The NICE and SMC guidance on tolvaptan says that patients should have ‘evidence of rapidly progressing disease’ to be considered for tolvaptan treatment. So, what does this mean? UK kidney experts have developed a guide for kidney specialists to help them judge whether a person’s ADPKD is progressing quickly. The guidance is very detailed, but in essence they say that you may have rapidly progressing disease if you meet one of the following criteria:

• The amount of waste that your kidneys can filter from your blood is notably decreasing each year. This is calculated from blood tests that measure your eGFR
• Scans show that your kidneys have increased in size over the last 6 to 12 months
• Your medical history shows there’s a high risk your ADPKD will progress quickly (for example, this could be based on your scan results, the particular genes causing your ADPKD, or your family history)

You may want to ask your kidney specialist how quickly they think your ADPKD will progress, and to explain what they are basing this on. Your kidney specialist or other doctor may not be able to tell you this immediately, because they may require the results of further investigations (blood or imaging tests).

Yes. If you’re already taking tolvaptan, your kidney specialist or other doctor can continue to prescribe it to you until you decide together that it’s the right time to stop.

Tolvaptan works by blocking a hormone called vasopressin in your body. Vasopressin has a few roles in your body, including controlling the amount of water you retain. By counteracting vasopressin, tolvaptan can reduce the levels of a natural chemical, cyclic AMP, in the kidney that encourages cysts to grow. This can help to slow the speed at which your kidney function declines.

A clinical trial (TEMPO 3/4) tested how well tolvaptan works compared with placebo (a ‘dummy’ pill) for patients with rapidly progressing ADPKD. After 3 years, patients taking tolvaptan had kidneys that had enlarged at half the rate of those taking placebo. Tolvaptan also reduced the rate at which patients’ kidney function got worse. This is very promising and is the first treatment to directly tackle ADPKD and provide a direct benefit to patients with ADPKD.

The side-effects of tolvaptan include:

• Being thirsty and having to drink more water
• Passing more urine in the day and night
• Changes in liver function tests: less than 1 in 100 patients in trials showed severe changes in the blood tests for liver function. These changes reversed on stopping tolvaptan, but if they had gone unnoticed, they might have caused serious liver problems. As a result, ALL patients being treated with tolvaptan will need regular monitoring of their liver function (i.e. tests at least once a month).

For many people, the benefits of tolvaptan will outweigh the disadvantages. But in the main clinical trial, about 23 in every 100 patients stopped taking tolvaptan because of the side-effects.

If you’re taking tolvaptan, you’ll have regular monitoring to check your liver health.

Tolvaptan is not recommended if you have stage 4 or 5 kidney disease. If you have stage 4 or 5 kidney disease, your kidneys have already been damaged. You won’t benefit from tolvaptan, as it cannot reverse damage already done.

NICE in England and the SMC in Scotland use slightly different criteria to make recommendations about medicine prescriptions, so sometimes their advice can differ. The NICE experts who reviewed tolvaptan did not believe there was enough proof that patients with stage 1 disease benefited from tolvaptan to justify the cost of treatment. To make things clearer and to give extra advice to doctors, the Renal Association Working Group on Tolvaptan has developed additional guidance.