Medication for excessive urine production in patients treated with tolvaptan

1. Diagnosis of ADPKD, based upon modified Ravine criteria

2. Using tolvaptan 120mg daily

3. Age between 18 and 50 years

4. >45 eGFR (CKD-EPI)

5. Providing informed consent

1. Patients who, in the opinion of the investigator may present a safety risk

2. Patients who are unlikely to adequately comply to the trial¡¯s procedures (due for instance to medical conditions likely to require interruption or discontinuation, history of substance abuse or non-compliance)

3. a. Patients taking medication likely to confound endpoint assessments (e.g. NSAID or diuretics such as furosemide or spironolactone)

3. b. Patients having concomitant illnesses likely to confound endpoint assessments such (e.g. diabetes mellitus for which medication is needed or diabetes insipidus)

4. Women who are pregnant or breastfeeding

5. Patients with known contra indications to the study medication such as

5. a. Hydrochlorothiazide: gout, hepatic impairment, illnesses that cause potassium loss, history of hypokalaemia, known allergy to hydrochlorothiazide

5. b. Metformin: Illnesses that can cause tissue hypoxia (e.g. recent myocardial infarction, heart failure, respiratory failure), known allergy to metformin