Loratadine vs Cetirizine: Say "No" to Allergies!

There is a range of medical drugs you can use while having seasonal allergic symptoms like itchy eyes, allergic skin rash, runny nose, and sneezing. Cetirizine and Loratadine are among the renowned medicines for treating these seasonal allergic symptoms. They work through blocking one type of Histamine receptor (H1 receptor), which prevents activation of cells with histamine making the allergic symptoms to capsize gradually. This is because histamine is the chemical compound responsible for allergic conditions. Although these two drugs are non-sedating antihistamines that employ the same mechanism to treat various allergic reactions, Cetirizine and Loratadine are quite distinct from each other.


Popularly identified under the brand names Zyrtec, Zyrtec Hives relief, and Zyrtec Allergy, Cetirizine is hydroxyzine's carboxylic acid; with its carboxylic group bearing a negative charge at physiologic pH. Hydrogen, nitrogen, chlorine, and oxygen are other elements making up its chemical composition hence its chemical formula C21H25ClN2O3. It was first discovered in 1980 in Belgium by Union Chimique Belge UCB (a multinational biopharmaceutical institution that discovered the drug Piracetam-used in the treatment of memory loss-in 1970). In spite its dawn in 1980; the Zyrtec popularity took the market by storm in 1990 after patients reported its effective results. Cetirizine is available over the counter and in its generic form.


Marketed under the brand name Claritin among other, Loratadine is a tricyclic and second-generation H1 receptor antagonist with Desloratadine as its active metabolite. The molecular formula for Loratadine is C22H23CIN2O2. The drug ranks among the safest and the most effective medicines in World Health Organization list of essential medicines. Although it was formally discovered in 1981, it became legal for use in 1993. Just like Cetirizine, it is available over the counter and in its generic form. However, in some countries, it is sold as a prescription-only drug depending on the medical condition and intended use.

Dosage and use of Loratadine and Cetirizine drugs

Both drugs are taken orally in the form of capsules. Cetirizine tablets are prescribed from as little as 5mg to a maximum of 10mg, but a 20mg tablet, which is relatively stronger, can be taken upon a prescription. In the case of Loratadine, the pills are available as of 10mg for persons aged 6 and above. Ideally, Cetirizine and Loratadine tablets are administered as a daily dosage, but one can reduce the dose as per their symptoms.

Whereas both adults and children can take Cetirizine, Loratadine is age restricted as children below the age of six cannot take the drug unless recommended by a doctor. Children aged 2 to 6 years approved to take medicines have a typical prescription of daily 5mg tablets. Lactating mothers can freely take the Cetirizine drug. However, this is not the case with Loratadine, where the mother is asked to decide on whether to breastfeed the child or not during the treatment because Loratadine concentration in breastmilk is similar to the blood levels. Nevertheless, both drugs have not been associated with any serious effects on the infants.

The central purpose of Cetirizine and Loratadine is to treat seasonal allergic symptoms. Recent studies show that Cetirizine has an added ability of treating of Rhinovirus infection and Kimura's diseases due to its anti-inflammatory agent and properties like Levocetirizine.

Interaction with other medications

Different drugs react differently when taken with Cetirizine and Loratadine. Consider the case of the drugs Erythromycin, Ketoconazole (Nizoral), and Cimetidine (Tagamet). When administered with Loratadine, they increase the levels Loratadine in the blood, by inhibiting Loratadine elimination. The results of these interactions adversely impact the health of the patient. In relation to Carbamazepine tablets like Equerto Epitol and Teril along with Rifampin and St. John's worts, these drugs reduce the blood levels of Loratadine which may also affect its intended proper functioning.

The case is the same when Cetirizine is taken with specific Theophylline tablets, such as Respbid, Theo-24, Theo-Dur, and Uniphyl. These drugs, while absorbed with Cetirizine, may increase Cetirizine's levels, as well as lessen the drugs blood pressure by 16%. Drugs prune to drowsiness should also not be taken along with Cetirizine as they will worsen the drowsiness effect of the drug. Alcohol increases the side effects of antihistamines hence should be avoided at all costs while under Cetirizine and Loratadine therapy.

Even though the aforementioned are some of the drugs that interact negatively with Cetirizine and Loratadine, it is worth noting that this list is not conclusive. Therefore, always ask your doctor if certain medications you are using react well with these drugs. Also, make them aware of disorders you are suffering from such as epilepsy and liver and kidney disorders among other diseases react undesirably with Cetirizine and Loratadine.

Side effects of Cetirizine and Loratadine

Sleepiness in about 14% of patients, presence of cotton mouth, fatigue, nausea, headache, sore throat, and jitteriness are among the commonly reported effects of Cetirizine. The adverse yet rare adverse effects of Cetirizine include seizures, allergic reactions, low blood pressure, and fainting. In the Loratadine tablets, the side effects, such as headaches, dry mouth, drowsiness, and fatigue, are common. Recently, adverse reactions such as insomnia and nervousness have been reported. The side effects experienced in both drugs should be treated with the medical magnitude they deserve. The surest way to avoid the aforementioned side effects is however to read and understand the usage instructions and adhere to the doctor's prescription.


These two drugs are used to treat seasonal allergic conditions. Besides treating allergic conditions, Cetirizine can be used to treat other disorders like Kimura and Rhinovirus infection. Also, it can be used by persons of all ages with a doctor's prescription. Loratadine is can also be used to treat eczema, but it is age restricted. The primary drawback of Cetirizine and Loratadine is that they bare some adverse effects but these side effects can easily be avoided by following the medical prescriptions and stopping the medication once you notice it is not working well with your immune system. In such occasions, contact your doctor immediately for proper guidance. While the treatment may be discontinued, alternative medicine may be prescribed to manage the conditions.