  • lisinopril;
  • cyclobenzaprine;
  • omeprazole;
  • omega-3 polyunsaturated fatty acids;
  • Tylenol (acetaminophen);
  • ibuprofen;
  • airborne;
  • Zyrtec (cetirizine);
  • levothyroxine;
  • Xanax (alprazolam);
  • melatonin;
  • trazodone;
  • tramadol.

Pregnancy & Breastfeeding

This medication may pass into breast milk and negatively affect a nursing baby. Do not use this antihistamine without a healthcare provider’s advice if you are breastfeeding an infant.

Moreover, this medication is not expected to be harmful to a developing fetus. Do not use this antihistamine without a healthcare provider’s advice if you are pregnant or plan to fall pregnant.


It is a popular sleep supplement that is based on the original product called Nyquil. It was designed for people who are healthy but are simply having trouble sleeping.

The main active ingredient in this medicine is diphenhydramine, an antihistamine that works by binding to the H1 histamine receptor and functions as an inverse agonist.


This sleep supplement is used to induce sleep, to treat motion sickness and certain symptoms of Parkinson’s disease.

In addition, it is used to treat sneezing, hives, skin rash, watery eyes, runny nose, itching, and other cold or allergy symptoms.


As a sleep aid, take this supplement within half an hour before bedtime. Do not use it for children under 12 years of age.


Ask your healthcare professional if it is safe for you to take this medicine if you have other medical conditions, particularly:

  • if you take a potassium supplement;
  • glaucoma;
  • a colostomy or ileostomy;
  • a thyroid disorder;
  • asthma;
  • blockage of the digestive tract;
  • a cough with mucus;
  • bladder obstruction;
  • liver disease;
  • low blood pressure;
  • chronic obstructive pulmonary disease;
  • heart disease;
  • kidney disease;
  • a cough caused by smoking, emphysema, or chronic bronchitis.

READ MORE: Dayquil vs Nyquil – Differences

Side Effects and Precautions

Common side effects may include:

  • constipation;
  • day-time drowsiness after night-time use;
  • dry nose, mouth, or throat;
  • loss of coordination;
  • upset stomach;
  • blurred vision;
  • dizziness;
  • dry eyes;
  • drowsiness.

Less common side effects may include:

  • confusion;
  • uncontrollable movements of the tongue;
  • little or no urinating;
  • fluttering in the chest;
  • difficult urination;
  • tightness in the neck or jaw;
  • a feeling like you might pass out;
  • pounding heartbeats.

READ MORE: Theraflu vs Alka Seltzer

Drug Interactions

It may negatively interact with other medications, especially:

  • Aleve (naproxen);
  • Benadryl (diphenhydramine);
  • Control (phenylpropanolamine);
  • Adderall (amphetamine/dextroamphetamine);
  • cyclobenzaprine;
  • gabapentin (a medication that is used to treat partial seizures);
  • phentermine;
  • Advil (ibuprofen);
  • Lexapro (escitalopram);
  • Klonopin (clonazepam);
  • Tylenol PM (acetaminophen/diphenhydramine);
  • lisinopril;
  • omeprazole;
  • amoxicillin;
  • oxycodone (sold under brand names such as OxyContin and Percocet);
  • metoprolol;
  • tramadol;
  • Prozac (fluoxetine);
  • trazodone;
  • ibuprofen (a medication that is used for treating fever, pain, and inflammation);
  • Xanax (alprazolam);
  • Tylenol (acetaminophen);
  • Zoloft (sertraline);
  • Zyrtec (cetirizine);
  • melatonin.


Drinking alcoholic beverages while taking this sleep supplement can notably increase the risk of side effects.

Pregnancy & Breastfeeding

Avoid using this sleep supplement if you are breastfeeding a baby since this medication passes into breast milk and can negatively affect the infant, plus, it may decrease milk production.

Additionally, avoid using this sleep supplement during pregnancy, especially during the third trimester, since it may result in premature birth.

READ MORE: Alka Seltzer vs Tums

Bottom Line – Unisom vs ZzzQuil

Unisom (active ingredient – doxylamine) is an antihistamine that can cause drowsiness and is occasionally used a sleep aid.

It is typically used to treat hives, skin rash, itching, sneezing, runny nose, watery eyes, and other cold or allergy symptoms. It works by reducing the effects of histamine in the body.

ZzzQuil (active ingredient – diphenhydramine) is an OTC medication that is used to induce sleep, to treat motion sickness and allergy symptoms. The primary active ingredient in this medication is also the primary ingredient in almost every other OTC sleep medication and even nighttime pain reliever.

The problem with these medicines is that they don’t fix the real cause of sleep disorders.

Additionally, they both have a half-life of around 9 hours. This will leave some people to experience morning drowsiness, which increases the risk of falls and driving incidents, especially for seniors.

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