Yes, montelukast and levocetirizine can be taken together safely. This combination is widely used and even recommended by international allergy guidelines (ARIA) for treating conditions like allergic rhinitis and asthma. The two drugs work through completely different pathways, and their combined effect on allergy symptoms is greater than either drug alone.
Why the Combination Works
Montelukast and levocetirizine target two separate branches of the allergic response. Levocetirizine is an antihistamine that blocks histamine, the chemical responsible for sneezing, itching, and a runny nose. Montelukast blocks leukotrienes, a different set of inflammatory chemicals that cause nasal congestion, swelling, and mucus production. Because allergies trigger both histamine and leukotrienes at the same time, blocking only one pathway often leaves symptoms partially uncontrolled.
Together, the two medications also reduce several inflammatory signals beyond just histamine and leukotrienes. They lower levels of multiple proteins involved in tissue swelling and immune cell migration, which is why the combination tends to provide noticeably better relief than either drug on its own. In a phase III clinical trial of patients with both asthma and allergic rhinitis, the combination produced significantly greater reductions in daytime nasal symptoms compared to montelukast alone.
How to Take Them
In clinical studies, the combination is typically taken once daily in the evening. Montelukast for asthma is specifically recommended as an evening dose. For allergic rhinitis alone, montelukast can technically be taken at any time of day, but evening dosing keeps things simple and consistent. Levocetirizine reaches its peak blood level in about one hour, so it starts working relatively quickly.
Both medications can be taken with or without food. In pediatric studies (children ages 6 to 14), the standard combination was 5 mg of montelukast plus 5 mg of levocetirizine, taken together each evening for four weeks. Adult doses follow a similar once-daily pattern. Fixed-dose combination tablets that contain both drugs in a single pill are available in some countries, which simplifies the routine.
Side Effects to Watch For
Levocetirizine is a third-generation antihistamine, meaning it causes less drowsiness than older options like diphenhydramine. That said, some people still experience mild sleepiness, which is one reason evening dosing makes sense. Alcohol can amplify this drowsiness, so it’s worth being cautious with drinks while on levocetirizine.
Montelukast carries a more significant safety consideration. The FDA added its strongest warning label to montelukast in 2020 due to reports of neuropsychiatric side effects. These can include mood changes, irritability, vivid or bad dreams, trouble sleeping, anxiety, depression, confusion, and in rare cases, suicidal thoughts or hallucinations. Other reported effects include restlessness, attention problems, sleepwalking, and tremor. These side effects are uncommon but serious enough that you should stop the medication and contact a healthcare provider if you notice any behavioral or mood changes. In a study of children taking both drugs for asthma and allergic rhinitis, nightmares occurred in about 7% and sleep disturbances in about 4%.
A Note on Combined Tablets
If you’re taking these as separate pills, there’s no interaction that makes the combination dangerous. However, pharmaceutical research has found something interesting about the physical tablets themselves: when the raw ingredients of montelukast and levocetirizine are in direct contact (as in a single combined pill), a chemical reaction can cause the tablet to change color and develop higher impurity levels over time. This is a manufacturing challenge, not a safety issue for you as a patient. Properly formulated combination tablets solve this by keeping the two drugs physically separated within the pill using different granulation layers and stabilizers.
Whether you take them as two separate pills or a single combination tablet, the drugs themselves do not interfere with each other’s absorption or effectiveness in your body. The combination is one of the more straightforward pairings in allergy management, which is why it’s become a standard approach for people whose symptoms don’t respond well enough to a single medication.