Cetirizine

What Does Cetirizine Do?

Cetirizine is an antihistamine, primarily used for treating allergy symptoms like hay fever, hives, and other allergic skin conditions. It counteracts the effects of histamine, a substance in the body that causes allergic responses. Additionally, it's used in the treatment of chronic urticaria and sometimes, off-label, for pruritus associated with certain skin conditions. It's known for its ability to dampen allergic reactions without causing excessive drowsiness.

How Does Cetirizine Work?

Cetirizine works by obstructing the action of histamine in the body. It binds to the H1 receptor, blocking histamine from attaching and initiating the allergic reaction. Subsequently, this minimises allergic indicators like sneezing, itching and a runny nose. In addition, Cetirizine possesses anti-inflammatory properties, curtailing the release of pro-inflammatory cytokines and chemokines, thereby improving its effectiveness in treating chronic urticaria.

Drug Type and Category of Cetirizine

Drug Type:

Cetirizine is classified as a H1 receptor antagonist, which means it works by blocking the histamine receptors in the body that are responsible for many of the allergic symptoms. 

Second-Generation Antihistamine:

As a second-generation antihistamine, cetirizine is designed to be more selective in targeting peripheral histamine receptors (outside the brain) compared to first-generation antihistamines. This selectivity leads to a reduced sedative effect, which is a common side effect of older, first-generation antihistamines like diphenhydramine (Benadryl). Second-generation antihistamines, such as cetirizine, are less likely to cross the blood-brain barrier and, therefore, have a lower likelihood of causing drowsiness or impairing cognitive function, making them preferable for daytime use.

What dosage of Cetirizine should you be taking?

NHS Recommendations ¹

The National Health Service (NHS) provides dosage guidelines for Cetirizine based on the age group and condition being treated. Below are the general dosage recommendations:

For Hay Fever (Allergic Rhinitis) and Urticaria (Hives):

Adults and Children over 12 years:

• Recommended dose: 10 mg once daily (1 tablet).
• Maximum dose: 10 mg per day.
• Cetirizine should be taken orally, with or without food.

Children 6 to 12 years:

• Recommended dose: 5 mg once daily (half a 10 mg tablet).
• In some cases, the dose can be increased to 10 mg per day if necessary, under medical supervision.
• Cetirizine is available in liquid form for younger children to make dosing easier.

Children 2 to 5 years:

• Recommended dose: 2.5 mg once daily (half of the 5 mg tablet or the appropriate dose of liquid formulation).
• If needed, the dose can be increased to 5 mg once daily (under a doctor's guidance).

Children under 2 years:

Cetirizine is not recommended for children under 2 years of age without a doctor’s advice.

For Kidney Problems (Renal Impairment):

• Adults with severe renal impairment (creatinine clearance < 10>
• For those with moderate renal impairment, dosing adjustments should be made based on the doctor's recommendation

For Elderly Patients:

In elderly patients with normal kidney function, the standard dose (10 mg daily) is typically safe. However, for those with reduced kidney function, the dose may need to be adjusted.

What are the side-effects of Cetirizine?

Cetirizine, like all medications, can cause side effects, although not everyone will experience them. Most side effects of cetirizine are very mild (if at all), but in rare cases, more serious reactions may occur.

Common Side Effects:

These are usually mild and may go away as your body adjusts to the medication:

1. Drowsiness or tiredness: Although cetirizine is a second-generation antihistamine and less likely to cause drowsiness compared to first-generation antihistamines, some people may still experience mild sedative effects.
2. Headache: A mild headache can occur in some people.
3. Dry mouth: Cetirizine can cause dryness in the mouth, which may be uncomfortable.
4. Gastrointestinal issues: This can include stomach pain, nausea, or diarrhea.
5. Dizziness: A feeling of lightheadedness or dizziness may occur in some individuals.

Less Common Side Effects:

These are less likely but could occur in some individuals:

1. Rash or itching: This may be an allergic reaction to the medication.
2. Fatigue: Some individuals may feel unusually tired or weak.
3. Sore throat or cough: These may occur but are not as common.
4. Difficulty sleeping (insomnia): Some people may experience trouble sleeping, although this is rare.

Serious Side Effects (Rare):

These require immediate medical attention:

1. Severe allergic reactions: Symptoms can include difficulty breathing, swelling of the face or throat (angioedema), and skin reactions such as hives.
2. Severe dizziness or fainting: This could indicate a more serious side effect and needs medical evaluation.
3. Fast or irregular heartbeat: A rapid or unusual heart rate may indicate a serious issue, and medical attention should be sought.
4. Liver problems: Signs can include yellowing of the skin or eyes (jaundice), dark urine, or persistent abdominal pain.

Interactions

Cetirizine can interact with several medications, potentially increasing the risk of side effects or reducing the effectiveness of the drugs involved. 

One of the most significant interactions is with alcohol and central nervous system (CNS) depressants, such as sedatives, tranquilizers, and pain medications. These substances can enhance the sedative effects of cetirizine, leading to excessive drowsiness, dizziness, and impaired cognitive or motor function. Therefore, it is advisable to limit alcohol consumption or avoid it while taking cetirizine. 

