Zzzquil is an antihistamine with anticholinergic and sedative effects. It competes with histamine for H1-receptor sites on effector cells in the GI tract, blood vessels and respiratory tract.
Zzzquil has anti-histaminic (H1-receptor), anti-emetic, anti-vertigo and sedative and hypnotic properties . The anti-histamine action occurs by blocking the spasmogenic and congestive effects of histamine by competing with histamine for H1 receptor sites on effector cells, preventing but not reversing responses mediated by histamine alone . Such receptor sites may be found in the gut, uterus, large blood vessels, bronchial muscles, and elsewhere . Anti-emetic action is by inhibition at the medullary chemoreceptor trigger zone . Anti-vertigo action is by a central antimuscarinic effect on the vestibular apparatus and the integrative vomiting center and medullary chemoreceptor trigger zone of the midbrain .
Zzzquil is used for the treatment of followings:
- Seasonal, perennial, vasomotor rhinitis
- Urticaria, angioneurotic oedema, anaphylaxis
- Pruiritic conditions
- Premedication for emesis and motion sickness
- Miscellaneous like meniere's disease and parkinsonism
Zzzquil is also used to associated treatment for these conditions: Allergic Rhinitis (AR), Allergic cough, Allergies, Anaphylaxis, Angioedema, Common Cold, Common Cold/Flu, Conjunctival irritation, Cough, Cough Variant Asthma, Cough caused by Common Cold, Eye allergy, Fever, Insect Bites, Insect Stings, Insomnia, Irritative cough, Itching of the nose, Itching of the throat, Motion Sickness, Nasal Congestion, Oral Mucositis, Pain, Parkinsonian Syndromes, Pollen Allergy, Productive cough, Pruritus, Rash, Rhinorrhoea, Sinus Congestion, Sinus headache, Skin Irritation, Sneezing, Sunburn, Symptoms of Acute Bronchitis Accompanied by Coughing, Upper respiratory tract hypersensitivity reaction, site unspecified, Urticaria, Dermatographism, Dry cough, Watery itchy eyes, Airway secretion clearance therapy, Expectorant
How Zzzquil works
Zzzquil predominantly works via the antagonism of H1 (Histamine 1) receptors . Such H1 receptors are located on respiratory smooth muscles, vascular endothelial cells, the gastrointestinal tract (GIT), cardiac tissue, immune cells, the uterus, and the central nervous system (CNS) neurons . When the H1 receptor is stimulated in these tissues it produces a variety of actions including increased vascular permeability, promotion of vasodilation causing flushing, decreased atrioventricular (AV) node conduction time, stimulation of sensory nerves of airways producing coughing, smooth muscle contraction of bronchi and the GIT, and eosinophilic chemotaxis that promotes the allergic immune response .
Ultimately, diphenhydramine functions as an inverse agonist at H1 receptors, and subsequently reverses effects of histamine on capillaries, reducing allergic reaction symptoms . Moreover, since diphenhydramine is a first-generation antihistamine, it readily crosses the blood-brain barrier and inversely agonizes the H1 CNS receptors, resulting in drowsiness, and suppressing the medullary cough center .
Furthermore, H1 receptors are similar to muscarinic receptors . Consequently, diphenhydramine also acts as an antimuscarinic . It does so by behaving as a competitive antagonist of muscarinic acetylcholine receptors, resulting in its use as an antiparkinson medication .
Lastly, diphenhydramine has also demonstrated activity as an intracellular sodium channel blocker, resulting in possible local anesthetic properties .
|Availability||Rx and/or OTC|
|Diphenhydramine Other Names||Difenhidramina, Diphenhydramine, Diphenhydraminum|
|Related Drugs||Gocovri, prednisone, ibuprofen, acetaminophen, hydroxyzine, amitriptyline, lorazepam, ondansetron, cetirizine, loratadine|
|Weight||Average: 255.3547 |
|Protein binding|| |
Some prescribing information records the protein binding of diphenhydramine as approximately 78% while others have suggested the medication is about 80 to 85% bound to plasma proteins.
|Therapeutic Class||Sedating Anti-histamine|
|Available Country||Canada, United States,|
|Last Updated:||June 7, 2022 at 8:54 pm|
Table Of contents
- Side Effect
- Uses during Pregnancy
- Uses during Breastfeeding
- Accute Overdose
- Food Interaction
- Half Life
- Volume of Distribution
- Interaction With other Medicine
- Most allergic conditions: 25-50 mg three times a day with a further 50 mg at night.
- 1 to 5 years of age: 5 mg i.e., 2.5 ml of elixir 4 times a day
- More than 6 years of age: 10 mg i.e. 5 ml of elixir 4 times a day
Side effect includes sedation, dizziness, tinnitus, fatigue, ataxia, blurred vision, diplopia, euphoria, and epigastric discomfort.
