Cetirizine vs. Levocetirizine — What's the Difference?

Cetirizine and levocetirizine are closely related medications used to manage symptoms of allergic reactions, such as sneezing, itching, watery eyes, and runny nose. Both belong to the second-generation antihistamines, which are preferred over first-generation antihistamines due to their reduced sedative effects, meaning they are less likely to make you feel drowsy.

Cetirizine is a racemic mixture, meaning it contains two isomers (enantiomers) that are mirror images of each other. One of these enantiomers is levocetirizine, which is considered the more active form of the drug, responsible for most of the antihistaminic effects. By isolating levocetirizine, manufacturers aim to provide a medication that can achieve the desired effects at a lower dose, potentially reducing the likelihood of side effects.

While cetirizine is effective and widely used, levocetirizine may offer advantages in terms of potency and side effect profile. Some studies suggest that levocetirizine can be more effective at lower doses than cetirizine, which can be beneficial for patients sensitive to medication effects or those looking for a potent antihistamine with minimal sedative properties.

Both medications work by blocking the action of histamine, a substance in the body that causes allergic symptoms. They are effective for treating seasonal allergies, such as hay fever, and perennial allergic conditions, like dust or pet allergies. However, due to its higher potency, levocetirizine might be chosen for individuals who do not achieve sufficient relief from cetirizine or who experience bothersome side effects at higher doses of cetirizine.

The choice between cetirizine and levocetirizine often depends on individual response, the severity of symptoms, and potential side effects. Both medications are well-tolerated by most individuals, but as with any medication, discussing options with a healthcare provider is essential to determine the most appropriate treatment.