Cetirizine hydrochloride also known as Zyrtec is the over-the-counter medicine used as self-treatment medicine to overcome the symptoms of allergies like rhinitis and urticaria. It is a second generation antihistamine which reduces the histamine in the body. Cetirizine is a generic medicine and its brand name is zyrtec.
What is Histamine?
Histamine is a natural chemical found in the cells of the body. When someone comes in contact with particular allergens like dust or food, so in the bid to protect the body from the allergens the immune system of the body starts reacting and commands the cells to release histamine into the bloodstream. Histamine then moves to the nose, eyes, lungs, throat and skin, hence, causes symptoms of allergies like sneezing and runny nose or body rashes also known as rhinitis.
Some foods like alcohol and fermented food are high in histamine. It is also present in spoilt food. When fish get spoiled if not kept at a safe temperature it results in histamine poisoning. Symptoms of histamine poisoning are red rashes, oral burning sensation, itching, nausea, vomiting, hypotension, etc. On the bites of an insect or its sting the skin gets rashes and inflammation. These symptoms are called urticaria.
What is antihistamine?
To get relief from the symptoms of allergies we mostly pop up cetirizine pills which contain antihistamine. It works on allergies like coughing, sneezing, conjunctivitis, hay fever and allergies from insect bites or stings. Antihistamines are widely used to prevent motion sickness and vomiting. It also works for the people who experience difficulties in having good sleep. Other than cetirizine there are some common antihistamines like benadryl, zyrtec, claritin, and others. They help reduce the effect of symptoms caused by allergies.
Being a histamine H1-receptor antagonist, cetirizine, unlike first-generation antihistamines such as diphenhydramine and doxylamine, cetirizine does not cross the blood-brain barrier. Consequently, cetirizine produces minimum sedation compared to first-generation antihistamines.
Brand names of cetirizine
Allacan, Benadryl Allergy, Piriteze Allergy, Zirtek Allergy
Composition of cetirizine
Chemically cetirizine contains L (levo) and D (dexo)-stereoisomers. Levo has high chemical attraction whereas the dexo is inactive. Cetirizine is a member of the diphenylmethylpiperazine group of antihistamines.
Cetirizine, histamine receptor1 (H1) antagonist, reverses many of the effects of histamine. It reduces vascular permeability, decreases fluid escaping to tissues from capillaries. Cetirizine is also an inhibitor of histamine-induced bronchospasm.
According to the research, cetirizine may reduce the migration of neutrophils and eosinophils.
The synthetic method of cetirizine
This method comprises 4-chlorobenzhydrylchloride, hydroxyethyl piperazine (raw materials), reacts at 40-60 degree Celsius in an organic solvent which contain potassium carbonate or trimethylamine (an acid-binding agent) under the action of sodium iodide (a catalyst) and obtain intermediate 4-chloro-biphenyl-mepiquat ethanol. The molar ratio of the 4-chloro-biphenyl-mepiquat ethanol to the hydroxyethyl piperazine is 1:1 and 1:2.
The plasma protein binding of cetirizine is 93 percent.
Eco-friendly and pocket-friendly method
It is an environment-friendly method as it does not require use of chlorohydrin which is a highly toxic product. The method is very cost-effective as it needs simple instruments and apparatuses. Use of low-rate raw material, mild reaction conditions, also make it economical. Short and easy steps of the synthesis method make it suitable for large-scale production.
Dosage
A 10 mg dose of cetirizine blocks the action of histamine within 20 to 60 minutes. Its effect can last up to 24 hours. It comes in various forms like tablets, capsules and liquid also.
12 years to Adults | 10 mg | twice/day |
6 to 11 years | 5 mg | twice/day |
2 to 6 years | 2.5mg | twice/day |
Who should avoid the use of cetirizine?
