Montelukast and neuropsychiatric reactions: mood, sleep and behaviour

Montelukast is a leukotriene receptor antagonist used to prevent asthma symptoms and to treat some allergic conditions. In its drug safety update, the MHRA explained that neuropsychiatric reactions have been known for some time and are listed in the product information. A review by European regulators confirmed the known risks and found that the magnitude of the risk was unchanged, but it identified cases in which recognising the reaction as a possible drug effect had been delayed.

That delay is the reason for the reminder. Mood and sleep changes in a child or teenager can easily be put down to growing up, school pressure or the illness itself. The MHRA asks prescribers to be alert and to weigh carefully the benefits and risks of continuing treatment if such reactions occur.

The MHRA lists sleep disturbances, depression and agitation as possibly affecting up to 1 in 100 people taking montelukast, disturbances of attention or memory in up to 1 in 1,000, and, very rarely, hallucinations and suicidal behaviour in up to 1 in 10,000. It also asked prescribers to be aware of speech impairment such as stuttering and obsessive-compulsive symptoms as newly recognised reactions.

The NHS lists a similar set of warning signs for patients: anxiety, depression or aggression, seeing things that are not there, difficulty concentrating or remembering, new or worsening sleep problems such as nightmares or sleepwalking, changes in speech or stuttering, and shaking or trembling.

Parents often see the change before the child can describe it. A child who starts waking with night terrors, becomes unusually clingy, irritable, withdrawn or aggressive, or starts a new tic or stutter after beginning montelukast deserves a conversation with the prescriber. The NHS advises telling family and friends that montelukast may affect mood, sleep or behaviour, so that others can help notice any changes. Teachers and other carers can be told as well.

Keeping a short diary of dates, symptoms and when doses were taken makes the link easier to assess. Because asthma itself can disturb sleep, the prescriber will consider whether the symptoms predate the tablet.

The MHRA tells patients and carers not to stop montelukast without talking to a doctor or asthma nurse first. That is because stopping can leave asthma less well controlled, and the prescriber can offer alternative treatment. In the NHS advice, mood or behaviour changes call for contacting the doctor or 111 straight away, and thoughts about harming yourself need an emergency response through 999 or A&E.

The clinician will review whether the benefits of the drug still outweigh the risks, may stop it or switch to another preventer, and will document the reaction. Most people who stop their medicine recover, but the evidence base is observational, so decisions are individual.

The MHRA noted that, in the UK between 2014 and 2018, it received 219 reports of suspected neuropsychiatric reactions through the Yellow Card scheme while there were approximately 14 million prescriptions of montelukast. Since the medicine was first marketed in the UK it had received 639 such reports. Those figures are reports of suspected reactions, not confirmed cases, and are a reminder of how rare these events are compared with how often the drug is used.

Patients, parents and carers can submit their own report through the Yellow Card website or app. Details of when symptoms began and what happened after stopping are most useful.

Uncontrolled asthma carries its own dangers, so the aim is not to avoid montelukast out of fear but to use it knowing the signs. Review it at asthma check-ups, ask about sleep and mood, and revisit it if concerns arise. The NHS also lists liver problems, an unusual heartbeat and a flu-like illness with numbness or worsening asthma among reasons to call a doctor, which are separate from the mental health effects.