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Unisom vs ZzzQuil – Which Is The Best OTC Sleep Aid?

Insomnia is a sleep disorder in which you may have problems staying asleep, falling asleep, or both.


In the United States, an estimated 15% of adults claim to have chronic insomnia and around 35% of adults report that they have had symptoms of insomnia within the last year, according to the National Sleep Foundation.

Insomnia is more common in seniors than younger people and is about twice as common in females than in males.

According to a recent study, an employee with insomnia loses 8 days of work performance a year.

Lost productivity related to insomnia costs the United States economy over $64 billion per year.


Short-term insomnia can be caused by an illness, life stresses (like – the death of a loved one, job change or loss, or moving), or environmental factors, like – noise, light, or extreme temperatures.

Chronic insomnia can be caused by:

Lifestyle patterns:

  • poor sleeping environment, such as – hallway lights which are always turned on, disruption of sleep to complete nursing care, noise in rooms and hallways at night, and long periods in bed;
  • rotating shift work;
  • lack of routine for sleeping and waking;
  • frequent daytime napping;
  • physical inactivity (sedentarism);
  • jet lag due to often travel across multiple time zones.

The use of certain stimulants and medications, including:

  • stimulant laxatives;
  • alcohol (it often causes awakening in the middle of the night and prevents deeper stages of sleep);
  • nicotine;
  • antidepressants;
  • illicit drugs, like – cocaine;
  • diuretics;
  • beta-blockers;
  • allergy and cold medications which contain pseudoephedrine;
  • chemotherapy drugs;
  • caffeine, a CNS stimulant usually found in cola drinks, some teas, and coffee; drinking them in the evening can keep you from falling asleep at bedtime.

Long-term medical conditions, such as:

  • Parkinson’s disease;
  • asthma;
  • Alzheimer’s disease;
  • chronic obstructive pulmonary disease;
  • bipolar disorder (a disorder which causes periods of abnormally elevated mood and periods of depression);
  • sleep apnea;
  • depression;
  • congestive heart failure;
  • anxiety;
  • diabetes;
  • emotional stress;
  • acid reflux;
  • urinary incontinence (any uncontrolled leakage of urine);
  • hyperthyroidism;
  • menopause;
  • fibromyalgia;
  • restless leg syndrome (an uncontrollable urge to move your legs);
  • nasal/sinus allergies;
  • low back pain.

Risk Factors

Risk factors which can contribute to sleep problems include:

  • being depressed;
  • being in a long-term care facility;
  • having retention of blood in your legs;
  • the regular use of SSRI or tricyclic antidepressants;
  • having Parkinson’s disease;
  • having diabetes;
  • having a disease of the spinal cord nerves;
  • having low iron levels;
  • older age;
  • the regular use of sedatives or alcohol to put yourself to sleep;
  • having heart failure, hypertension, or atrial fibrillation;
  • having heartburn;
  • having enlarged tonsils;
  • recent bereavement;
  • having a wide neck;
  • having to go to the bathroom repeatedly during the night;
  • being female.


Common symptoms of insomnia include:

  • increase in accidents and mistakes;
  • waking up too early;
  • problems with memory;
  • feeling as if you haven’t slept at all;
  • difficulty concentrating;
  • being awake for much of the night;
  • mood changes;
  • sleeping for only short periods;
  • irritability;
  • daytime sleepiness;
  • lying awake for a long time before you fall asleep;
  • trouble returning to sleep.

When to Call the Doctor

Call your doctor when:

  • you have noticed changes in your energy, mood, and appetite;
  • you wake up during the night due to physical pain;
  • you notice excessive heartburn which keeps you awake at night;
  • the symptoms of insomnia interfere with your ability to function and daytime activities;
  • the symptoms of insomnia last longer than a month;
  • when trying to sleep, you observe an uncomfortable sensation in your leg;
  • you have started to take a new medication which may have as a side effect sleep problems;
  • you are concerned about possible sleep apnea (a disorder that is marked by snoring when breathing is disrupted during sleep).


Your healthcare professional will ask you about your lifestyle, medical history, and mental health conditions.

In addition, he may ask you to take a blood test.


As part of a treatment plan, your healthcare professional might recommend the following:

  • use relaxation techniques, such a mindfulness meditation before going to bed;
  • develop a regular bedtime routine;
  • avoid watching the clock;
  • use the bedroom just for sleep and intimacy;
  • avoid prolonged use of smartphones, TV, computers, or reading devices before bed;
  • try to cut down or completely avoid alcohol, caffeine, and smoking;
  • regular physical exercise during the day;
  • reduce as much as possible the use of diuretics and appetite suppressants;
  • have a warm bath before bed;
  • keep the bedroom quiet, dark, and not too warm;
  • try lying on your back with a pillow under your knees, if you have a back disorder;
  • go to sleep at the same time every night;
  • do not go to bed thinking about work.

