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This cycle of drug abuse is something public health consultant Professor Rachel Isba also sees in her new clinic for under 16s experiencing the physical side effects of ketamine use.

Prof Isba says the first signs of ketamine bladder are severe abdominal pains, urinating blood and jelly from the damaged bladder lining.

"The children that come to see me have to want to see me and understand why they are here," Prof Isba says.

Prof Isba offers nicotine replacement therapy – such as gums and patches – and talks to them about how vaping affects their lives.

Professor Rachel Isba, who is leading the vaping service at Alder Hey, told a safety and quality assurance committee last year that more data was needed on the number of children addicted to nicotine.