Lactating mothers: A small dose is considered safe for the breast-feeding mothers. But regular use of larger doses may affect the production of milk. It may also cause drowsiness which could be harmful to the infants. The use of cetirizine in the form of ophthalmic formulation may have slight risk to the infant. To lessen the side effects, the healthcare usually advises the mothers to apply pressure over the tear duct to remove the excess solution.
Hepatic patients: Children and adults suffering with hepatic impairment are suggested to have low doses of the medicine. Approximately, 5 mg once daily is advised to such patients.
Renal impaired: People with renal dysfunction are advised to consume low doses of cetirizine. The experts suggest a dose of 5 mg/day.
Eye drops: Ophthalmologists should advise people wearing contact lenses to remove lenses before using eye drops because a bottle of 0.24 percent cetirizine hydrochloride contains benzalkonium chloride which can be absorbed by contact lenses.
People who are alcoholic should avoid the use of cetirizine. If you are under some medications like tranquilliser or sleeping pills always consult your healthcare prior to use to cetirizine.
How to take cetirizine?
The cetirizine pill can be administered with or without food. Do not chew the tablet. Just swallow the whole tablet with water or milk.
For children, cetirizine is available in liquid form also. It comes with a plastic syringe or spoon for the accurate measurement of the dose.
You can take the dose of cetirizine when you notice any symptoms of allergy. Or you can have it as a prevention from the symptoms of allergies like hay fever during spring and summer seasons.
One should have, at least, 10 to 12 hours between two doses. In case you missed the first dose, take it with a time gap of 6 hours. Do not double the dose.
Some people pop up the cetirizine pill even before travelling to prevent motion sickness.
Bioavailability of cetirizine
Cetirizine is an oral administered medicine. It gets absorbed quickly when taken in the form of tablets or syrup. The bioavailability of cetirizine is, at least, 70 percent and of levocetirizine is, at least, 85 percent. Though food does not affect the bioavailability of cetirizine, it may delay the absorption of the drug by 1 hour to 2 hours. When cetirizine is taken with fatty food the cmax (absorption time) gets delayed by 1 hour and 25 minutes.
Elimination through body
Approximately, 70 to 80 percent of cetririzine get eliminated through urine and 10 to 15 percent in faeces. In the urine, it is eliminated via an active transport mechanism. It takes 6 to 10 hours to eliminate while in elderly and hepatic patients the duration is 12 hours and 14 hours, respectively. It takes 20 hours for the elimination half-life of cetirizine among renal impairment.
Cetirizine undergoes minimal metabolic transformation and eliminates unchanged in the urine.
Safety concerns
Usually, cetirizine is a safe medicine to combat the symptoms of allergy. But do not take it in excess or you might have adverse effects.
Some of the common side effects:
Drowsiness
Nausea
Sore throat
Dry mouth
Headache
Diarrhoea
Blocked nose
Dizziness
Tips to overcome the side effects of cetirizine
Drowsiness: If you feel drowsiness after having the dose of cetirizine, you should try another antihistamine.
Nausea: Having nausea after the dose of cetirizine, take the pill with food and avoid spicy food.
Sore throat: People at the age of 16 and above should gargle with an aspirin solution (1 aspirin tablet dissolved in half a glass of water) or a mouthwash to reduce the side effects of the cetirizine pill. Children under 16 must not be administered aspirin.
Dry mouth: You can chew some gums or have sweets.
Headache: Do not consume alcohol if you are under the medication of cetirizine and drink lots and lots of water. If the problem persists, visit the doctor.
Diarrhoea: Keep yourself well hydrated in case of diarrhoea after having cetirizine and do not take any other medicine to treat the diarrhoea.
Blocked nose: In case of blocked nose or extreme runny nose or sneezing, you can replace the pill of cetirizine with another antihistamine.
Dizziness: If you feel dizzy after a dose of cetirizine, do not drive or ride a cycle or avoid going outside. Avoid any type of workout or the use of tools or machines. Take some rest unless the effects of dizziness come down.
