A grieving Queensland woman whose son took his life days after he started taking an anti-smoking drug has said he was in great shape before the medication was prescribed.

Timothy John, 22, killed himself just eight days after he started taking Pfizer’s Champix in 2013. His mother, Phoebe Moorwood-Oldham, is campaigning for on-the-box warnings about the pills’ potential side-effects.

An inquest at the Brisbane coroner’s court is considering the role of Champix in John’s death and whether appropriate warnings were given.

John started smoking and drinking at the age of 13, and had struggled with depression and anxiety for a number of years, the inquest was told. His mother said he had “never ever spoken to me about suicide in my entire life”.

She said he had been transformed after completing a treatment program the year before his death. “It was like someone had waved a magic wand over him; he wasn’t drinking and wanted to cut his smoking.”

Moorwood-Oldham said his anxiety was minimal at the time and he was the “best he had been for years”.

He told his GP he was having trouble quitting smoking and was prescribed Champix, the inquest heard. The doctor had told him the medication might increase his anxiety but he was allegedly given no other warnings.

The night before he died, his mother found him sitting on his bedroom floor with a chainsaw in his lap, saying, “They’re coming to get me Mum, help me.”

She said the next day there were red welts on one of his arms.

Other families who have lost relatives in similar circumstances attended the inquest. John and Christine Nicholson, whose son Paul took his life in 2009 weeks after starting Champix, support the campaign.

“Paul was 35, he was just a normal person with everything to live for – he had a wife, three kids, a new house and a good job,” John Nicholson said outside the hearing.

Moorwood-Oldham won the right to an inquest after 48,000 people signed a change.org petition.

• Readers seeking support and information about suicide prevention can contact Lifeline on 13 11 14.

