The DRINK trial

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Results from the DRINK study show that it will be possible to run a large trial testing the effect of high water intake on ADPKD progression.

The study was part funded by the PKD Charity and took place at the Addenbrooke’s Hospital.

DRINK (Determining feasibility of Randomisation to high versus ad libitum water Intake in Polycystic Kidney Disease) was designed to test whether patients would be willing to take part in a water trial over 8 weeks and keep to a daily ‘prescription’ of water.

Dr Ragada El‑Damanawi, one of the research team, explains more: “We know that cyst growth in ADPKD is stimulated by an antidiuretic hormone called vasopressin. Drinking enough water can stop the brain making vasopressin and may work just as well as medications such as tolvaptan. We needed to know if people would voluntarily drink more water than normal and achieve a target urine dilution, which we knew would suppress vasopressin. ”

Forty-two adults with ADPKD took part in the study. They were randomly divided into 2 groups: one group agreed to continue drinking as normal; the other group were asked to drink a lot more water. Participants were given dipsticks to record their urine specific gravity at home and record it on a smartphone app. This test shows how dilute or concentrated urine is. If it was too concentrated, participants were told to drink more water and if too dilute, to drink less.

At the end of 8 weeks, the results showed that most people achieved the target specific gravity and were able to adhere to a fluid prescription. There were no harmful effects on kidney function during the study.

The research team is now looking at how to run a larger, longer trial. Despite water being potentially a low-cost therapy for treating ADPKD, finding the money for a major clinical trial is proving a challenge.