Works on dermatologic conditions
Apart from treating the symptoms of urticaria, cetirizine is also effective in reducing the irritation of atopic eczema. Dermatologists advise higher doses of cetirizine which could be up to 40 mg (10 mg tab 4 times in a day) to get immediate and best relief from the irritation on the skin.
This histamine is combined with other antibacterial or antifungal remedies to get the best results when other medicines have non or very less effects on some patients.
It's time to call emergency
When someone has a swelled tongue, lips, throat and mouth
When someone becomes wheezy and struggles to breathe. Or feels like gasping for air
Struggling to swallow food or water
Someone turns blue. Lips and skin turn blue or pale.
Someone suddenly becomes very confused
Someone faints
A child unable to move normally and feel limp while walking. If their head is not stable or gaze is not focused
Inflammation, peeling if skin or blisters
Cetirizine does not gel with following medicines:
Cetirizine should never be administered with alcohol or other CNS (central nervous system) sedatives, such as benzodiazepines or opioids. It may lead to sedation.
Medicine taken to cure narcolepsy like pitolisant which is a histamine-3 receptor competitive antagonist and inverse agonist. The combination of pitolisant and cetirizine may affect the efficacy of the narcolepsy medicine.
Cetirizine decreases absorption of gabapentin concentrations. Gabapentin is a CNS sedative which leads to more complications.
Combination of cetirizine which is a substrate of P-glycoprotein, and verapamil which is an inhibitor of P-glycoprotein may lessen the efficiency of cetirizine and may increase the antihistamine activities.
Erdafitinib as erdatifinib is also an inhibitor of P-glycoprotein (ABCB1, MDR1), hence, should not be administered with cetirizine.
Cetirizine D or Zyrtec D is a combination drug of cetirizine and pseudoephedrine. Here D stands for decongestion. Pseudoephedrine can make you sleepy or tired. one should avoid the use of Cetirizine D if you are diabetic, or have high blood pressure, heart disease, glaucoma or suffering with thyroid disease.
Patients administered with cetirizine are sometimes put under observation by healthcare to monitor the adverse effects of it. Some adults may experience fatigue and somnolence whereas children may have headaches.
The risk of toxicity is relatively higher in the people having renal complications as the kidney excretes cetirizine. Such people should limit the usage of cetirizine.
Hepatic impaired also put under observation as the prolonged usage of cetirizine may cause damage to the liver.
FaQs
Q. How much time does it take to get relief after having cetirizine?
A. It takes around 30 minutes to 1 one to get relief from the symptoms after having cetirizine.
Q. Is the consumption of cetirizine safe if taken for a long time?
A. Cetirizine is considered a safe medicine for the relief of symptoms of allergy.
Q. Can I drive with the dose of cetirizine?
A. One should avoid driving or riding a bike or cycle because one may feel drowsy after having cetirizine.
Q. Can I have alcohol with cetirizine?
A. Avoid alcohol at all with the use of cetirizine.
Q. What should I do to combat dehydration after having cetirizine?
A. Drink plenty of water or other fluid. You can have a liquid diet to overcome dehydration.
Q. Can I take cetirizine for cough and cold?
A. Cetirizine helps prevent the symptoms of allergies like runny nose, sneezing and cough. It dries up the nasal secretion. It also helps in coughs caused due to respiratory allergies.
Q. Can I take cetirizine with other medicines?
A. Some medicines have side effects and having them with cetirizine may aggravate the problem. Always consult with your healthcare before taking cetirizine with other medicines.
Q. What is the molecular formula for cetirizine?
A. The molecular formula of cetirizine is C21H27Cl3N2O3
Q. What is the molecular weight of cetirizine?
A. The molecular weight of cetirizine is 461.8 g/mol
Q. Is cetirizine easily available?
A. It is an over-the-counter drug. Your healthcare may also prescribe it to combat some symptoms of allergy.