Montelukast is a cysteinyl leukotriene type-1 receptor antagonist used in the treatment of asthma as an ‘add-on’ therapy where symptoms are inadequately controlled with use of an inhaled corticosteroid and a short acting β-agonist. Montelukast is also licensed as an alternative treatment to low-dose inhaled corticosteroids for people with mild persistent asthma and no recent history of serious asthma attacks requiring oral corticosteroid use, or who cannot use inhaled corticosteroids; for the prophylaxis of asthma in which the predominant component is exercise-induced bronchoconstriction; and for symptomatic relief of seasonal allergic rhinitis in people with asthma.
There is no good evidence that montelukast exposure during pregnancy is associated with an increased risk of infant congenital malformation. A possible association between montelukast exposure and limb reduction defects identified from early spontaneous reports provided to the manufacturer of montelukast was not reproduced in a subsequent study. The data relating to risks of miscarriage, stillbirth, low infant birth weight and premature delivery are limited, and although there is currently no reliable evidence of any increased risks, further studies are required to confirm these findings.
Uncontrolled maternal asthma has been associated with a number of adverse pregnancy outcomes, including fetal loss, preterm birth and low infant birth weight, as well as adverse maternal events such as preeclampsia. Where clinically indicated, continued maternal treatment with montelukast in pregnancy is likely to outweigh any theoretical risk posed to the fetus. Montelukast therapy should not be discontinued on account of pregnancy without careful consideration of the risk to both mother and fetus of uncontrolled maternal asthma.
Exposure to montelukast at any stage in pregnancy would not usually be regarded as medical grounds for termination of pregnancy. However, other risk factors may be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments.
This is a summary of the full UKTIS monograph for health care professionals and should not be used in isolation. The full UKTIS monograph and access to any hyperlinked related documents is available to NHS health care professionals who are logged in.
If you have a patient with exposure to a drug or chemical and require assistance in making a patient-specific risk assessment, please telephone UKTIS on 0344 892 0909 to discuss the case with a teratology specialist.
If you would like to report a pregnancy to UKTIS please click here to download our pregnancy reporting form. Please encourage all women to complete an online reporting form.