Harry Miller was a popular teen who was admired for his sharp sense of humor, his ability to get along with anyone, and his “thirst for the next adventure.”

In the fall of 2017, he struggled with difficult thoughts and angry feelings. Harry, 14, who lives in south-west London, confided in friends and family about his inner turmoil.

“I just feel angry,” he told his mother one day. “I just went crazy and couldn’t control it. I didn’t know what was going on.”

Two years ago, Harry took the asthma medication Montelukast. Unbeknownst to his parents, a range of psychiatric reactions have been reported associated with montelukast treatment, including aggression, depression, and suicidal thoughts.

Harry’s parents, Graham Miller, chief executive of Christian charity London City Mission, and Alison were not given proper warning about potential side effects.

Their son was referred to the NHS Child and Adolescent Mental Health Service in January 2018 but he missed his appointment because it was given to the wrong person.

Harry was found dead at home on February 11, 2018, and subsequent investigations revealed that Harry committed suicide. Friends of St Cecilia’s Church of England School in Southfield, south-west London, described him as “a shining superstar” in tributes.

Two years after his death, his father saw a Medicines and Healthcare products Regulatory Agency (MHRA) warning online about the adverse effects of montelukast. It said these were rarely likely to include suicidal behaviour. Graham Miller said: “It is absolutely outrageous that parents are giving their children psychoactive substances without proper warning of the risks.”

This weekend, the MHRA confirmed the drug was under review. The UK Montelukast Action Group has called for more prominent warnings about the drug’s possible side effects.

Montelukast was first licensed for use in the UK in 1998 for the treatment of asthma and allergies. It generated more than $50 billion in global revenue for pharmaceutical company Merck, according to a Reuters analysis of company filings.

The patent on Montelukast’s brand name Singulair expired in 2012, meaning cheaper generic versions are available. It’s an effective drug and an opportunity for the NHS to save millions of pounds.

The National Institute for Health and Care Excellence (Nice) published draft guidance in December 2016 stating that leukotriene receptor antagonists (the drug class to which montelukast belongs) should be given before more expensive combination inhalers. It is estimated that for every 10,000 patients taking the drug under the new recommendations, The NHS could save £3 million a year.

The UK Montelukast Action Group unsuccessfully opposed the move, warning that the drug should be used as a “last resort” drug because of the risk of neuropsychiatric side effects.

Jenny Llewellyn, 33, a nursery assistant near Swindon, Wiltshire, said her daughter Lottie was given the drug last September when she was just three age. This seemed to trigger a sudden change in her behavior.

“She started having these horrible nightmares,” Llewellyn said. “It was such a nasty thing. Then her behavior started to change. She was hitting us. She was yelling at us.”

Llewellyn said she was “shocked” that her daughter was given the drug without being told to look out for signs of adverse side effects. After stopping the medication, her daughter is now back to her “old self,” she said.

Hannah, 45, who lives in Manchester, asked that her surname not be used. She said her daughter started taking the drug in 2015 when she was six, but she never associated her angry outbursts and hallucinations with the drug.

“She would have outbursts out of nowhere,” Hannah said. “I asked doctors and psychologists about the problems we were facing, but no one did a drug review and looked into this drug.” She said her daughter has suffered severe withdrawal symptoms since stopping treatment with montelukast. .

Tanya Hinder, of Action UK, said: “We have received reports of affected people walking in front of vehicles, jumping out of cars and climbing out of windows in extreme distress. There have been reports of people using Knife self-inflicted and threatening others.”

When the FDA reviewed data from 2008-09, it found a variety of adverse psychiatric events associated with the drug, including aggression, depression and suicidal behavior. It said some reports appeared to be consistent with effects caused by the drug. Montelukast’s information leaflet says suicidal thoughts and behaviors are possible side effects but are very rare.

A review of 59 studies published in Nature european respiratory review No increased risk of suicide was found in asthma patients taking the drug last year. The family said more research is needed.

After Harry’s death, the Millers were so concerned about the risks of the drug that they arranged a meeting with then health minister Nadine Dorries and the MHRA in February 2021. They are convinced changes will be made to ensure patients are properly informed about potential adverse side effects.

The Millers said this weekend that changes they would like to see, including risk warnings on drug packaging and better monitoring of patients taking their medications, have not yet been implemented.

Alison Miller said she was convinced drugs caused her son’s death and the couple wanted to see his inquest reopened. “A perfectly healthy, happy child died after taking this drug and nothing changed,” Alison said. “This is unacceptable.”