Safety fears over asthma drug after young children suffer severe side effects

Children as young as three have suffered traumatic side effects from a blockbuster asthma drug now under review by the UK drugs regulator.

Families say asthma patients, including many children, are not properly warned of the risks from the commonly prescribed drug, montelukast, which has been associated with night terrors, depression and, in rare cases, hallucinations or suicidal behaviour.

The Medicines and Healthcare products Regulatory Agency (MHRA) has confirmed that it is reviewing the drug’s risks after identifying “further concerns.”

A member of the montelukast UK action group, Tanya Hinder, said: “Those affected have reported uncontrollable aggression, children attacking family members and suffering very intrusive thoughts. Tragically, there have also been attempted and reported suicides.”

The action group, which has nearly 3,500 members, is campaigning for more prominent warnings, stricter controls and support for those affected. It says patients should first consult a doctor if they have any concerns.

Graham and Alison Miller, whose son Harry, an asthma sufferer, took his life aged 14 in February 2018 while on the drug, are among the families calling for action. They learned of montelukast’s possible side effects two years after their son’s death and want his inquest reopened.

Jenny Llewellyn, 33, a nursery teaching assistant, said her daughter, Lottie, was prescribed the drug when she was three years old. It appeared to trigger abrupt changes in her behaviour. She said: “Everything was doom and gloom. She would go to bed crying and wake up crying.”

The breakthrough asthma and allergies drug was launched by the pharmaceutical giant, Merck, in 1998. It stops airways from narrowing and helps to prevent asthma attacks. The side effects of the drug, including behaviour and mood changes, are listed in the patient information sheet, but campaigners say the warnings should be printed on the packet and flagged by health professionals.

There were 4.3m montelukast prescriptions in 2022/23 in England, at a cost of £6.69m.

The action group estimates that about 350,000 patients are prescribed the drug in England, including more than 35,000 children, based on an analysis of NHS data. It can be given to babies from six months old.

In the US, the drug has had a black box warning since 2020, the highest safety alert drugs can be assigned by the FDA. The agency has highlighted animal studies which suggest the drug can cross the blood-brain barrier, a membrane that acts as a filter and keeps out harmful substances and pathogens.

The New York attorney general, Letitia James , wrote to the FDA urging it to take “immediate action” concerning the drug, sold under the brand name Singulair. She said “tragic adverse mental events” involving children continue to be reported.

The MHRA said clearer warnings were included in the product information about the risk of neuropsychiatric effects following a European review in 2019 which also highlighted the risks of neuropsychiatric reaction, with some side effects more frequently reported in children.

The agency said: “We are conducting a further review to consider any new data on the risk, indicators of lack of awareness with patients, carers and healthcare professionals and whether any further regulatory action is required.

“We are now in the final stages of our review. We continue to closely monitor reports of suspected neuropsychiatric adverse drug reactions with montelukast and have initiated our current review following identification of further concerns.”

Organon, a Merck spinoff responsible for montelukast in the UK, said: “Nothing is more important to Organon than the safety of our medicines and the people who use them. We continually monitor safety.

“We are confident that, in conjunction with the MHRA, we have communicated to healthcare professionals and patients complete and appropriate information regarding the safe and effective use of montelukast.”

Clinical lead at Asthma+Lung UK, Dr Andy Whittamore said: “Montelukast is usually a very safe medication but it is important that doctors explain its possible side effects.