Another key interaction is with theophylline, a medication used in asthma treatment, which can increase the plasma concentration of cetirizine, raising the risk of side effects like drowsiness and dizziness. Cetirizine should also not be combined with other antihistamines, as this can lead to increased sedation and dryness of the mouth. 

Additionally, ritonavir, an HIV medication, can raise the blood levels of cetirizine, potentially increasing the risk of adverse effects. Caution is also advised when combining cetirizine with other sedative medications, such as benzodiazepines or opioids, as this can result in excessive sedation. 

Medications that affect liver enzymes, such as some antifungal drugs like ketoconazole, may alter the metabolism of cetirizine, leading to higher drug concentrations in the body. Similarly, certain antidepressants or antipsychotics, particularly tricyclic antidepressants like amitriptyline, can enhance the sedative effects of cetirizine. 

Natural Alternatives to Cetirizine

Quercetin ²

Quercetin is a plant flavonoid with anti-inflammatory and antioxidant properties. It acts as a natural antihistamine by inhibiting the release of histamine from mast cells, which are involved in allergic reactions. Quercetin has been studied for its potential to relieve allergy symptoms such as sneezing, runny nose, and itching. It can be found in foods like apples, onions, and broccoli.

Stinging Nettle (Urtica dioica) ³

Stinging nettle is a popular herbal remedy that has shown anti-inflammatory and anti-histamine effects. It is often used to treat allergic rhinitis.Stinging nettle can help reduce symptoms such as runny nose, sneezing, and itching due to its natural antihistamine and anti-inflammatory properties. They can be cooked, blended into a smoothie, or boiled in hot water to make tea. Some people on social media have tested stinging nettles directly on the skin by stinging themselves daily, and generally report good improvements in reduction in hayfever. DYOR (do your own research) though. 

Bromelain ⁴

Bromelain is an enzyme found in pineapples. It has anti-inflammatory properties and may help to reduce nasal congestion and other symptoms of allergies. Research suggests that bromelain can help reduce inflammation and mucus production in the respiratory tract, which can be helpful for treating allergy symptoms.

Probiotics ⁵

Probiotics are beneficial bacteria that can help regulate the immune system. They can be found in yogurt, kefir, and other fermented foods. Probiotics can help modulate the immune system and reduce inflammation, potentially alleviating allergy symptoms. Research has shown that certain strains of probiotics can improve symptoms of allergic rhinitis.

Vitamin C ⁶

Vitamin C is an antioxidant that has natural antihistamine properties. It can help reduce the production of histamine in the body. Taking vitamin C supplements may help reduce symptoms such as runny nose, itchy eyes, and nasal congestion.

Interesting facts about Cetirizine

In many countries, cetirizine is classified as Category B for pregnancy, meaning animal studies have not shown any risk to the fetus, though there is limited human data. However, it is always recommended to consult a healthcare provider before using cetirizine during pregnancy.

Cetirizine is widely available over-the-counter (OTC) in many countries, making it easily accessible for people with seasonal allergies or other allergic conditions without the need for a prescription.

Some studies ⁷ suggest that cetirizine may improve sleep quality in individuals suffering from allergy symptoms at night, as it helps reduce nasal congestion and other symptoms that can disrupt sleep.

Disclaimer

This article is generated for informational purposes only. It was created in December 2024. Medications and medical guidance can change over time. Therefore, it is essential to consult with your general practitioner or healthcare provider before making any decisions regarding medications or treatment plans. Your GP can provide personalised advice based on your specific health needs and conditions.

References

1. https://www.nhs.uk/medicines/cetirizine/
2. Khaki, A., Sahebkar, A., & Hekmatdoost, A. (2020). The potential of quercetin in allergic disorders: A review of current evidence. Nutrients, 12(8), 2410.
3. Bafunno, V., Pippione, M., & De Luca, C. (2018). Natural remedies for allergic rhinitis: A review. American Journal of Clinical Nutrition, 108(2), 299–312.
4. Blumenthal, M., Goldberg, A., Brin, Y., & Perkal, Z. (2016). Bromelain: A comprehensive review of therapeutic applications. Journal of Medicinal Food, 19(5), 403–409.
5. Lai, K. P., Shek, L. P., Heng, P. H., Wong, H. K., & Hooi, L. S. (2015). Probiotics and the management of allergic diseases: A meta-analysis. Clinical and Experimental Allergy, 45(3), 691–704.
6. Alipour, E., Asadollahi, K., & Asadi, Z. (2017). The effect of vitamin C supplementation on allergic rhinitis: A systematic review and meta-analysis. International Archives of Allergy and Immunology, 172(2), 93–100.
7. Tinkelman, D. G., & Bousquet, J. (2002). Clinical and pharmacological profile of cetirizine in the treatment of allergic rhinitis. The Journal of Allergy and Clinical Immunology, 109(2), 336-343. doi:10.1067/mai.2002.119768.