Zyrtec, also known as cetirizine, is a popular over-the-counter antihistamine medication used to treat allergy symptoms such as sneezing, watery eyes, and runny nose. The standard adult dose of Zyrtec is 10 mg once daily. Some people wonder if taking a higher dose, such as 20 mg per day, is safe and effective. Here is a look at the evidence regarding taking 20 mg of Zyrtec daily.
What is Zyrtec?
Zyrtec contains the active ingredient cetirizine hydrochloride, which is a second-generation antihistamine. It works by blocking histamine receptors in the body that cause allergy symptoms when histamine binds to them. By preventing histamine from attaching to receptors, Zyrtec stops the immune system’s allergy response.
Zyrtec is specifically classified as a selective H1 receptor antagonist, meaning it selectively targets the H1 histamine receptors responsible for allergic reactions. This makes it less likely to cause unwanted side effects compared to older, first-generation antihistamines like diphenhydramine (Benadryl) that can cross the blood-brain barrier and cause sedation.
Zyrtec starts working within 1 hour and provides 24 hours of relief from common allergy symptoms. It’s available over-the-counter in 10 mg tablets, chewable tablets, and syrup for both adults and children over 6 months old.
Zyrtec Dosage Guidelines
The recommended dosage of Zyrtec for adults and children over 6 years old is 10 mg once daily. This 10 mg tablet can be taken with or without food and does not need to be taken at the same time each day, although taking it consistently at the same time may help with adherence.
For children under 6 years old, the recommended dose of Zyrtec based on age is:
- 6 months to 2 years: 1.25 mg twice daily
- 2 to 5 years: 2.5 mg once daily
- 6 to 11 years: 5 mg once daily
Zyrtec syrup is available for children, providing 1 mg of cetirizine per 1 mL. Caregivers can use an oral syringe to measure out the proper dose.
These standard Zyrtec dosages are considered safe and effective for controlling allergy symptoms in most people. Exceeding the recommended dose is generally not recommended or studied.
Is it Safe to Take 20 mg of Zyrtec Daily?
The safety of taking 20 mg of Zyrtec per day depends on who is taking it. There is some research looking at higher doses for adults, but no studies have evaluated the safety of giving children 20 mg of Zyrtec daily.
Adults
Some research in adults suggests that taking up to 20 mg of Zyrtec per day appears relatively safe for many people. However, side effects may be more likely at higher doses.
One study had adults take 10 mg or 20 mg of Zyrtec daily for 4 weeks. People taking 20 mg daily had a greater reduction in allergy symptoms and higher blood levels of the drug compared to those taking 10 mg per day. Drowsiness was the most common side effect, reported by 36% of people taking 20 mg versus 19% of those taking 10 mg.
Another study had adults with chronic idiopathic urticaria (hives) take up to 40 mg of Zyrtec per day for 6 weeks. The 20 mg and 40 mg daily doses were significantly more effective at reducing hives compared to the standard 10 mg dose. Sedation was once again the most common side effect, reported by 48% of those in the 40 mg group, 36% in the 20 mg group, and 21% in the 10 mg group.
So while minimal research has found 20 mg of Zyrtec daily to be effective in adults, the higher dose is associated with an increase in potentially problematic drowsiness compared to the standard 10 mg dose.
Children
There are no studies evaluating the safety or efficacy of giving children 20 mg of Zyrtec daily. The effects of excessive antihistamine doses in children can include serious side effects like irregular heartbeat, seizures, hallucinations, and coma.
Therefore, without medical supervision, it is not recommended to give 20 mg of Zyrtec to a child. Sticking to the standard age-appropriate dosing guidelines is the safest approach.
Side Effects of Zyrtec
At the recommended dosage of 10 mg per day, Zyrtec is generally well tolerated in most people. Potential side effects are usually mild and may include:
- Drowsiness
- Fatigue
- Dry mouth
- Sore throat
These effects often improve with continued use as the body adjusts to the medication. However, at higher doses like 20 mg per day, sedation is more likely to occur and can interfere with daily activities in some people.
Rare but serious side effects possible with Zyrtec include difficulty breathing, swelling of the face/tongue/lips, hives, rash, and fast or irregular heartbeat. Seek prompt medical care if any of these reactions occur.
Interactions With Zyrtec
Several drugs and supplements can interact with Zyrtec and increase the risk of side effects. These include other antihistamines, antidiarrheals, antifungals, antibiotics like erythromycin, and the supplement St. John’s wort.
