In the season of blooming spring, many allergy sufferers are troubled by drifting pollen and willow catkins: allergic rhinitis, allergic skin diseases, allergic asthma, etc., causing great suffering.

When allergies flare up, you usually need to take an antihistamine to relieve the symptoms. What are the differences between the common antihistamines cetirizine and loratadine found in pharmacies, and how should you choose?

Different Drug Structures ✔️

⚪️ Cetirizine and ⚫️ Loratadine are second-generation antihistamines,

⚪️ Cetirizine is a piperazine antihistamine, while ⚫️ Loratadine belongs to the tricyclic antihistamine class.

Different Applicable Ages ✔️

⚫️ Loratadine can be used in children over 2 years old and adults.

⚪️ Cetirizine (oral solution, drops) for children aged 6 months to 1 year should be used as directed by a physician; for children over 1 year and adults, use according to the package insert.

Different Dosage and Administration ✔️

For a 2-year-old child, ⚫️ Loratadine recommended dose is 5 mg/day (once daily), ⚪️ Cetirizine recommended dose is 5 mg/day (once daily or divided into two doses).

For children aged 1–2 years, ⚪️ Cetirizine recommended dose is 2.5 mg per dose, once or twice daily.

Different Onset and Duration of Action ✔️

⚪️ Cetirizine has a faster onset of action, typically taking effect within 1 hour after administration, but its duration of action is shorter than loratadine due to its shorter half-life. Cetirizine is more suitable for relieving seasonal allergic rhinitis and related symptoms.

Different Adverse Reactions ✔️

Both can cause common adverse reactions such as dry mouth and gastrointestinal discomfort.

Both have low lipid solubility, rarely cross the blood-brain barrier, and rarely cause drowsiness.

However, when comparing the two, the sedative effect of ⚪️ cetirizine is stronger than that of ⚫️ loratadine, so it is often recommended to be taken at bedtime.

Different Drug Interactions ✔️

⚪️ Cetirizine is more affected by food and other medications, with a known total of 244 drugs interacting with it.

⚫️ Loratadine has known interactions with only 83 drugs. Alcohol can increase the neurological side effects of cetirizine, such as dizziness and drowsiness, but no interaction has been observed between alcohol and loratadine.

Different Metabolic Pathways ✔️

⚪️ Cetirizine is 70% excreted unchanged in urine, undergoes minimal hepatic metabolism, and has fewer drug interactions.

⚫️ Loratadine is largely metabolized in the liver to desloratadine, a process that requires hepatic enzyme metabolism.

Different High-Dose Safety Profiles ✔️

In animal studies, even long-term administration of very high doses of

⚪️ cetirizine did not increase cancer risk or reduce fertility, but long-term administration of very high doses of

⚫️ loratadine was associated with an increased risk of cancer and reduced fertility in male animals.