A popular asthma tablet linked to cases of suicidal thoughts and depression in children will now be sold with side effect warnings inside its packaging.

Key points: Warnings about side effects of Montelukast and Singulair to be included in boxes

Warnings about side effects of Montelukast and Singulair to be included in boxes Advice to be added to education for health professionals

Advice to be added to education for health professionals Parents happy but say measures don't go far enough

The drug, known as Montelukast or Singulair, is prescribed for children aged two to 14 with frequent intermittent, mild persistent or exercise-induced asthma.

In 2017, the ABC revealed parental concerns about the medication.

Vanessa Sellick's son Harrison had been taking the drug since he was two years old and suffered serious behavioural changes.

"Harrison was four years old when he started making comments about wanting to die, wishing that he was dead, that he was a piece of garbage — he had terrible self-loathing," Ms Sellick said.

"It was just devastating at the time."

She has been campaigning to have better warnings about the drug, as well as more education for doctors.

Following a review of its safety, the Therapeutic Goods Administration (TGA) has decided that information about the drug's side effects should be included in boxes.

The TGA also wants health authorities to include warnings in guidelines for health professionals, and called for better monitoring of how many kids might be suffering serious side effects.

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It's step in right direction, 'but not enough'

Ms Sellick said she was pleased with the decision, but wanted the Government to go further.

"Although these outcomes are a step in the right direction, they are not enough," she said.

"This medication has been linked to death by suicide."

Vanessa Sellick and her son Harrison are pleased with the decision, but believe more can be done. ( Supplied )

Parents had wanted warning labels on the outside of Montelukast's packaging.

"Warning labels are vital in ensuring patients or their carers are reminded to constantly monitor for changes in mood and behaviour," Ms Sellick said.

"Without these labels we fear that many families will not make the link between the side effects and Montelukast."

Harrison, who's now 12, said he was "extremely disappointed" that compulsory warning labels were not included.

After the ABC raised the issue, many more parents spoke up about their children's experiences with the drug.

TGA review found evidence of link

Dr Tim Greenaway, chief medical adviser to the TGA, said they were updating their advice to doctors and patients after reviewing the medical literature.

"We came to the conclusion that there is an association between Montelukast and neuropsychiatric side effects, but we can't say that it is causal," he told the ABC.

He said between 2000 and December 2017, there were 167 adverse neuro-psychiatric side effects in children and adolescents taking the drug.

Paediatric respiratory physician Adam Jaffe, from Sydney Children's Hospital, said there was no way of knowing which children might suffer a reaction to the medication.

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He has taken some of his own patients off the drug because they experienced serious side effects.

"Some of my patients complained of nightmares, tantrums, being angry or sad, and the challenge for me and the parents is to figure out whether it's the medication or the child's behaviour," he said.

He stressed the majority of patients could take it safely, but said some children could suffer the psychiatric side effects.

American health authorities have been investigating the safety of Montelukast since 2008 following the death of a teenager there.

Cody Miller, 15, took his own life after taking the drug for just 17 days.

The US Food and Drug Administration (FDA) now requires manufacturers to put warnings about psychiatric side effects in medical information.

Drug used safely by tens of millions, company says

When the ABC first raised concerns about the medication, the company behind Singulair — Merck, Sharp and Dohme (MSD) — said it had been used safely by tens of millions of people around the world.

"Consumer medicine information is made available to patients via the TGA website or the MSD website," it said.

In a written statement, a spokeswoman said the company had not found any further safety information relating to suicidal thoughts or depression which it would need to relay to users.

"Montelukast, an asthma medication, is manufactured by six companies in Australia," she said.

"MSD has not identified any additional safety information in relation to neuropsychiatric adverse events to communicate to prescribers or patients.

"We are currently liaising with the TGA, and we are committed to working with [the] Government to provide relevant information about Montelukast and its side effects."