Drinking alcohol while taking Zyrtec can also enhance sedation. It’s best to avoid alcohol when taking Zyrtec, especially at higher doses like 20 mg daily where drowsiness is more likely.
Before taking any new medications, vitamins, or supplements, check with a pharmacist or doctor about potential interactions with Zyrtec.
Is 20 mg of Zyrtec More Effective Than 10 mg?
For some people, 20 mg of Zyrtec per day may provide better allergy relief than the standard 10 mg dose. However, the increased efficacy comes with a greater risk of side effects like sedation.
In studies of adults with chronic idiopathic urticaria or hives, 20 mg of Zyrtec daily significantly reduced hive symptoms better than 10 mg per day. But drowsiness was 75% more common in the 20 mg group compared to the 10 mg group.
Similarly, research in adults with seasonal allergies found that 20 mg of Zyrtec daily further decreased allergy symptoms like runny nose, sneezing, and itchy eyes compared to 10 mg. Yet again, sedation was almost twice as common in those taking 20 mg versus 10 mg.
So while 20 mg per day may provide some additional antihistamine benefits for allergies and hives, the higher dose also comes with a greater risk of problematic drowsiness in many people. This can interfere with daily activities like driving, work, school, and exercise.
Other Ways to Enhance the Effects of Zyrtec
Rather than simply increasing the Zyrtec dose and risking additional side effects, there are other ways to get enhanced allergy relief from taking 10 mg per day:
- Take it consistently – Make sure to take Zyrtec every day as prescribed instead of sporadically when symptoms worsen. Consistent use allows blood levels to remain optimal.
- Use it with a nasal spray – Pair Zyrtec with an OTC nasal corticosteroid spray like Flonase. This provides additional relief for congestion and nasal symptoms.
- Avoid triggers – Identify and limit exposure to things that trigger your allergies like pet dander, pollen, dust mites.
- Use allergy covers – Use dust mite covers on pillows/mattresses and HEPA air filters to reduce allergens.
- See an allergist – Ask about prescription antihistamines or immunotherapies if OTC medication remains inadequate.
Should I Take 20 mg of Zyrtec?
For adults struggling to control allergy or hive symptoms with standard doses of Zyrtec, taking up to 20 mg daily might provide better relief. However, higher doses also increase the risk of side effects like sedation. Make sure any increase is monitored closely by your healthcare provider.
There is no established safety or effectiveness of giving children doses of Zyrtec higher than the recommended amount based on age. Stick to the standard children’s dosing unless advised differently by your pediatrician.
To enhance the effects of Zyrtec, focus on taking it as directed, using allergen avoidance measures, adding a nasal spray, and seeing a specialist for other treatment options. With an individualized approach, most people can find adequate allergy relief from Zyrtec at the standard OTC dosage without needing to take more.
Zyrtec Dosage FAQs
What is the normal dosage of Zyrtec?
The standard Zyrtec dosage for adults and children over 6 years old is 10 mg once daily. For younger children, the dose is adjusted based on age down to 1.25 mg twice daily for those 6 months to 2 years old.
Is it okay to take 20 mg of Zyrtec a day?
Some research suggests 20 mg of Zyrtec daily could be tolerated in adults, but may increase the risk of side effects like sedation. There are no studies establishing the safety of giving children 20 mg per day.
Can I take 40 mg of Zyrtec per day?
Doses above 20 mg daily have not been sufficiently studied for safety or effectiveness. A dose of 40 mg per day increases the risks of side effects without clear additional benefits.
What happens if I accidentally take 2 Zyrtec pills in one day?
Accidentally taking two 10 mg Zyrtec tablets for a total of 20 mg in one day is unlikely to cause serious harm in healthy adults. However, side effects like pronounced drowsiness are more likely. If concerning reactions occur, seek medical advice.
Can Zyrtec be taken twice a day?
Zyrtec is formulated to provide 24-hour relief with just once daily dosing. Taking it more than once per day increases the risk of side effects without added benefit and is not recommended.
The Bottom Line
Zyrtec is a helpful OTC antihistamine for controlling allergy symptoms when taken at the recommended dosage of 10 mg once daily for adults and children over 6 years old. While some research suggests taking up to 20 mg per day could be effective in adults, the higher dose also increases the risk of side effects like sedation.
There is no established safety or efficacy of giving children more than the standard dose of Zyrtec based on their age. Focus on proper use, trigger avoidance, add-on therapies, and specialist care rather than exceeding the recommended Zyrtec dosage, especially in kids.
