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.
It has been associated with night terrors, depression and in rare cases hallucinations or suicidal behaviour.
The Medicines and Healthcare products Regulatory Agency (MHRA) confirmed this weekend it was reviewing the drug’s risks after identifying “further concerns”.
Tanya Hinder, from the montelukast UK action group, 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 UK action group for the drug, which represents 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 to be reopened.
Jenny Llewellyn, 33, a nursery teaching assistant, said her daughter Lottie was prescribed the drug when she was just three. It appeared to trigger abrupt changes in her behaviour. “Everything was doom and gloom,” said Llewellyn. “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 as young as six months old.
In the US, the drug has had a black box warning since 2020, the highest safety warning 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.
On 21 February, Letitia James, the New York attorney general, wrote to the FDA, urging it to take “immediate action” over the drug, which is 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. It also highlighted at that time 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.”
Dr Andy Whittamore, clinical lead at Asthma+Lung UK, said: “Montelukast is usually a very safe medication. It is important that doctors explain its possible side effects.”
