Is levocetirizine + montelukast safe during breastfeeding?

Levocetirizine + Montelukast Safety During Breastfeeding

Both levocetirizine and montelukast are compatible with breastfeeding based on very low transfer into breast milk and absence of reported harm to infants. 1, 2

Individual Drug Safety Profile

Levocetirizine

• Transfer into breast milk is minimal, with a weight-adjusted relative infant dose (RID) of only 1.9% and absolute infant dose of 1.1 μg/kg per day 1
• Maximum milk concentrations occur approximately 2.4 hours after maternal intake, with a mean half-life in milk of 7.0 hours 1
• No severe adverse events have been reported in breastfed infants exposed to levocetirizine 1
• The FDA label states breastfeeding is "not recommended," but this reflects lack of data rather than evidence of harm 3

Montelukast

• Excretion into breast milk is extremely low, with only about 1% of the maternal dose passing into milk 4
• The relative infant dose is 0.68% of the maternal dose, with average milk levels of 5.3 ng/mL and maximum concentration of 9.7 ng/mL at 4 hours post-dose 2
• Extensive metabolism and plasma protein binding further limit infant exposure 4
• Expert consensus states that the benefits of breastfeeding overwhelm the risk of exposure 4

Clinical Recommendations

The combination of levocetirizine and montelukast can be used during breastfeeding based on:

• Both drugs demonstrate RID values well below the 10% safety threshold typically used to assess breastfeeding compatibility 1, 2
• Recent high-quality research (2024 for levocetirizine, 2017 for montelukast) confirms minimal transfer and safety 1, 2
• No documented adverse effects in breastfed infants 1, 2

Practical Strategies to Minimize Infant Exposure

• Consider timing breastfeeding immediately before medication intake to further reduce infant exposure, as peak milk concentrations occur 2-4 hours after maternal dosing 4, 1
• This strategy is particularly relevant for levocetirizine, which peaks at 2.4 hours 1

Important Caveats

Cetirizine and loratadine have more accumulated safety data than levocetirizine and may be preferred alternatives if switching antihistamines is feasible 5

Monitor the infant for potential sedation, though this has not been reported in published studies, as antihistamines theoretically could cause drowsiness 1

The evidence quality is stronger for montelukast (multiple guidelines and research studies) compared to levocetirizine (primarily one high-quality 2024 study), though both are acceptable 4, 5, 1, 2