Only one in eight long-term ketamine users recover from urinary problems incurred by the drug, a recent study has shown.
The results also found the length of time someone had been using ketamine affected the degree of bladder-function recovery after treatment.
Chinese University analysed 271 patients at the Youth Urological Treatment Centre after an average of 10 months since they received treatment.
Only 12.8 per cent of patients who exceeded the normal score on the Pelvic Pain and Urgency/Frequency Patient Symptom Scale returned to normal levels.
Ketamine can cause irreversible bladder fibrosis, incontinence and chronic bladder pain, permanently lower bladder capacity and damage the bladder's urinary function.
"Only ketamine causes this many problems with voiding," said centre director Professor Anthony Ng Chi-fai.
The findings showed 77.4 per cent of patients had a voiding capacity of less than 150cc, the normal minimum, with 25.1 per cent normalising after treatment.
Sixty-five per cent had a maximal flow rate slower than 15cc per second, 30.7 per cent of whom normalised after treatment.
Seventy-eight per cent had a bladder capacity of less than 200cc, 21.1 per cent of whom normalised after treatment.
The average age of the patients was 25, 60 per cent were female and the average length of drug use was 80 months.
"Ketamine is now one of the main drugs used in Hong Kong because it is relatively cheap and quite easily available," Ng said.
Last year, police and customs seized 724kg of the drug and recorded 1,677 ketamine-related cases.
He said ketamine had only been used recreationally for the past decade and therefore little was known about the long-term effects of the drug.
In response to the findings, Ng and two dozen other frontline health-care professionals formed the Hong Kong Substance Abuse Medical Alliance to advocate early identification of, and intervention in, cases of psychotropic substance abusers.
He said drug addicts typically lacked motivation to seek help and often held the misbelief they could control their drug use and quit any time.
Ng said the alliance would speak at schools and supported the government's proposal to make police screen suspected drug users and take them to clinics.