Overdose is expected to result in effects similar to the adverse effects that are ordinarily associated with the use of diphenhydramine, including drowsiness, hyperpyrexia, and anticholinergic effects, among others . Additional symptoms during overdose may include mydriasis, fever, flushing, agitation, tremor, dystonic reactions, hallucinations and ECG changes . Large overdose may cause rhabdomyolysis, convulsions, delirium, toxic psychosis, arrhythmias, coma and cardiovascular collapse . Moreover, with higher doses, and particularly in children, symptoms of CNS excitation including hallucinations and convulsions may appear; with massive doses, coma or cardiovascular collapse may follow .
Although diphenhydramine has been in widespread use for many years without ill consequence, it is known to cross the placenta and has been detected in breast milk . This medication should therefore only be used when the potential benefit of treatment to the mother exceeds any possible hazards to the developing fetus or suckling infant .
Pharmacokinetic studies indicate no major differences in the distribution or elimination of diphenhydramine compared to younger adults . Nevertheless, diphenhydramine should be used with caution in the elderly, who are more likely to experience adverse effects . Avoid use in elderly patients with confusion .
The results of a review on the use of diphenhydramine in renal failure suggest that in moderate to severe renal failure, the dose interval should be extended by a period dependent on Glomerular filtration rate (GFR) .
After intravenous administration of 0.8 mg/kg diphenhydramine, a prolonged half-life was noted in patients with chronic liver disease which correlated with the severity of the disease . However, the mean plasma clearance and apparent volume of distribution were not significantly affected .
LD50=500 mg/kg (orally in rats). Considerable overdosage can lead to myocardial infarction (heart attack), serious ventricular dysrhythmias, coma and death.
Caution should be exercised with patients in whom drowsiness is undesirable e.g., drivers, machine operators. Concomitant consumption of alcohol or central nervous system (CNS) depressants will potentiate drowsiness.
Zzzquil administration significantly reduces the absorption of the antituberculous agent para-aminosalicyclic acid (PAS) from the gastrointestinal tract. CNS depressants may potentiate the sedative action of Zzzquil. Anticholinergic drugs may potentiate Zzzquil’s anticholinergic side effects.
- Avoid alcohol.
- Take before a meal. Take 30 minutes before a meal or 30 minutes before departure for motion sickness.
Zzzquil Alcohol interaction
[Moderate] GENERALLY AVOID:
Use of anticholinergic agents with alcohol may result in sufficient impairment of attention so as to render driving and operating machinery more hazardous.
In addition, the potential for abuse may be increased with the combination.
The mechanism of interaction is not established but may involve additive depressant effects on the central nervous system.
No effect of oral propantheline or atropine on blood alcohol levels was observed in healthy volunteers when administered before ingestion of a standard ethanol load.
However, one study found impairment of attention in subjects given atropine 0.5 mg or glycopyrrolate 1 mg in combination with alcohol.
Alcohol should generally be avoided during therapy with anticholinergic agents.
Patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them.
Zzzquil Drug Interaction
Moderate: duloxetine, duloxetine, pregabalin, pregabalin, alprazolam, alprazolam, cetirizine, cetirizine
Unknown: aspirin, aspirin, omega-3 polyunsaturated fatty acids, omega-3 polyunsaturated fatty acids, acetaminophen, acetaminophen, cyanocobalamin, cyanocobalamin, ascorbic acid, ascorbic acid, cholecalciferol, cholecalciferol
Zzzquil Disease Interaction
Moderate: anticholinergic effects, asthma/COPD, cardiovascular, renal/liver disease, glaucoma, liver disease, resp depression
Volume of Distribution
Zzzquil is widely distributed throughout the body, including the CNS . Following a 50 mg oral dose of diphenhydramine, the volume of distribution is in the range of 3.3 - 6.8 l/kg .
Zzzquil is quickly absorbed after oral administration with maximum activity occurring in approximately one hour . The oral bioavailability of diphenhydramine has been documented in the range of 40% to 60%, and peak plasma concentration occurs about 2 to 3 hours after administration .
The elimination half-life ranges from 2.4-9.3 hours in healthy adults . The terminal elimination half-life is prolonged in liver cirrhosis .
Values for plasma clearance of a 50 mg oral dose of diphenhydramine has been documented as lying in the range of 600-1300 ml/min .
The metabolites of diphenhydramine are conjugated with glycine and glutamine and excreted in urine . Only about 1% of a single dose is excreted unchanged in urine . The medication is ultimately eliminated by the kidneys slowly, mainly as inactive metabolites .
Pregnancy & Breastfeeding use
Category B: There are no adequate and well controlled studies in pregnant women using diphenhydramine hydrochloride. Therefore, diphenhydramine hydrochloride should be used in pregnancy only if clearly needed. Zzzquil hydrochloride has been reported to be excreted in breast milk and thus, use of diphenhydramine hydrochloride in lactating mother is not recommended.
Known hypersensitivity to Zzzquil Hydrochloride, Ammonium chloride is contra-indicated in presence of impaired hepatic or renal function.
