ZzzQuil vs NyQuil

ZzzQuil vs NyQuil – detailed comparison:


It is the brand name of an OTC medication that is used as a sleep remedy. Its main active ingredient is diphenhydramine HCl, a first generation H1-antihistamine.

This medication works by blocking a certain natural substance – histamine (a neurotransmitter which is involved in the proper digestion, immune system, and the central nervous system) which the human body makes during an allergic reaction.


It is used for the relief of occasional sleeplessness, particularly if you have difficulty falling asleep.

In addition, this medication is used alone or with other medications to treat shaking and muscle stiffness caused by Parkinson’s disease (a degenerative disorder of the central nervous system) as well as to treat and prevent nausea, vomiting, and dizziness caused by motion sickness.


For sleep problems, the usual recommended dosage is 50mg at bedtime.

Note – it is not intended to use for children under 12 years old.

Side Effects And Precautions

Common side effects may include:

  • hyperactivity;
  • dizziness;
  • dry nose or mouth;
  • confusion;
  • light sensitivity;
  • upset stomach;
  • irregular heart rate;
  • clumsiness;
  • difficulty urinating;
  • headaches;
  • thick lung secretions;
  • drowsiness;
  • low blood pressure;
  • increased pressure within the eye;
  • blurry vision;
  • constipation;
  • erectile dysfunction;
  • sweating.

Less common side effects may include:

  • delirium;
  • agitation;
  • feeling unsteady;
  • sleepiness;
  • seizures;
  • severe drowsiness;
  • hallucinations;
  • tremors;
  • nervousness;
  • coma.

Before using this antihistamine, tell your healthcare provider if you have:

  • bladder neck obstruction;
  • allergy to any medicine;
  • GI obstruction;
  • cardiovascular disease;
  • asthma (a chronic disease that causes the airways to become inflamed);
  • hyperthyroidism;
  • glaucoma (a serious condition that damages the optic nerve, which is crucial to good vision);
  • prostate problems;
  • chronic obstructive pulmonary disease.

Drug Interactions

It may negatively interact with other medications, especially:

  • methadone;
  • codeine;
  • potassium iodide;
  • dihydrocodeine;
  • procarbazine;
  • rasagiline;
  • selegiline;
  • ethanol;
  • selegiline transdermal;
  • hydrocodone;
  • melatonin;
  • thalidomide;
  • isocarboxazid;
  • tranylcypromine;
  • phenelzine;
  • trimethobenzamide;
  • pramlintide;
  • tramadol;
  • promethazine;
  • tamsulosin;
  • sodium oxybate.

Pregnancy & Breastfeeding

This medication is not considered safe during pregnancy, particularly during the first trimester.

In addition, it may pass into breast milk and negatively affect the infant. Tell your doctor that you are breastfeeding a baby before using this medication.


It is not recommended that you mix alcohol with this medication since both depress the activity of the central nervous system. Additionally, it can result in life-threatening effects, like – slowed respiration, and even coma.


It is a combination of doxylamine, dextromethorphan, and acetaminophen, which are used to treat a cough, sneezing, fever, headaches, sore throat, and runny nose in children 12 years and older and adults. Sometimes, it is used for insomnia.

Doxylamine is an antihistamine drug that reduces the effects of the natural chemical histamine in the body. This neurotransmitter can produce symptoms of watery eyes, itching, sneezing, and runny nose.

Dextromethorphan is a cough suppressant that affects the cough reflex in the brain, which triggers coughing. Acetaminophen is a fever reducer and pain reliever.


It is used to treat a cough, headaches, runny nose, body aches, fever, itching, sneezing, and watery eyes caused by the common cold, allergies, or the flu.

In addition, many people have turned to this medication as a sleep aid. The sleepiness effect after taking a dose typically lasts approximately 4 to 8 hours.

Note – if you experience some sleeping difficulties, it is ok to take this medication for a few days at a time or just on an occasional basis. But, this medication is not designed to be taken for sleep on a daily basis.


The usual recommended dosage is 30 mL every 6 hours.

Note – it takes around 10 minutes to kick in the system.

Side Effects And Precautions

Common side effects may include:

  • upset stomach;
  • dry eyes;
  • mild dizziness;
  • dry mouth or nose;
  • drowsiness;
  • constipation;
  • mild skin rash;
  • sleep problems (insomnia);
  • headaches;
  • blurred vision;
  • feeling excited or restless (particularly in children);
  • trouble concentrating.

Rare side effects may include:

  • severe drowsiness;
  • pounding heartbeat;
  • restless muscle movements;
  • little or no urinating;
  • feeling light-headed;
  • slow or shallow breathing;
  • tremor;
  • seizure (convulsions);
  • dark urine;
  • unusual bleeding;
  • hallucinations;
  • uneven heartbeats;
  • clay-colored stools;
  • severe headaches;
  • loss of appetite;
  • confusion;
  • pale skin;
  • yellowing of the skin or eyes;
  • pain in the upper stomach;
  • easy bruising.

READ MORE: Alka Seltzer vs Tums

Pregnancy & Breastfeeding

The medication is excreted in small quantities in breast milk and may negatively affect the breastfed baby. Tell your doctor that you are breastfeeding a baby before using this medication.

Also, avoid this medication if you are pregnant since prenatal exposure to acetaminophen is associated with an increased risk of behavioral problems in children, especially when taken during the 3rd trimester of pregnancy, according to a 2016 study that was issued in the journal JAMA Pediatrics.


To be sure that this antihistamine is safe for you, tell your healthcare professional if you have other medical conditions, especially:

  • overactive thyroid;
  • liver disease;
  • if you take monoamine oxidase inhibitors;
  • glaucoma;
  • blockage in your digestive tract;
  • if you take potassium supplements;
  • pheochromocytoma (tumor of the adrenal gland);
  • a history of alcoholism;
  • coronary artery disease;
  • heart disease;
  • bladder obstruction.

READ MORE: Lovaza vs Vascepa

Drug Interactions

It may negatively interact with other medications, especially:

  • blood thinners, such as – warfarin;
  • non-steroidal anti-inflammatory drugs, such as – ibuprofen (Advil, Motrin), naproxen (Aleve), or diclofenac;
  • diuretics;
  • medicines used to prevent blood clots, such as – dalteparin, tinzaparin, enoxaparin, or fondaparinux.


Avoid drinking alcoholic beverages while taking this antihistamine since alcohol may increase your risk of liver damage and can increase the risk of other severe side effects.

READ MORE: Zicam vs Airborne

Bottom Line – ZzzQuil vs NyQuil

ZzzQuil (active ingredient – diphenhydramine) is a medication that is used as a sleep remedy and sneezing, runny nose, watery eyes, itching, and other cold or allergy symptoms.

NyQuil (active ingredients – doxylamine, dextromethorphan, and acetaminophen) is a medicine that is used to treat a headache, fever, runny nose, sneezing, and sore throat caused by allergies, the common cold, or the flu as well as sleep problems.

In conclusion, both medicines are useful for treating allergy symptoms and short-term sleep problems, but they both have plenty of side effects.

For instance, NyQuil contains alcohol that will cause liver damage if it becomes a habit. On the other hand, ZzzQuil has the active ingredient diphenhydramine, which can strip your heart valves if it becomes a habit.

There are also potentially severe side effects that are rare when using these medications, such as – low blood cell counts, anaphylaxis, seizures, and toxic psychosis.

READ THIS NEXT: Theraflu vs Dayquil



Leave a Comment