If the above treatment doesn’t work, your healthcare professional may prescribe medicines for your sleep problems, such as:

  • antipsychotics;
  • benzodiazepines (a class of drugs primarily used for treating anxiety);
  • barbiturates;
  • quinazolinones;
  • selective gamma-aminobutyric acid medication;
  • nonbenzodiazepines hypnotics.

Here Is A Comparison Between Two Over-The-Counter Sleep Medicines:


It contains doxylamine, a first-generation antihistamine, which reduces the effects of the neurotransmitter histamine in the human body.


It contains diphenhydramine, a first generation H1-antihistamine, that is part of a family of medications known as antihistamines.

Inactive ingredients:

  • sodium citrate;
  • alcohol;
  • sodium benzoate;
  • citric acid anhydrous;
  • saccharin sodium;
  • FD&C Blue No. 1;
  • purified water;
  • FD&C Red No. 40;
  • propylene glycol;
  • flavor;
  • polyoxyl 40 stearate;
  • high fructose corn syrup.


Both are used to treat:

  • itching;
  • skin rash;
  • hives;
  • watery eyes;
  • a runny nose;
  • sneezing.

In addition, these antihistamines are used for the temporary relief of sleeplessness at night.

Side Effects

The most common adverse events associated with Unisom include:

  • blurred vision;
  • hallucinations;
  • constipation;
  • confusion;
  • drowsiness;
  • dizziness;
  • dry nose, mouth, or throat;
  • little or no urinating.

The most common adverse events associated with ZzzQuil include:

  • a feeling like you might pass out;
  • fluttering in your chest;
  • loss of coordination;
  • pounding heartbeats;
  • dry mouth, nose, or throat;
  • painful urination;
  • day-time drowsiness;
  • little or no urinating;
  • blurred vision;
  • confusion;
  • upset stomach;
  • uncontrollable movements of your tongue;
  • constipation;
  • drowsiness;
  • dizziness;
  • tightness in your neck.


The usual dosage of Unisom for adults and children 12 years of age and older is 25 to 50 milligrams taken by mouth at bedtime.

The usual dosage of ZzzQuil for adults and children 12 years of age and older is 30 mL at bedtime.

Warnings & Precautions

Do not take any of these antihistamines if you:

  • have taken an MAO inhibitor within the past 2 weeks;
  • are allergic to ingredients of the medication;
  • have narrow-angle glaucoma;
  • have an enlarged prostate;
  • have stenosing peptic ulcer (a break in the inner lining of the stomach);
  • have chronic lung disease;
  • have asthma;
  • have an obstructed bladder.

Drug Interactions

These antihistamines may interact in a negative way with the following drugs:

  • carvedilol;
  • atropine;
  • dronedarone;
  • azelastine;
  • disopyramide;
  • belladonna;
  • glycopyrrolate;
  • botulinum toxins;
  • methamphetamine;
  • brimonidine;
  • mifepristone;
  • captopril;
  • galantamine;
  • degarelix;
  • lopinavir;
  • dextromethorphan;
  • clarithromycin;
  • dofetilide;
  • mirtazapine;
  • doxorubicin;
  • nabilone;
  • dronabinol;
  • olopatadine;
  • flecainide;
  • potassium chloride;
  • ketotifen;
  • ciprofloxacin;
  • baclofen;
  • clobazam;
  • codeine;
  • granisetron;
  • cetirizine;
  • tamoxifen;
  • pimozide;
  • tiotropium;
  • quinidine;
  • tramadol;
  • quinine;
  • zopiclone;
  • ropinirole;
  • tranylcypromine;
  • rufinamide;
  • tolterodine.


Drinking alcohol while taking any of these antihistamines can make all of their side effects worse.

Is It Safe During Pregnancy or Breastfeeding?

Both antihistamines may harm a nursing baby as they may pass into breast milk. Both are not expected to be harmful to a developing fetus.

However, it is best to not use these antihistamines without your doctor’s advice.

Conclusion – Unisom vs ZzzQuil

The active ingredient in Unisom is doxylamine, whereas the active ingredient in ZzzQuil is diphenhydramine HCl. Both are first-generation antihistamines which can help to induce sleep. However, some studies have concluded that doxylamine is the strongest sedative antihistamine.