Symptoms: Impaired consciousness; psychosis, seizures, antimuscarinic symptoms (e.g. mydriasis, tachycardia, tachyarrhythmias), resp failure, rhabdomyolysis; acute delirium with visual and auditory hallucination (topical).
Management: Supportive and symptomatic treatment. Convulsions and marked CNS stimulation may be treated with IV diazepam.
Store between 15-30° C. Protect from moisture.
Zzzquil contains Diphenhydramine see full prescribing information from innovator Zzzquil Monograph, Zzzquil MSDS, Zzzquil FDA label
What is Zzzquil used for?
Zzzquil is an antihistamine used to relieve symptoms of allergy, hay fever, and the common cold. These symptoms include rash, itching, watery eyes, itchy eyes/nose/throat, cough, runny nose, and sneezing. It is also used to prevent and treat nausea, vomiting and dizziness caused by motion sickness.
How safe is Zzzquil?
The U.S. Food and Drug Administration is warning that taking higher than recommended doses of the common over-the-counter (OTC) allergy medicine diphenhydramine can lead to serious heart problems, seizures, coma, or even death.
How does Zzzquil work?
Zzzquil works by blocking the action of histamine, a substance in the body that causes allergic symptoms.
What are the common side effects of Zzzquil?
Common side effects of Zzzquil are include:
- dry mouth, nose, and throat
- loss of appetite
- increased chest congestion
- muscle weakness
- excitement (especially in children)
Is Zzzquil safe during pregnancy?
Zzzquil is considered to be safe during pregnancy. Doctors and nurses recommend this OTC medication to help relieve allergy symptoms, even while you're pregnant. Recent studies have found Zzzquil to be safe.
Is Zzzquil safe during breastfeeding?
Small, occasional doses of Zzzquil would not be expected to cause any adverse effects in breastfed infants.
Can I drink alcohol with Zzzquil?
Alcohol may increase drowsiness and dizziness while you are taking Zzzquil. You should be warned not to exceed recommended dosages and to avoid activities requiring mental alertness. If your doctor prescribes these medications together, you may need a dose adjustment to safely take this combination.
Can I drive after taking Zzzquil?
Do not drive or operate machinery if Zzzquil makes you drowsy or affects your judgment.
When should be taken of Zzzquil?
When Zzzquil is used to treat motion sickness, it is usually taken 30 minutes before departure and, if needed, before meals and at bedtime.
How often can I take Zzzquil?
Zzzquil is usually taken every 4 to 6 hours.
How much Zzzquil can I take in a day?
For adults and teens, the Zzzquil dosage is 25 to 50 mg every 4 to 6 hours. The maximum amount you should take in one day is 300 mg. Keep in mind, taking higher doses can increase the risk of side effects, including drowsiness.
Is Zzzquil bad for my liver?
Despite widespread use over many decades, Zzzquil has not been linked to liver test abnormalities or to clinically apparent liver injury. The reason for its safety may relate its short half-life and limited duration of use.
How long does Zzzquil take to work?
It normally takes about 30 minutes to work. Common side effects include feeling sleepy, dizzy or unsteady on your feet. You may also have difficulty concentrating and have a dry mouth.
Can I take Zzzquil on an empty stomach?
Zzzquil may be taken with or without food. Take exactly as directed. Do not take more than is recommended.
How long does Zzzquil stay in my system?
A half-life of a drug determines how long it will take for 50% of it to flush out of your system. Depending on the median value that the individual lands on, Zzzquil can stay in your system anywhere between 13.2 and 49 hours.
Can Zzzquil be taken long-term?
Caution should be exercised for long-term use of Zzzquil, an antihistamine and a non-benzodiazepine sedative-hypnotic, because of the association of increased risk for dementia.
How long can I use Zzzquil?
Do not use Zzzquil for longer than 2 weeks to treat sleep problems, or longer than 7 days to treat cold or allergy symptoms.
Who should not take Zzzquil?
If you have increased pressure in the eye, closed angle glaucoma, high blood pressure, stenosing peptic ulcer you should not take Zzzquil.
What happen If I suddenly stop taking Zzzquil?
Although withdrawal symptoms of Zzzquil are minor compared to harder drugs, you may experience cold sweats, nausea, or diarrhea when stopping the drug suddenly.
What happen If I missed Zzzquil?
Since Zzzquil is used when needed, you may not be on a dosing schedule. If you are on a schedule, use the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not use extra medicine to make up the missed dose.
What happen if I take too much Zzzquil?
Taking more than the normal Zzzquil dosage can be harmful. Serious side effects from too much of the Zzzquil can include nausea, vomiting, blurred vision, trouble breathing, hallucinations, unconsciousness, and seizures.
Can Zzzquil cause heart problems?
Taking too much Zzzquil can lead to serious heart problems, seizures, coma, or death.
Can Zzzquil cause heart palpitations?
A fast heartbeat is a common side effect of Zzzquil. In rare cases, it can become serious.
Can Zzzquil damage kidneys?
In general, Zzzquil do not cause kidney problems.